Improving the acidic stability of a methyl parathion hydrolase by changing basic residues to acidic residues
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The acidic stability of a methyl parathion hydrolase (Ochr-MPH) was improved by selectively changing basic amino acids to acidic ones. Mutation sites were selected based on the position-specific amino acid replacement probabilities (more than or equal to 0.2) and the entropy of each site (more than or equal to 0.8). Three mutants (K208E, K277D, and K208E/K277D) were more stable than the wild-type (WT). Their half-lives at pH 5.0 were 64, 68, 65 min, respectively, whereas that of WT was 39 min. The acidic stability of proteins may therefore be improved by changing selected basic amino acid residues to acidic ones.
KeywordsAcidic amino acid Acidic stability Methyl parathion hydrolase Site-directed mutagenesis
This work was supported by grants from the National Natural Science Foundation of China (Grant no. 30900839) and the National High Technology Research and Development Program of China (863 Program, 2007AA100605).
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