title: Amino acid sequence coevolution in the insect bursicon ligand-receptor system.
abstract: The pattern of amino acid residue replacement in the components of the bursicon signaling system (involving the BURSα/BURSβ heterodimer and its receptor BURSrec) was reconstructed across a phylogeny of 17 insect species, in order to test for the co-occurrence of replacements at sets of individual sites. Sets of three or more branches with perfectly concordant changes occurred to a greater extent than expected by chance, given the observed level of amino acid change. The latter sites (SPC sites) were found to have distinctive characteristics: (1) the mean number of changes was significantly lower at SPC sites than that at other sites with multiple changes; (2) SPC sites had a significantly greater tendency toward parallel amino acid changes than other sites with multiple changes, but no greater tendency toward convergent changes; and (3) parallel changes tended to involve relatively similar amino acids, as indicated by relatively low mean chemical distances. The results implicated functional constraint, permitting only a limited subset of amino acids in a given site, as a major factor in causing both parallel amino acid replacement and coordinated amino acid changes in different sites of the same protein and of interacting proteins in this system.
authors.affiliation: Department of Biological Sciences, University of South Carolina, Columbia, SC 29205, USA. austin@biol.sc.edu
authors.forename: Austin L
authors.initials: AL
authors.lastname: Hughes
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003198:Computer Simulation; D019143:Evolution, Molecular; D019476:Insect Proteins / Q000235:genetics*; D007313:Insecta / Q000235:genetics*; D007447:Invertebrate Hormones / Q000235:genetics*; D010802:Phylogeny; D017434:Protein Structure, Tertiary / Q000235:genetics; D043562:Receptors, G-Protein-Coupled / Q000235:genetics*; D017422:Sequence Analysis, DNA
chemical_list: D019476:Insect Proteins; D007447:Invertebrate Hormones; D043562:Receptors, G-Protein-Coupled; C002295:bursicon