Sesión del 26 de Sept del 2014: Secuencias con composición inusual de aminoácidos

Seminario a cargo de Alejandra Zavala Castillo sobre complejidad en secuencia de proteínas:

Hola a tod@s:
Les anexo el artículo para el siguiente seminario sobre complejidad e información 🙂
Saludos!

Alejandra

El artículo está en esta Wootton-1994

Abstract

Segments of non-random amino acid composition, or
‘low-complexity’ regions, are very abundant in natural
protein sequences. They include sequences rich
in Ala, Gly, Pro, Gin, Ser, Thr, Asn, Glu, Asp, Arg,
His, Met, Lys, lie, Leu, Val, Phe residues, or combinations
of a few of these. Some segments are homopolymers
or nearly so, while others are irregular mosaics
of mixtures of two or a more residues, and some include
short-period regular repeats. They are strikingly
abundant in large nmltidomain polypeptides crucial
in morphogenesis, embryonic development, transcriptional
regulation, RNA processing, signal transduction
and both intracellular and extracellular structure and
integrity.
Several hundred publications from 1993 and the previous
few years (too many to list individually in this
review) have reported new amino acid sequences, deduced
from genomic or cDNA sequences, that contain
low-complexity regions or domains. Almost all authors
have used terms of surprise such as ‘unusual’, ‘unexpected’,
‘extraordinary’ and ‘remarkable’, perhaps reflecting
a belief that such segments are rare, which
they are not, or an expectation that normal proteins
should have locally complex, quasi-random compositions.
The current protein sequence and structure databases
[1-4] provide rich data for determining the actual abundance
and nature of low-complexity segments using
appropriate mathematical definitions of complexity.
The statistical improbability of several specific classes
of segments has been discussed for several years by
Karlin and Brendel [5-7], with emphasis on clusters of
charged amino acids. Recently, more general statistical
measures of compositional complexity have been applied
to both amino acid and nucleotide sequences and
to entire sequence databases [8″,9-11], and these form
the basis for the updated surveys reviewed here. Also
reviewed is recent evidence implicating some of the
low-complexity segments themselves in crucial molecular
interactions and biological functions of these proteins.
In only a few cases are relevant physicochemical
details beginning to emerge, and there are many
challenges for future research at the level of molecular
structure and dynamics.

Referencia
Wootton, J. C. (1994). Sequences with ‘unusual’amino acid compositions. Current Opinion in Structural Biology, 4(3), 413-421.

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