Comparative analysis of vertebrate <Emphasis Type="Italic">PEPT1</Emphasis> and <Emphasis Type="Italic">PEPT2</Emphasis> genes |
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Authors: | Minghui Wang Xiangzhe Zhang Hongbo Zhao Qishan Wang Yuchun Pan |
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Institution: | (1) School of Agriculture and Biology, Department of Animal Sciences, Shanghai Jiao Tong University, 200240 Shanghai, People’s Republic of China;(2) Shanghai Key Laboratory of Veterinary Biotechnology, 200240 Shanghai, China; |
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Abstract: | The plasma membrane transport proteins belong to SoLute Carrier 15 (SLC15) family and two members of this family have been
characterized extensively in higher vertebrates, namely PEPT1 and PEPT2. Despite many efforts have made to define a pharmacophore
model for efficient binding and transporting of substrates, there is not a comprehensive study performed to elucidate the
evolutionary mechanisms among the SLC15 family members and to statistically evaluate sequence conservation and functional
divergence between members. In this study, we compared and contrasted the rates and patterns of molecular evolution of 2 PEPT genes. Phylogenetic tree assembly with all available vertebrate PEPTs suggests that the PEPTs originated by duplications and diverged from a common protein at the base of the eukaryotic tree. Topological structure demonstrates
both members share the similar hydrophobic domains (TMDs), which have been constrained by purifying selection. Although both
genes show qualitatively similar patterns, their rates of evolution differ significantly due to an increased rate of synonymous
substitutions in the structural domains in one copy, suggesting substantial differences in functional constraint on each gene.
Site-specific profiles were established by posterior probability analysis revealing significantly divergent regions mainly
locate at the hydrophobic region between predicted transmembrane domains 9 and 10 of the proteins. Thus, these results provide
the evidence that several amino acid residues with reduced selective constraints are largely responsible for functional divergence
between the paralogous PEPTs. These findings may provide a starting point for further experimental verifications. |
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