title: Evolution of the complement system C3 gene in Antarctic teleosts.
abstract: Notothenioidei are typical Antarctic teleosts evolved to adapt to the very low temperatures of the Antarctic seas. Aim of the present paper is to investigate sequence and structure of C3, the third component of the complement system of the notothenioid Trematomus bernacchii and Chionodraco hamatus. We determined the complete nucleotide sequence of two C3 isoforms of T. bernacchii and a single C3 isoform of C. hamatus. These sequences were aligned against other homologous teleost sequences to check for the presence of diversifying selection. Evidence for positive selection was observed in the evolutionary lineage of Antarctic teleost C3 sequences, especially in that of C. hamatus, the most recently diverged species. Adaptive selection affected numerous amino acid positions including three residues located in the anaphylatoxin domain. In an attempt to evaluate the link between sequence variants and specific structural features, we constructed molecular models of Antarctic teleost C3s, of their proteolytic fragments C3b and C3a, and of the corresponding molecules of the phylogenetically related temperate species Epinephelus coioides, using human crystallographic structures as templates. Subsequently, we compared dynamic features of these models by molecular dynamics simulations and found that the Antarctic C3s models show higher flexibility, which likely allows for more pronounced movements of both the TED domain in C3b and the carboxyl-terminal region of C3a. As such dynamic features are associated to positively selected sites, it appears that Antarctic teleost C3 molecules positively evolved toward an increased flexibility, to cope with low kinetic energy levels of the Antarctic marine environment.
authors.affiliation: Department of Biology and Evolution of Marine Organisms, Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Napoli (SZN), Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Melillo
authors.affiliation: Institute of Protein Biochemistry, CNR, Via Pietro Castellino 111, 80131 Napoli, Italy.
authors.forename: Sonia
authors.initials: S
authors.lastname: Varriale
authors.affiliation: Institute of Protein Biochemistry, CNR, Via Pietro Castellino 111, 80131 Napoli, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Giacomelli
authors.affiliation: Department of Biology and Evolution of Marine Organisms, Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Napoli (SZN), Italy.
authors.forename: Lenina
authors.initials: L
authors.lastname: Natale
authors.affiliation: Department of Comparative Biomedicine and Food Science, University of Padua, Via Ugo Bassi 58/B, 35131 Padova, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Bargelloni
authors.affiliation: Institute of Protein Biochemistry, CNR, Via Pietro Castellino 111, 80131 Napoli, Italy.
authors.forename: Umberto
authors.initials: U
authors.lastname: Oreste
authors.affiliation: Department of Biology and Evolution of Marine Organisms, Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Napoli (SZN), Italy.
authors.forename: Maria Rosaria
authors.initials: MR
authors.lastname: Pinto
authors.affiliation: Institute of Protein Biochemistry, CNR, Via Pietro Castellino 111, 80131 Napoli, Italy. Electronic address: mr.coscia@ibp.cnr.it.
authors.forename: Maria Rosaria
authors.initials: MR
authors.lastname: Coscia
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics / Q000276:immunology; D000706:Anaphylatoxins / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D000818:Animals; D000864:Antarctic Regions; D001483:Base Sequence; D003080:Cold Temperature; D003176:Complement C3 / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D019143:Evolution, Molecular; D029941:Fish Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D015870:Gene Expression; D006801:Humans; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D010473:Perciformes / Q000145:classification / Q000235:genetics / Q000276:immunology*; D010802:Phylogeny; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D017434:Protein Structure, Tertiary; D059748:Proteolysis; D012641:Selection, Genetic; D016415:Sequence Alignment
chemical_list: D000706:Anaphylatoxins; D003176:Complement C3; D029941:Fish Proteins; D020033:Protein Isoforms
keywords: Anaphylatoxin; Antarctic teleost; Cold adaptation; Complement system component C3; Molecular flexibility; Positive evolution