:mod:`seq.alg <ost.seq.alg>` -- Algorithms for Sequences
================================================================================
.. module:: ost.seq.alg
:synopsis: Algorithms for sequences
Algorithms for Alignments
--------------------------------------------------------------------------------
.. function:: MergePairwiseAlignments(pairwise_alns, ref_seq)
:param pairwise_alns: A list of pairwise alignments
:type pairwise_alns: :class:`~ost.seq.AlignmentList`
:param ref_seq: The reference sequence
:type ref_seq: :class:`~ost.seq.SequenceHandle`
:returns: The merged alignment
:rtype: :class:`~ost.seq.AlignmentHandle`
Merge a list of pairwise alignments into a multiple sequence alignments. This
function uses the reference sequence as the anchor and inserts gaps where
needed. This is also known as the *star method*.
The resulting multiple sequence alignment provides a simple way to map between
residues of pairwise alignments, e.g. to compare distances in two structural
templates.
There are a few things to keep in mind when using this function:
- The reference sequence mustn't contain any gaps
- The first sequence of each pairwise alignments corresponds to the reference
sequence. Apart from the presence of gaps, these two sequences must be
completely identical.
- If the reference sequence has an offset, the first sequence of each pairwise alignment
must have the same offset. This offset is inherited by the first sequence of the final
output alignment.
- The resulting multiple sequence alignment is by no means optimal. For
better results, consider using a multiple-sequence alignment program such
as MUSCLE or ClustalW.
- Residues in columns where the reference sequence has gaps should not be
considered as aligned. There is no information in the pairwise alignment to
guide the merging, the result is undefined.
**Example:**
.. code-block:: python
ref_seq = ost.seq.CreateSequence('ref', 'acdefghiklmn')
seq_a1 = seq.CreateSequence('A1', 'acdefghikl-mn')
seq_a2 = seq.CreateSequence('A2', 'atd-fghikllmn')
seq_b1 = seq.CreateSequence('B1', 'acdefg-hiklmn')
seq_b2 = seq.CreateSequence('B2', 'acd---qhirlmn')
aln_a = seq.CreateAlignment()
aln_a.AddSequence(seq_a1)
aln_a.AddSequence(seq_a2)
print(aln_a)
# >>> A1 acdefghikl-mn
# >>> A2 atd-fghikllmn
aln_b = seq.CreateAlignment()
aln_b.AddSequence(seq_b1)
aln_b.AddSequence(seq_b2)
print(aln_b)
# >>> B1 acdefg-hiklmn
# >>> B2 acd---qhirlmn
aln_list = ost.seq.AlignmentList()
aln_list.append(aln_a)
aln_list.append(aln_b)
merged_aln = ost.seq.alg.MergePairwiseAlignments(aln_list, ref_seq)
print(merged_aln)
# >>> ref acdefg-hikl-mn
# >>> A2 atd-fg-hikllmn
# >>> B2 acd---qhirl-mn
.. autofunction:: ValidateSEQRESAlignment
.. autofunction:: AlignToSEQRES
.. autofunction:: AlignmentFromChainView
.. function:: Conservation(aln, assign=true, prop_name="cons", ignore_gap=false)
Calculates conservation scores for each column in the alignment, according to
the ConSurf method (Armon et al., J. Mol. Biol. (2001) 307, 447-463).
The conservation score is a value between 0 and 1. The bigger the number
the more conserved the aligned residues are.
:param aln: An alignment handle
:type aln: :class:`~ost.seq.AlignmentHandle`
:param assign: If true, the conservation scores are assigned to attached
residues. The name of the property can be changed with the *prop_name*
parameter. Useful when coloring entities based on sequence conservation.
:param prop_name: The property name for assigning the conservation to
attached residues. Defaults to 'cons'.
:param ignore_gap: If true, the dissimilarity between two gaps is increased to
6.0 instead of 0.5 as defined in the original version. Without this, a
stretch where in the alignment there is only one sequence which is
aligned to only gaps, is considered highly conserved (depending on the
number of gap sequences).
.. function:: LocalAlign(seq1, seq2, subst_weight, gap_open=-5, gap_ext=-2)
Performs a Smith/Waterman local alignment of *seq1* and *seq2* and returns
the best-scoring alignments as a list of pairwise alignments.
