Structure of the gene encoding β-1,3-glucanase B of Bacillus circulans WL-12

β-1,3-Glucanases B (GlcB) and C (GlcC) are the major β-1,3-glucanases of Bacillus circulans WL-12 detected in the culture supernatant grown in β-1,3-glucan-free medium. The gene ( glcB) encoding GlcB was cloned into Escherichia coli and its nucleotide sequence was determined. The open reading frame of the glcB gene encodes a polypeptide of 412 amino acid residues. The N-terminal amino acid sequences of GlcB and GlcC purified from B. circulans culture supernatant were determined to be identical to each other and to the deduced sequence downstream of Ala-29. The N-terminal amino acid sequence, isoelectric point and estimated size of the β-1,3-glucanase produced by E. coli cells carrying the cloned glcB gene agreed well with those of GlcB of B. circulans WL-12. The N-terminal to central region of GlcB exhibited high sequence similarity to β-1,3-glucanases of alkalophilic Bacillus AG-430, GlcA1 of B. circulans WL-12 and the 87 kDa β-1,3-glucanase H of B. circulans IAM1165. The C-terminal region of GlcB exhibited sequence similarity to the C-terminal regions of XlnA of Streptomyces lividans, β-1,3-glucanases of Oerskovia xanthineolytica and Arthrobacter sp. YCWD3, and yeast lytic protease I of Rarobacter faecitabidus. Biochemical and sequence data strongly suggested that GlcC detected in the culture supernatant of B. circulans WL-12 corresponded to the catalytic domain of GlcB generated by loss of a C-terminal region of GlcB.