Solution Structure of the Chitin-binding Domain ofBacillus circulansWL-12 Chitinase A1
Journal of Biological Chemistry
The three-dimensional structure of the chitin-binding domain (ChBD) of chitinase A1 (ChiA1) from a Grampositive bacterium, Bacillus circulans WL-12, was determined by means of multidimensional heteronuclear NMR methods. ChiA1 is a glycosidase that hydrolyzes chitin and is composed of an N-terminal catalytic domain, two fibronectin type III-like domains, and C-terminal ChBD ChiA1 (45 residues, Ala 655 -Gln 699 ), which binds specifically to insoluble chitin. ChBD ChiA1 has a compact and globular
... ompact and globular structure with the topology of a twisted ␤-sandwich. This domain contains two antiparallel ␤-sheets, one composed of three strands and the other of two strands. The core region formed by the hydrophobic and aromatic residues makes the overall structure rigid and compact. The overall topology of ChBD ChiA1 is similar to that of the cellulose-binding domain (CBD) of Erwinia chrysanthemi endoglucanase Z (CBD EGZ ). However, ChBD ChiA1 lacks the three aromatic residues aligned linearly and exposed to the solvent, which probably interact with cellulose in CBDs. Therefore, the binding mechanism of a group of ChBDs including Ch-BD ChiA1 may be different from that proposed for CBDs.