**Example:**
.. code-block:: python
seq_a = seq.CreateSequence('A', 'acdefghiklmn')
seq_b = seq.CreateSequence('B', 'acdhiklmn')
alns = seq.alg.LocalAlign(seq_a, seq_b, seq.alg.BLOSUM62)
print(alns[0].ToString(80))
# >>> A acdefghiklmn
# >>> B acd---hiklmn
:param seq1: A valid sequence
:type seq1: :class:`~ost.seq.ConstSequenceHandle`
:param seq2: A valid sequence
:type seq2: :class:`~ost.seq.ConstSequenceHandle`
:param subst_weigth: The substitution weights matrix
:type subst_weight: :class:`SubstWeightMatrix`
:param gap_open: The gap opening penalty. Must be a negative number
:param gap_ext: The gap extension penalty. Must be a negative number
:returns: A list of best-scoring, non-overlapping alignments of *seq1* and
*seq2*. Since alignments always start with a replacement, the start is
stored in the sequence offset of the two sequences.
.. function:: GlobalAlign(seq1, seq2, subst_weight, gap_open=-5, gap_ext=-2)
Performs a Needleman/Wunsch global alignment of *seq1* and *seq2* and returns
the best-scoring alignment.
**Example:**
.. code-block:: python
seq_a = seq.CreateSequence('A', 'acdefghiklmn')
seq_b = seq.CreateSequence('B', 'acdhiklmn')
alns = seq.alg.GlobalAlign(seq_a, seq_b, seq.alg.BLOSUM62)
print(alns[0].ToString(80))
# >>> A acdefghiklmn
# >>> B acd---hiklmn
:param seq1: A valid sequence
:type seq1: :class:`~ost.seq.ConstSequenceHandle`
:param seq2: A valid sequence
:type seq2: :class:`~ost.seq.ConstSequenceHandle`
:param subst_weigth: The substitution weights matrix
:type subst_weight: :class:`SubstWeightMatrix`
:param gap_open: The gap opening penalty. Must be a negative number
:param gap_ext: The gap extension penalty. Must be a negative number
:returns: Best-scoring alignment of *seq1* and *seq2*.
.. function:: ShannonEntropy(aln, ignore_gaps=True)
Returns the per-column Shannon entropies of the alignment. The entropy
describes how conserved a certain column in the alignment is. The higher
the entropy is, the less conserved the column. For a column with no amino
aids, the entropy value is set to NAN.
:param aln: Multiple sequence alignment
:type aln: :class:`~ost.seq.AlignmentHandle`
:param ignore_gaps: Whether to ignore gaps in the column.
:type ignore_gaps: bool
:returns: List of column entropies
.. function:: SemiGlobalAlign(seq1, seq2, subst_weight, gap_open=-5, gap_ext=-2)
Performs a semi-global alignment of *seq1* and *seq2* and returns the best-
scoring alignment. The algorithm is Needleman/Wunsch same as GlobalAlign, but
without any gap penalty for starting or ending gaps. This is prefereble
whenever one of the sequences is significantly shorted than the other.
This make it also suitable for fragment assembly.
**Example:**
.. code-block:: python
seq_a = seq.CreateSequence('A', 'abcdefghijklmnok')
seq_b = seq.CreateSequence('B', 'cdehijk')
alns = seq.alg.GlobalAlign(seq_a, seq_b, seq.alg.BLOSUM62)
print(alns[0].ToString(80))
# >>> A abcdefghijklmnok
# >>> B --cde--hi-----jk
alns = seq.alg.SemiGlobalAlign(seq_a, seq_b, seq.alg.BLOSUM62)
print(alns[0].ToString(80))
# >>> A abcdefghijklmnok
# >>> B --cde--hijk-----
:param seq1: A valid sequence
:type seq1: :class:`~ost.seq.ConstSequenceHandle`
:param seq2: A valid sequence
:type seq2: :class:`~ost.seq.ConstSequenceHandle`
:param subst_weigth: The substitution weights matrix
:type subst_weight: :class:`SubstWeightMatrix`
:param gap_open: The gap opening penalty. Must be a negative number
:param gap_ext: The gap extension penalty. Must be a negative number
:returns: best-scoring alignment of *seq1* and *seq2*.
.. autofunction:: ost.seq.alg.renumber.Renumber
.. function:: SequenceIdentity(aln, ref_mode=seq.alg.RefMode.ALIGNMENT, seq_a=0, seq_b=1)
Calculates the sequence identity between two sequences at index seq_a and seq_b in
a multiple sequence alignment.
:param aln: multiple sequence alignment
:type aln: :class:`~ost.seq.AlignmentHandle`
:param ref_mode: influences the way the sequence identity is calculated. When
set to `seq.alg.RefMode.LONGER_SEQUENCE`, the sequence identity is
calculated as the number of matches divided by the length of the longer
sequence. If set to `seq.alg.RefMode.ALIGNMENT` (the default), the sequence
identity is calculated as the number of matches divided by the number of
aligned residues.
:type ref_mode: int
:param seq_a: the index of the first sequence
:type seq_a: int
:param seq_b: the index of the second sequence
:type seq_b: int
:returns: sequence identity in the range 0 to 100.
