Molecular cloning and structural analysis of the gene encoding Bacillus cereus exochitinase Chi36

The chi36 gene encoding exochitinase Chi36 was cloned from a Bacillus cereu s 6E1 subgenomic library. The chi36 open reading frame is 1080 bp long enco ding a Chi36 precursor protein of 360 amino acids, consisting of a 27 amino acid N-terminal signal peptide and a 333 amino acid sequence found in the mature Chi36 protein of 36.346 kDa. Chi36 shows significant amino acid sequ ence similarity to many bacterial chitinases, but has highest similarity to B. circulans WL-12 chitinase D. Chi36 belongs to subfamily B of bacterial chitinases in family 18 of glycosyl hydrolases. Chi36 shows a simple and co mpact structural organization composed of an N-terminal signal peptide and a C-terminal (beta/(alpha)(8)-barrel catalytic domain (CaD). The Chi36 sign al peptide is recognized by Escherichia coli, allowing Chi36 secretion. Chi 36 is the first one-domain (CaD) bacterial chitinase cloned from B. cereus.