[Cloning and sequencing of chitinase gene from Bacillus thuringiensis subsp israelensis]

Chitin, a linear homopolymer of N-acetyl-D-glucosamine, is a common constituent of fungal cell walls, exoskeletons of insects, and shells of invertebrates. Thus, chitinase, a chitin hydrolytic enzyme, has become of interest for potential use as biopesticides for controlling insect pests. Using a pair of specific primers, chitinase gene (ichi) was amplified by touchdown PCR from Bacillus thuringiensis subsp israelensis chromosomal DNA, and then subcloned into pGEM-T easy vector. ichi sequence (GenBank Accession Number: AF526379) with a length of 2570 bp included an open reading frame (ORF) of 2067 bp, which contained 688 amino acids with Mr = 75.79 kDa and pI = 5.90. The amino acid sequence of ichi gene shows 97.24%, 97.18%, 97.63% and 63.07% identity to that of Bacillus cereus strain 28-9 chitinase CW, Bacillus cereus CH chitinase B, Bt subsp Mexican chitinase, and Bt subsp pakistani chitinase A71, respectively. It was demonstrated that Ichi contains a signal peptide (46 amino acid residues) and three functional domains: an N-terminal catalytic domain (105 amino acid residues), a fibronectin type III like domain (74 amino acid residues), and a C-terminal chitin-binding domain (40 amino acid residues).