:rtype: float
.. function:: SequenceSimilarity(aln, subst_weight, normalize=false, seq_a=0, seq_b=1)
Calculates the sequence similarity between two sequences at index seq_a and seq_b in
a multiple sequence alignment.
:param aln: Multiple sequence alignment
:type aln: :class:`~ost.seq.AlignmentHandle`
:param subst_weight: the substitution weight matrix
(see the :ref:`BLOSUM Matrix<blosum>` section below)
:type subst_weight: :class:`~SubstWeightMatrix`
:param normalize: if set to True, normalize to the range of the
substitution weight matrix
:type normalize: bool
:param seq_a: the index of the first sequence
:type seq_a: int
:param seq_b: the index of the second sequence
:type seq_b: int
:returns: sequence similarity
:rtype: float
.. _substitution-weight-matrices:
Substitution Weight Matrices and BLOSUM Matrices
--------------------------------------------------------------------------------
.. autoclass:: SubstWeightMatrix
:members:
.. _blosum:
Four preset BLOSUM (BLOcks SUbstitution Matrix) matrices are available at
different levels of sequence identity:
- BLOSUM45
- BLOSUM62
- BLOSUM80
- BLOSUM100
Two naive substitution matrices:
- IDENTITY: Matches have score of 1, all other are 0
- MATCH: Matches have score of 1, all other are -1
Nucleotide substitution matrices:
- NUC44: Nucleotide substitution matrix used in blastn that can deal with IUPAC
ambiguity codes. ATTENTION: has been edited to explicitely encode T/U
equivalence, i.e. you can just do `m.GetWeight('G', 'U')` instead of first
translating 'U' to 'T'.
.. _contact-prediction:
Contact Prediction
--------------------------------------------------------------------------------
This is a set of functions for predicting pairwise contacts from a multiple
sequence alignment (MSA). The core method here is mutual information which uses
coevolution to predict contacts. Mutual information is complemented by two other
methods which score pairs of columns of a MSA from the likelyhood of certain
amino acid pairs to form contacts (statistical potential) and the likelyhood
of finding certain substitutions of aminio-acid pairs in columns of the MSA
corresponding to interacting residues.
.. class:: ContactPredictionScoreResult
Object containing the results form a contact prediction.
.. attribute:: matrix
An *NxN* :class:`~ost.FloatMatrix` where *N* is the length of the alignment.
The element *i,j* corresponds to the score of the corresponding
columns of the MSA. High scores correspond to high likelyhood of
a contact.
.. attribute:: sorted_indices
List of all indices pairs *i,j*, containing (N*N-1)/2 elements,
as the **matrix** is symmetrical and elements in the diagonal
are ignored. The indices are sorted from the pair most likely to form
a contact to the least likely one.
.. method:: GetScore(i,j)
returns **matrix(i,j)**
:param i: First index
:param j: Second index
:type i: :class:`int`
:type j: :class:`int`
.. method:: SetScore(i,j,score)
Sets **matrix(i,j)** to **score**
:param i: First index
:param j: Second index
:param score: The score
:type i: :class:`int`
:type j: :class:`int`
:type score: :class:`float`
.. autofunction:: PredictContacts
.. function:: CalculateMutualInformation(aln, \
weights=LoadConstantContactWeightMatrix(), \
apc_correction=true, zpx_transformation=true, \
small_number_correction=0.05)
Calculates the mutual information (MI) from a multiple sequence alignemnt. Contributions of each pair of amino-acids are weighted using the matrix **weights** (weighted mutual information). The average product correction (**apc_correction**) correction and transformation into Z-scores (**zpx_transofrmation**) increase prediciton accuracy by reducing the effect of phylogeny and other noise sources. The small number correction reduces noise for alignments with small number of sequences of low diversity.
:param aln: The multiple sequences alignment
:type aln: :class:`~ost.seq.AlignmentHandle`
:param weights: The weight matrix
:type weights: :class`ContactWeightMatrix`
:param apc_correction: Whether to use the APC correction
:type apc_correction: :class:`bool`
:param zpx_transformation: Whether to transform the scores into Z-scores
:type zpx_transformation: :class:`bool`
:param small_number_correction: initial values for the probabilities of having a given pair of amino acids *p(a,b)*.
:type small_number_correction: :class:`float`
.. autofunction:: CalculateContactProbability
.. function:: CalculateContactScore(aln, \
weights=LoadDefaultContactWeightMatrix())
Calculates the Contact Score (*CoSc*) from a multiple sequence alignment. For each pair of residues *(i,j)* (pair of columns in the MSA), *CoSc(i,j)* is the average over the values of the **weights** corresponding to the amino acid pairs in the columns.
