Characterization of a Haloarchaeal GH Family 18 Chitinase with Additional Acidic Amino Acids on Its Protein Surface

Abstract

A chitinase (ChiN1) from Halobacterium salinarum NRC-1 belongs to the glycoside hydrolase family 18. According to the three-dimensional structure model of ChiN1, Asn239 and Gln242 on a small helix between Phe237 and Arg247 were targeted for mutagenesis. Mutants N239D (Asn239 was replaced by Asp) and Q242E (Gln242 was replaced by Glu) were expressed in Haloarcula japonica and then characterized. Characterization of the mutants revealed that halotolerancy could be improved by introducing an acidic amino acid on the surface of ChiN1.