title: Inferring functional constraints and divergence in protein families using 3D mapping of phylogenetic information.
abstract: Comparative sequence analysis has been used to study specific questions about the structure and function of proteins for many years. Here we propose a knowledge-based framework in which the maximum likelihood rate of evolution is used to quantify the level of constraint on the identity of a site. We demonstrate that site-rate mapping on 3D structures using datasets of rhodopsin-like G-protein receptors and alpha- and beta-tubulins provides an excellent tool for pinpointing the functional features shared between orthologous and paralogous proteins. In addition, functional divergence within protein families can be inferred by examining the differences in the site rates, the differences in the chemical properties of the side chains or amino acid usage between aligned sites. Two novel analytical methods are introduced to characterize rate- independent functional divergence. These are tested using a dataset of two classes of HMG-CoA reductases for which only one class can perform both the forward and reverse reaction. We show that functionally divergent sites occur in a cluster of sites interacting with the catalytic residues and that this information should facilitate the design of experimental strategies to directly test functional properties of residues.
authors.affiliation: Canadian Institute for Advanced Research, Program in Evolutionary Biology, Genome Atlantic, Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS B3H 4H7, Canada. bongo@hades.biochem.dal.ca
authors.forename: Christian
authors.initials: C
authors.lastname: Blouin
authors.forename: Yan
authors.initials: Y
authors.lastname: Boucher
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Roger
mesh_terms: D000818:Animals; D019143:Evolution, Molecular; D019204:GTP-Binding Proteins / Q000378:metabolism; D014644:Genetic Variation; D006801:Humans; D006903:Hydroxymethylglutaryl CoA Reductases / Q000737:chemistry / Q000235:genetics; D010751:Phosphopyruvate Hydratase / Q000737:chemistry / Q000235:genetics; D010802:Phylogeny; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry / Q000235:genetics*; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012243:Rhodopsin / Q000737:chemistry / Q000235:genetics; D014404:Tubulin / Q000737:chemistry / Q000235:genetics
chemical_list: D011506:Proteins; D011956:Receptors, Cell Surface; D014404:Tubulin; D012243:Rhodopsin; D006903:Hydroxymethylglutaryl CoA Reductases; D019204:GTP-Binding Proteins; D010751:Phosphopyruvate Hydratase