:param aln: The multiple sequences alignment
:type aln: :class:`~ost.seq.AlignmentHandle`
:param weights: The contact weight matrix
:type weights: :class`ContactWeightMatrix`
.. function:: CalculateContactSubstitutionScore(aln, ref_seq_index=0, \
weights=LoadDefaultPairSubstWeightMatrix())
Calculates the Contact Substitution Score (*CoEvoSc*) from a multiple sequence alignment. For each pair of residues *(i,j)* (pair of columns in the MSA), *CoEvoSc(i,j)* is the average over the values of the **weights** corresponding to substituting the amino acid pair in the reference sequence (given by **ref_seq_index**) with all other pairs in columns *(i,j)* of the **aln**.
:param aln: The multiple sequences alignment
:type aln: :class:`~ost.seq.AlignmentHandle`
:param weights: The pair substitution weight matrix
:type weights: :class`ContactWeightMatrix`
.. function:: LoadDefaultContactWeightMatrix()
:returns: *CPE*, a :class:`ContactWeightMatrix` that was calculated from a large (>15000) set of
high quality crystal structures as *CPE=log(CF(a,b)/NCF(a,b))* and then normalised so that all its elements are comprised between 0 and 1. *CF(a,b)* is the frequency of amino acids *a* and *b* for pairs of contacting residues and *NCF(a,b)* is the frequency of amino acids *a* and *b* for pairs of non-contacting residues. Apart from weights for the standard amino acids, this matrix gives a weight of 0 to all pairs for which at least one amino-acid is a gap.
.. function:: LoadConstantContactWeightMatrix()
:returns: A :class:`ContactWeightMatrix`. This matrix gives a weight of one to all pairs of
standard amino-acids and a weight of 0 to pairs for which at least one amino-acid is a gap.
.. function:: LoadDefaultPairSubstWeightMatrix()
:returns: *CRPE*, a :class:`PairSubstWeightMatrix` that was calculated from a large (>15000) set of
high quality crystal structures as *CRPE=log(CRF(ab->cd)/NCRF(ab->cd))* and then normalised so that all its elements are comprised between 0 and 1. *CRF(ab->cd)* is the frequency of replacement of a pair of amino acids *a* and *b* by a pair *c* and *d* in columns of the MSA corresponding to contacting residues and *NCRF(ab->cd)* is the frequency of replacement of a pair of amino acids *a* and *b* by a pair *c* and *d* in columns of the MSA corresponding to non-contacting residues. Apart from weights for the standard amino acids, this matrix gives a weight of 0 to all pair substitutions for which at least one amino-acid is a gap.
.. class:: PairSubstWeightMatrix(weights, aa_list)
This class is used to associate a weight to any substitution from one amino-acid pair *(a,b)* to any other pair *(c,d)*.
.. attribute:: weights
A :class:`~ost.FloatMatrix4` of size *NxNxNxN*, where *N=len(aa_list)*
.. attribute:: aa_list
A :class:`CharList` of one letter codes of the amino acids for which weights are found in the **weights** matrix.
.. class:: ContactWeightMatrix(weights, aa_list)
This class is used to associate a weight to any pair of amino-acids.
.. attribute:: weights
A :class:`~ost.FloatMatrix` of size *NxN*, where *N=len(aa_list)*
.. attribute:: aa_list
A :class:`CharList` of one letter codes of the amino acids for which weights are found in the **weights** matrix.
Get and analyze distance matrices from alignments
--------------------------------------------------------------------------------
Given a multiple sequence alignment between a reference sequence (first sequence
in alignment) and a list of structures (remaining sequences in alignment with an
attached view to the structure), this set of functions can be used to analyze
differences between the structures.
**Example:**
.. code-block:: python
# SETUP: aln is multiple sequence alignment, where first sequence is the
# reference sequence and all others have a structure attached
# clip alignment to only have parts with at least 3 sequences (incl. ref.)
# -> aln will be cut and clip_start is 1st column of aln that was kept
clip_start = seq.alg.ClipAlignment(aln, 3)
# get variance measure and distance to mean for each residue pair
d_map = seq.alg.CreateDistanceMap(aln)
var_map = seq.alg.CreateVarianceMap(d_map)
dist_to_mean = seq.alg.CreateDist2Mean(d_map)
# report min. and max. variances
print("MIN-MAX:", var_map.Min(), "-", var_map.Max())
# get data and json-strings for further processing
var_map_data = var_map.GetData()
var_map_json = var_map.GetJsonString()
dist_to_mean_data = dist_to_mean.GetData()
dist_to_mean_json = dist_to_mean.GetJsonString()
.. function:: ClipAlignment(aln, n_seq_thresh=2, set_offset=true, \
remove_empty=true)
Clips alignment so that first and last column have at least the desired number
of structures.
