title: Involvement of Gln679, in addition to Trp687, in chitin-binding activity of the chitin-binding domain of chitinase A1 from Bacillus circulans WL-12.
abstract: Chitinase A1 (ChiA1) from Bacillus circulans WL-12 comprises an N-terminal catalytic domain, two fibronectin type III domains, and a C-terminal chitin-binding domain (ChBD). The ChBD of ChiA1 (ChBDChiA1) belongs to carbohydrate-binding module (CBM) family 12 and specifically binds to insoluble or crystalline chitin. It has been suggested that tryptophan-687 (Trp687) is involved in the chitin-binding activity of this ChBD. Site-directed mutagenesis was used to identify additional amino acid residues required for chitin-binding activity of this domain. Furthermore, a total of 14 amino acid residues in ChBDChiA1 were carefully selected, and it was found that mutation of Gln679, which is not well-conserved in CBM family 12, significantly decreased the binding activity to colloidal chitin. A nuclear magnetic resonance study demonstrated that neither the Q679A nor the W687A mutation altered the overall structure of ChBDChiA1. Therefore, Gln679 was identified as a new residue that is involved in the chitin-binding activity of ChBDChiA1 in addition to Trp687. However, the mechanism of chitin binding by ChBD is still unknown.
authors.affiliation: Graduate School of Science and Technology, Niigata University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Hara
authors.forename: Hayuki
authors.initials: H
authors.lastname: Sugimoto
authors.forename: Michio
authors.initials: M
authors.lastname: Uemura
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Akagi
authors.forename: Kazushi
authors.initials: K
authors.lastname: Suzuki
authors.forename: Takahisa
authors.initials: T
authors.lastname: Ikegami
authors.forename: Takeshi
authors.initials: T
authors.lastname: Watanabe
mesh_terms: D019943:Amino Acid Substitution; D001407:Bacillus / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002686:Chitin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002688:Chitinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005973:Glutamine / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D014364:Tryptophan / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D005973:Glutamine; D002686:Chitin; D014364:Tryptophan; D002688:Chitinases
keywords: CBM family 12; chitin-binding domain; chitinase; site-directed mutagenesis; tryptophan