Rates of amino acid evolution in the 26- and 28-kDa glutathione S-transferases of Schistosoma.
Statistical analysis of glutathione S-transferase (GST) sequences of Schistosoma mansoni, Schistosoma japonicum, and other animals revealed that, in comparison both to the related mammalian alpha GSTs and to Schistosoma 26-kDa GSTs, the 28-kDa GSTs of Schistosoma have evolved unusually rapidly at the amino acid level in the ordinarily conserved N-terminal portion of the molecule. Because this rapid rate of evolution is reflected at the amino acid level and at nonsynonymous nucleotide sites but not at synonymous nucleotide sites, it must be due to a relaxation of functional constraint on the N-terminal region of the Schistosoma 28-kDa GSTs rather than to a high mutation rate. By contrast, the 26-kDa GSTs of Schistosoma not only show a slower rate of amino acid evolution in the N-terminal portion than the 28-kDa GSTs but also have evolved more slowly in the C-terminal portion than have the related mammalian mu GSTs. The two 26-kDa GSTs of S. mansoni show particularly strong amino acid conservation between one another in the N-terminal region and a predominance of conservative amino acid replacements.
Hughes
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Department of Biology, Pennsylvania State University, University Park 16802.
D000595:Amino Acid Sequence; D000818:Animals; D005075:Biological Evolution; D017124:Conserved Sequence; D017238:Genes, Helminth / Q000235:genetics*; D005982:Glutathione Transferase / Q000235:genetics*; D015801:Helminth Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D012547:Schistosoma / Q000201:enzymology / Q000235:genetics*; D012641:Selection, Genetic; D017386:Sequence Homology, Amino Acid
D015801:Helminth Proteins; D005982:Glutathione Transferase