:param aln: Multiple sequence alignment. Will be cut!
:type aln: :class:`~ost.seq.AlignmentHandle`
:param n_seq_thresh: Minimal number of sequences desired.
:type n_seq_thresh: :class:`int`
:param set_offset: Shall we update offsets for attached views?
:type set_offset: :class:`bool`
:param remove_empty: Shall we remove sequences with only gaps in cut aln?
:type remove_empty: :class:`bool`
:returns: Starting column (0-indexed), where cut region starts (w.r.t.
original aln). -1, if there is no region in the alignment with
at least the desired number of structures.
:rtype: :class:`int`
.. function:: CreateDistanceMap(aln)
Create distance map from a multiple sequence alignment.
The algorithm requires that the sequence alignment consists of at least two
sequences. The sequence at index 0 serves as a frame of reference. All the
other sequences must have an attached view and a properly set sequence offset
(see :meth:`~ost.seq.AlignmentHandle.SetSequenceOffset`).
For each of the attached views, the C-alpha distance pairs are extracted and
mapped onto the corresponding C-alpha distances in the reference sequence.
:param aln: Multiple sequence alignment.
:type aln: :class:`~ost.seq.AlignmentHandle`
:returns: Distance map.
:rtype: :class:`DistanceMap`
:raises: Exception if *aln* has less than 2 sequences or any sequence (apart
from index 0) is lacking an attached view.
.. function:: CreateVarianceMap(d_map, sigma=25)
:returns: Variance measure for each entry in *d_map*.
:rtype: :class:`VarianceMap`
:param d_map: Distance map as created with :func:`CreateDistanceMap`.
:type d_map: :class:`DistanceMap`
:param sigma: Used for weighting of variance measure
(see :meth:`Distances.GetWeightedStdDev`)
:type sigma: :class:`float`
:raises: Exception if *d_map* has no entries.
.. function:: CreateDist2Mean(d_map)
:returns: Distances to mean for each structure in *d_map*.
Structures are in the same order as passed when creating *d_map*.
:rtype: :class:`Dist2Mean`
:param d_map: Distance map as created with :func:`CreateDistanceMap`.
:type d_map: :class:`DistanceMap`
:raises: Exception if *d_map* has no entries.
.. function:: CreateMeanlDDTHA(d_map)
:returns: lDDT calculation based on CA carbons of the structures with lddt
distance threshold of 15 Angstrom and distance difference thresholds
of [0.5, 1.0, 2.0, 4.0]. The reported values for a certain structure
are the mean per-residue lDDT values given all other structures as
reference. Structures are in the same order as passed when creating
*d_map*.
:rtype: :class:`MeanlDDT`
:param d_map: Distance map as created with :func:`CreateDistanceMap`.
:type d_map: :class:`DistanceMap`
:raises: Exception if *d_map* has no entries.
.. class:: Distances
Container used by :class:`DistanceMap` to store a pair wise distance for each
structure. Each structure is identified by its index in the originally used
alignment (see :func:`CreateDistanceMap`).
.. method:: GetDataSize()
:returns: Number of pairwise distances.
:rtype: :class:`int`
.. method:: GetAverage()
:returns: Average of all distances.
:rtype: :class:`float`
:raises: Exception if there are no distances.
.. method:: GetMin()
GetMax()
:returns: Minimal/maximal distance.
:rtype: :class:`tuple` (distance (:class:`float`), index (:class:`int`))
:raises: Exception if there are no distances.
.. method:: GetDataElement(index)
:returns: Element at given *index*.
:rtype: :class:`tuple` (distance (:class:`float`), index (:class:`int`))
:param index: Index within list of distances (must be < :meth:`GetDataSize`).
:type index: :class:`int`
:raises: Exception if there are no distances or *index* out of bounds.
.. method:: GetStdDev()
:returns: Standard deviation of all distances.
:rtype: :class:`float`
:raises: Exception if there are no distances.
.. method:: GetWeightedStdDev(sigma)
:returns: Standard deviation of all distances multiplied by
exp( :meth:`GetAverage` / (-2*sigma) ).
:rtype: :class:`float`
:param sigma: Defines weight.
:type sigma: :class:`float`
:raises: Exception if there are no distances.
.. method:: GetNormStdDev()
:returns: Standard deviation of all distances divided by :meth:`GetAverage`.
:rtype: :class:`float`
:raises: Exception if there are no distances.
.. class:: DistanceMap
Container returned by :func:`CreateDistanceMap`.
Essentially a symmetric :meth:`GetSize` x :meth:`GetSize` matrix containing
up to :meth:`GetNumStructures` distances (list stored as :class:`Distances`).
Indexing of residues starts at 0 and corresponds to the positions in the
originally used alignment (see :func:`CreateDistanceMap`).
