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"""Classes for providing extra information about an :class:`ihm.Entity`"""
import urllib.request
class Reference:
"""Base class for extra information about an :class:`ihm.Entity`.
This class is not used directly; instead, use a subclass such as
:class:`Sequence` or :class:`UniProtSequence`. These objects are
then typically passed to the :class:`ihm.Entity` constructor."""
pass
class Sequence(Reference):
"""Point to the sequence of an :class:`ihm.Entity` in a sequence database;
convenience subclasses are provided for common sequence databases such
as :class:`UniProtSequence`.
These objects are typically passed to the :class:`ihm.Entity`
constructor.
See also :attr:`alignments` to describe the correspondence between
the database and entity sequences.
:param str db_name: The name of the database.
:param str db_code: The name of the sequence in the database.
:param str accession: The database accession.
:param str sequence: The complete sequence, as a string of
one-letter codes.
:param str details: Longer text describing the sequence.
"""
def __init__(self, db_name, db_code, accession, sequence, details=None):
self.db_name, self.db_code = db_name, db_code
self.accession = accession
self.sequence, self.details = sequence, details
#: All alignments between the reference and entity sequences, as
#: :class:`Alignment` objects. If none are provided, a simple 1:1
#: alignment is assumed.
self.alignments = []
def _signature(self):
# Ignore "details"
return ((self.db_name, self.db_code, self.accession, self.sequence)
+ tuple(a._signature() for a in self.alignments))
def _get_alignments(self):
if self.alignments:
return self.alignments
elif not hasattr(self, '_default_alignment'):
self._default_alignment = Alignment()
return [self._default_alignment]
class UniProtSequence(Sequence):
"""Point to the sequence of an :class:`ihm.Entity` in UniProt.
These objects are typically passed to the :class:`ihm.Entity`
constructor.
:param str db_code: The UniProt name (e.g. NUP84_YEAST)
:param str accession: The UniProt accession (e.g. P52891)
See :class:`Sequence` for a description of the remaining parameters.
"""
_db_name = 'UNP'
def __init__(self, db_code, accession, sequence, details=None):
super().__init__(self._db_name, db_code, accession, sequence, details)
def __str__(self):
return "<ihm.reference.UniProtSequence(%r)>" % self.accession
@classmethod
def from_accession(cls, accession):
"""Create :class:`UniProtSequence` from just an accession.
This is done by querying the UniProt web API, so requires network
access.
:param str accession: The UniProt accession (e.g. P52891)
"""
# urlopen returns bytes
def decode(t):
return t.decode('ascii')
url = 'https://www.uniprot.org/uniprot/%s.fasta' % accession
with urllib.request.urlopen(url) as fh:
header = decode(fh.readline())
spl = header.split('|')
if len(spl) < 3 or spl[0] not in ('>sp', '>tr'):
raise ValueError("Cannot parse UniProt header %s" % header)
cd = spl[2].split(None, 1)
code = cd[0]
details = cd[1].rstrip('\r\n') if len(cd) > 1 else None
seq = decode(fh.read()).replace('\n', '')
return cls(code, accession, seq, details)
class Alignment:
"""A sequence range that aligns between the database and the entity.
This describes part of the sequence in the sequence database
(:class:`Sequence`) and in the :class:`ihm.Entity`. The two ranges
must be the same length and have the same primary sequence (any
differences must be described with :class:`SeqDif` objects).
:param int db_begin: The first residue in the database sequence
that is used (defaults to the entire sequence).
:param int db_end: The last residue in the database sequence
that is used (or None, the default, to use the entire sequence).
:param int entity_begin: The first residue in the :class:`~ihm.Entity`
sequence that is taken from the reference (defaults to the entire
entity sequence).
:param int entity_end: The last residue in the :class:`~ihm.Entity`
sequence that is taken from the reference (or None, the default,
to use the entire sequence).
:param seq_dif: Single-point mutations made to the sequence.
:type seq_dif: Sequence of :class:`SeqDif` objects.
"""
def __init__(self, db_begin=1, db_end=None, entity_begin=1,
entity_end=None, seq_dif=[]):
self.db_begin, self.db_end = db_begin, db_end
self.entity_begin, self.entity_end = entity_begin, entity_end
self.seq_dif = []
self.seq_dif.extend(seq_dif)
def _signature(self):
return ((self.db_begin, self.db_end, self.entity_begin,
self.entity_end)
+ tuple(s._signature() for s in self.seq_dif))
class SeqDif:
"""Annotate a sequence difference between a reference and entity sequence.
See :class:`Alignment`.
:param int seq_id: The residue index in the entity sequence.
:param db_monomer: The monomer type (as a :class:`~ihm.ChemComp` object)
in the reference sequence.
:type db_monomer: :class:`ihm.ChemComp`
:param monomer: The monomer type (as a :class:`~ihm.ChemComp` object)
in the entity sequence.
:type monomer: :class:`ihm.ChemComp`
:param str details: Descriptive text for the sequence difference.
"""
def __init__(self, seq_id, db_monomer, monomer, details=None):
self.seq_id, self.db_monomer = seq_id, db_monomer
self.monomer, self.details = monomer, details
def _signature(self):
# Don't ignore "details", as these distinguish insertions from
# deletions
return (self.seq_id, self.db_monomer, self.monomer, self.details)
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