title: Functional role of positively selected amino acid substitutions in mammalian rhodopsin evolution.
abstract: Visual rhodopsins are membrane proteins that function as light photoreceptors in the vertebrate retina. Specific amino acids have been positively selected in visual pigments during mammal evolution, which, as products of adaptive selection, would be at the base of important functional innovations. We have analyzed the top candidates for positive selection at the specific amino acids and the corresponding reverse changes (F13M, Q225R and A346S) in order to unravel the structural and functional consequences of these important sites in rhodopsin evolution. We have constructed, expressed and immunopurified the corresponding mutated pigments and analyzed their molecular phenotypes. We find that position 13 is very important for the folding of the receptor and also for proper protein glycosylation. Position 225 appears to be important for the function of the protein affecting the G-protein activation process, and position 346 would also regulate functionality of the receptor by enhancing G-protein activation and presumably affecting protein phosphorylation by rhodopsin kinase. Our results represent a link between the evolutionary analysis, which pinpoints the specific amino acid positions in the adaptive process, and the structural and functional analysis, closer to the phenotype, making biochemical sense of specific selected genetic sequences in rhodopsin evolution.
authors: Grup de Biotecnologia Molecular i Industrial, Centre de Biotecnologia Molecular, Departament d'Enginyeria Química, Universitat Politècnica de Catalunya, Edifici Gaia, Rambla de Sant Nebridi 22, 08222 Terrassa, Catalonia, Spain.
authors: Miguel A
authors: MA
authors: Fernández-Sampedro
authors: IBE - Institute of Evolutionary Biology (CSIC-Universitat Pompeu Fabra), CEXS-UPF-PRBB, Barcelona, Catalonia, Spain.
authors: Brandon M
authors: BM
authors: Invergo
authors: Grup de Biotecnologia Molecular i Industrial, Centre de Biotecnologia Molecular, Departament d'Enginyeria Química, Universitat Politècnica de Catalunya, Edifici Gaia, Rambla de Sant Nebridi 22, 08222 Terrassa, Catalonia, Spain.
authors: Eva
authors: E
authors: Ramon
authors: IBE - Institute of Evolutionary Biology (CSIC-Universitat Pompeu Fabra), CEXS-UPF-PRBB, Barcelona, Catalonia, Spain.
authors: Jaume
authors: J
authors: Bertranpetit
authors: Grup de Biotecnologia Molecular i Industrial, Centre de Biotecnologia Molecular, Departament d'Enginyeria Química, Universitat Politècnica de Catalunya, Edifici Gaia, Rambla de Sant Nebridi 22, 08222 Terrassa, Catalonia, Spain.
authors: Pere
authors: P
authors: Garriga
mesh_terms: D000222:Adaptation, Physiological; D000409:Alanine / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001120:Arginine / Q000737:chemistry / Q000378:metabolism; D005075:Biological Evolution; D019556:COS Cells; D002522:Chlorocebus aethiops; D051606:G-Protein-Coupled Receptor Kinase 1 / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D005973:Glutamine / Q000737:chemistry / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D008322:Mammals / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D008715:Methionine / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D010649:Phenylalanine / Q000737:chemistry / Q000378:metabolism; D010766:Phosphorylation; D010802:Phylogeny; D017510:Protein Folding; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012243:Rhodopsin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D012641:Selection, Genetic; D012694:Serine / Q000737:chemistry / Q000378:metabolism
chemical_list: D011994:Recombinant Proteins; D005973:Glutamine; D012694:Serine; D010649:Phenylalanine; D012243:Rhodopsin; D001120:Arginine; D008715:Methionine; D051606:G-Protein-Coupled Receptor Kinase 1; D000409:Alanine