.. method:: GetDistances(i_res1, i_res2)
:returns: List of distances for given pair of residue indices.
:rtype: :class:`Distances`
:param i_res1: Index of residue.
:type i_res1: :class:`int`
:param i_res2: Index of residue.
:type i_res2: :class:`int`
.. method:: GetSize()
:returns: Number of residues in map.
:rtype: :class:`int`
.. method:: GetNumStructures()
:returns: Number of structures originally used when creating the map
(see :func:`CreateDistanceMap`).
:rtype: :class:`int`
.. class:: VarianceMap
Container returned by :func:`CreateVarianceMap`.
Like :class:`DistanceMap`, it is a symmetric :meth:`GetSize` x :meth:`GetSize`
matrix containing variance measures.
Indexing of residues is as in :class:`DistanceMap`.
.. method:: Get(i_res1, i_res2)
:returns: Variance measure for given pair of residue indices.
:rtype: :class:`float`
:param i_res1: Index of residue.
:type i_res1: :class:`int`
:param i_res2: Index of residue.
:type i_res2: :class:`int`
.. method:: GetSize()
:returns: Number of residues in map.
:rtype: :class:`int`
.. method:: Min()
Max()
:returns: Minimal/maximal variance in the map.
:rtype: :class:`float`
.. method:: ExportDat(file_name)
ExportCsv(file_name)
ExportJson(file_name)
Write all variance measures into a file. The possible formats are:
- "dat" file: a list of "*i_res1+1* *i_res2+1* variance" lines
- "csv" file: a list of ";" separated variances (one line for each *i_res1*)
- "json" file: a JSON formatted file (see :meth:`GetJsonString`)
:param file_name: Path to file to be created.
:type file_name: :class:`str`
:raises: Exception if the file cannot be opened for writing.
.. method:: GetJsonString()
:returns: A JSON formatted list of :meth:`GetSize` lists with
:meth:`GetSize` variances
:rtype: :class:`str`
.. method:: GetData()
Gets all the data in this map at once. Note that this is much faster (10x
speedup observed) than parsing :meth:`GetJsonString` or using :meth:`Get`
on each element.
:returns: A list of :meth:`GetSize` lists with :meth:`GetSize` variances.
:rtype: :class:`list` of :class:`list` of :class:`float`
.. method:: GetSubData(num_res_to_avg)
Gets subset of data in this map by averaging neighboring values for
*num_res_to_avg* residues.
:returns: A list of ceil(:meth:`GetSize`/*num_res_to_avg*) lists with
ceil(:meth:`GetSize`/*num_res_to_avg*) variances.
:rtype: :class:`list` of :class:`list` of :class:`float`
.. class:: Dist2Mean
Container returned by :func:`CreateDist2Mean`.
Stores distances to mean for :meth:`GetNumResidues` residues of
:meth:`GetNumStructures` structures.
Indexing of residues is as in :class:`DistanceMap`.
Indexing of structures goes from 0 to :meth:`GetNumStructures` - 1 and is in
the same order as the structures in the originally used alignment.
.. method:: Get(i_res, i_str)
:returns: Distance to mean for given residue and structure indices.
:rtype: :class:`float`
:param i_res: Index of residue.
:type i_res: :class:`int`
:param i_str: Index of structure.
:type i_str: :class:`int`
.. method:: GetNumResidues()
:returns: Number of residues.
:rtype: :class:`int`
.. method:: GetNumStructures()
:returns: Number of structures.
:rtype: :class:`int`
.. method:: ExportDat(file_name)
ExportCsv(file_name)
ExportJson(file_name)
Write all distance measures into a file. The possible formats are:
- "dat" file: a list of "*i_res+1* distances" lines (distances are space
separated)
- "csv" file: a list of ";" separated distances (one line for each *i_res*)
- "json" file: a JSON formatted file (see :meth:`GetJsonString`)
:param file_name: Path to file to be created.
:type file_name: :class:`str`
:raises: Exception if the file cannot be opened for writing.
.. method:: GetJsonString()
:returns: A JSON formatted list of :meth:`GetNumResidues` lists with
:meth:`GetNumStructures` distances.
:rtype: :class:`str`
.. method:: GetData()
Gets all the data in this map at once. Note that this is much faster (10x
speedup observed) than parsing :meth:`GetJsonString` or using :meth:`Get`
on each element.
:returns: A list of :meth:`GetNumResidues` lists with
:meth:`GetNumStructures` distances.
:rtype: :class:`list` of :class:`list` of :class:`float`
.. method:: GetSubData(num_res_to_avg)
Gets subset of data in this map by averaging neighboring values for
*num_res_to_avg* residues.
