| Tyrosinase, widely presented in various organisms, is a copper-containing enzyme that is involved mainly in the biosynthesis of melanin. Bioinformatics method was used to investigate the sequence features and evolutionary pattern of vertebrate TYR genes and to construct three dimensional structures of representative proteins. Phylogenetic analysis indicated that gene tree of vertebrate TYR proteins was highly consistent with species tree. Gene structure analysis showed that 5 exons were shared by most vertebrate TYR genes, DrTYR and OlTYR genes had 6 exons, and SsTYR gene had 9 exons. Analysis of protein sequence demonstrated that the common TYROSINASE domain was shared by vertebrate TYR proteins. In addition, different TYR proteins from distinct species had conserved motif organizations, but Motif 13 is specific to mammal TYR proteins. Selection pressure analysis was performed on the vertebrate TYR proteins using sitemodel and branch-site model. No amino acid sites were under positive selection via site model. However, three branches under positive selection were identified by branch-site model. Accordingly, 26 positively selected sites were identified from the ancestral branch of horse and pig. 27 positively selected sites were found from the pig branch. Only one positively selected site was identified from the ancestral branch of chicken and Zebra finch. These positively selected sites were distributed on different primary and secondary structures of TYR proteins, but were intensively distributed on the same area of three dimensional structures, suggesting that these sites were closely coupled to specific functions. |
