Intrinsically unstructured proteins evolve by repeat expansion.

TitleIntrinsically unstructured proteins evolve by repeat expansion.
Publication TypeJournal Article
Year of Publication2003
AuthorsTompa, P.
Date Published2003 Sep
KeywordsAlgorithms, Animals, Databases as Topic, Evolution, Molecular, Humans, Muscle Proteins, Polymorphism, Genetic, Proline, Protein Conformation, Protein Kinases, Protein Structure, Tertiary, Repetitive Sequences, Nucleic Acid, RNA Polymerase II, Structure-Activity Relationship, Trinucleotide Repeat Expansion

The proportion of the genome encoding intrinsically unstructured proteins increases with the complexity of organisms, which demands specific mechanism(s) for generating novel genetic material of this sort. Here it is suggested that one such mechanism is the expansion of internal repeat regions, i.e., coding micro- and minisatellites. An analysis of 126 known unstructured sequences shows the preponderance of repeats: the percentage of proteins with tandemly repeated short segments is much higher in this class (39%) than earlier reported for all Swiss-Prot (14%), yeast (18%) or human (28%) proteins. Furthermore, prime examples, such as salivary proline-rich proteins, titin, eukaryotic RNA polymerase II, the prion protein and several others, demonstrate that the repetitive segments carry fundamental function in these proteins. In addition, their repeat numbers show functionally significant interspecies variation and polymorphism, which underlines that these regions have been shaped by intense evolutionary activity. In all, the major point of this paper is that the genetic instability of repetitive regions combined with the structurally and functionally permissive nature of unstructured proteins has powered the extension and possible functional expansion of this newly recognized protein class.

Alternate JournalBioessays
PubMed ID12938174