:returns: A list of ceil(:meth:`GetNumResidues`/*num_res_to_avg*) lists with
:meth:`GetNumStructures` distances.
:rtype: :class:`list` of :class:`list` of :class:`float`
.. class:: MeanlDDT
Container returned by :func:`CreateMeanlDDTHA`.
Stores mean lDDT values for :meth:`GetNumResidues` residues of
:meth:`GetNumStructures` structures.
Has the exact same functionality and behaviour as :class:`Dist2Mean`
HMM Algorithms
--------------------------------------------------------------------------------
Openstructure implements basic HMM-related functionality that aims at
calculating an HMM-HMM alignment score as described in
Soding, Bioinformatics (2005) 21(7), 951-60. This is the score which is
optimized in the Viterbi algorithm of the hhalign tool.
As a prerequisite, OpenStructure also implements adding pseudo counts to
:class:`ost.seq.ProfileHandle` in order to avoid zero probabilities for
unobserved transitions/emissions. Given these requirements, all functions
in this section require HMM related data (transition probabilities, neff values,
etc.) to be set, which is the case if you load a file in hhm format.
.. method:: HMMScore(profile_0, profile_1, aln, s_0_idx, s_1_idx, \
match_score_offset=-0.03,correl_score_weight=0.1, \
del_start_penalty_factor=0.6, \
del_extend_penalty_factor=0.6, \
ins_start_penalty_factor=0.6, \
ins_extend_penalty_factor=0.6)
Scores an HMM-HMM alignment given in *aln* between *profile_0* and
*profile_1*.
The score is described in Soding, Bioinformatics (2005) 21(7), 951-60 and
consists of three components:
* sum of column alignment scores of all aligned columns, the
*match_score_offset* is applied to each of those scores
* sum of transition probability scores, the prefactor of those scores can
be controlled with penalty factors (*del_start_penalty_factor* etc.)
* correlation score which rewards conserved columns occuring in clusters,
*correl_score_weight* controls its contribution to the total score
You have to make sure that proper pseudo counts are already assigned before
calling this function. You can find a usage example in this documentation.
This score is not necessarily consistent with the output generated with
hhalign, i.e. you take the hhalign output alignment and directly feed it
into this function with the same profiles and expect an equal score.
The reason is that by default, hhalign performs a re-alignment step but the
output score actually relates to the initial alignment coming from the
Viterbi alignment. To get consistent results, run hhalign with the
-norealign flag.
:param profile_0: First profile to be scored
:param profile_1: Second profile to be scored
:param aln: Alignment connecting the two profiles
:param s_0_idx: Idx of sequence in *aln* that describes *profile_0*
:param s_1_idx: Idx of sequence in *aln* that describes *profile_1*
:param match_score_offset: Offset which is applied to each column alignment
score
:param correl_score_weight: Prefactor to control contribution of correlation
score to total score
:param del_start_penalty_factor: Factor which is applied for each transition
score starting a deletion
:param del_extend_penalty_factor: Factor which is applied for each transition
score extending a deletion
:param ins_start_penalty_factor: Factor which is applied for each transition
score starting an insertion
:param ins_extend_penalty_factor: Factor which is applied for each transition
score extending an insertion
:type profile_0: :class:`ost.seq.ProfileHandle`
:type profile_1: :class:`ost.seq.ProfileHandle`
:type aln: :class:`ost.seq.AlignmentHandle`
:type s_0_idx: :class:`int`
:type s_1_idx: :class:`int`
:type match_score_offset: :class:`float`
:type correl_score_weight: :class:`float`
:type del_start_penalty_factor: :class:`float`
:type del_extend_penalty_factor: :class:`float`
:type ins_start_penalty_factor: :class:`float`
:type ins_extend_penalty_factor: :class:`float`
:raises: Exception if profiles don't have HMM information assigned or
specified sequences in *aln* don't match with profile SEQRES.
Potentially set sequence offsets are taken into account.
**Example with pseudo count assignment:**
.. code-block:: python
from ost import io, seq
prof_query = io.LoadSequenceProfile("query.hhm")
prof_tpl = io.LoadSequenceProfile("tpl.hhm")
aln = io.LoadAlignment("aln.fasta")
# assign pseudo counts to transition probabilities
seq.alg.AddTransitionPseudoCounts(prof_query)
seq.alg.AddTransitionPseudoCounts(prof_tpl)
# hhblits/hhalign 3 assign different pseudo counts to
# query and template. The reason is computational efficiency.
# The more expensive Angermueller et al. pseudo counts
# are assigned to the query.
path_to_crf = "/path/to/hh-suite/data/context_data.crf"
lib = seq.alg.ContextProfileDB.FromCRF(path_to_crf)
seq.alg.AddAAPseudoCounts(prof_query, lib)
# templates are assigned the computationally cheaper pseudo
# counts derived from a Gonnet substitution matrix
seq.alg.AddAAPseudoCounts(prof_tpl)
# assign null model pseudo counts
# this should be done AFTER you assigned pseudo counts to emission
# probabilities as this affects the result
seq.alg.AddNullPseudoCounts(prof_query)
seq.alg.AddNullPseudoCounts(prof_tpl)
print("score:", seq.alg.HMMScore(prof_query, prof_tpl, aln, 0, 1))
.. method:: AddNullPseudoCounts(profile)
Adds pseudo counts to null model in *profile* as implemented in hhalign.
Conceptually we're mixing the original null model with the frequencies
observed in the columns of *profile*. The weight of the original null model
depends on the neff value of *profile*. This function should be called
AFTER you already assigned pseudo counts to the emission probabilities
as this affects the result.
:param profile: Profile to add pseudo counts
:type profile: :class:`ost.seq.ProfileHandle`
:raises: Exception if profile doesn't have HMM information assigned
.. method:: AddTransitionPseudoCounts(profile, gapb=1.0, gapd=0.15, gape=1.0)
Adds pseudo counts to the transition probabilities in *profile* as implemented
in hhalign with equivalent parameter naming and default parameterization.
The original transition probabilities are mixed with prior
probabilities that are controlled by *gapd* and *gape*. Priors:
* priorM2I = priorM2D = *gapd* * 0.0286
* priorM2M = 1.0 - priorM2D - priorM2I
* priorI2I = priorD2D = 1.0 * *gape* / (gape - 1.0 + 1.0/0.75)
* priorI2M = priorD2M = 1.0 - priorI2I
Transition probabilities of column i starting from a match state are
then estimated with pM2X = (neff[i] - 1) * pM2X + *gape* * priorM2X.
Starting from an insertion/deletion state we have
pI2X = neff_ins[i] * pI2X + *gape* * priorI2X. In the end, all
probabilities are normalized such that (pM2M, pM2I, pM2D) sum up to one,
(pI2M, pI2I) sum up to one and (pD2I, pD2D) sum up to one.
:param profile: Profile to add pseudo counts
:type profile: :class:`ost.seq.ProfileHandle`
:raises: Exception if profile doesn't have HMM information assigned
.. method:: AddAAPseudoCounts(profile, a=1.0, b=1.5, c=1.0)
Adds pseudo counts to the emission probabilities in *profile* by mixing in
probabilities from the Gonnet matrix as implemented in hhalign with equivalent
parameter naming and default parameterization. We only implement the
diversity-dependent mode for the mixing factor tau (default in hhalign), which
for column *i* depends on *neff[i]* , *a* , *b* and *c* .
:param profile: Profile to add pseudo counts
:type profile: :class:`ost.seq.ProfileHandle`
:raises: Exception if profile doesn't have HMM information assigned
.. class:: ContextProfileDB
Database that contains context profiles which will be used to add pseudo
counts as described by
Angermueller et al., Bioinformatics (2012) 28, 3240-3247.
.. method:: FromCRF(filename)
Static load function which reads a crf file provided in an hh-suite
installation. Default location: "path/to/hhsuite/data/context_data.crf"
:param filename: Filename of CRF file
:type filename: :class:`str`
.. method:: Save(filename)
Saves database in OST-internal binary format which can be loaded faster than
a crf file.
:param filename: Filename to save db
:type filename: :class:`str`
.. method:: Load(filename)
Static load function that loads database in OST-internal binary format.
:param filename: Filename of db
:type filename: :class:`str`
.. method:: AddAAPseudoCounts(profile, db, a=0.9, b=4.0, c=1.0)
Adds pseudo counts to the emission probabilities in *profile* by utilizing
context profiles as described in
Angermueller et al., Bioinformatics (2012) 28, 3240-3247.
We only implement the
diversity-dependent mode for the mixing factor tau (default in hhalign), which
for column *i* depends on *neff[i]* , *a* , *b* and *c* .
:param profile: Profile to add pseudo counts
:type profile: :class:`ost.seq.ProfileHandle`
:param db: Database of context profiles
:type db: :class:`ContextProfileDB`
:raises: Exception if profile doesn't have HMM information assigned
AAIndex annotations
-------------------
.. autoclass:: ost.seq.alg.aaindex.AAIndex
:members:
:special-members: __getitem__
The annotations/scores can either refer to single amino acids or represent
pairwise values. The two types are:
.. autoclass:: ost.seq.alg.aaindex.AnnoType
:members:
:undoc-members:
The actual data of an entry in the aaindex database is stored in a
:class:`aaindex.AAIndexData` object:
.. autoclass:: ost.seq.alg.aaindex.AAIndexData
:members: