title: Crystal structure of glycoside hydrolase family 55 {beta}-1,3-glucanase from the basidiomycete Phanerochaete chrysosporium.
abstract: Glycoside hydrolase family 55 consists of beta-1,3-glucanases mainly from filamentous fungi. A beta-1,3-glucanase (Lam55A) from the Basidiomycete Phanerochaete chrysosporium hydrolyzes beta-1,3-glucans in the exo-mode with inversion of anomeric configuration and produces gentiobiose in addition to glucose from beta-1,3/1,6-glucans. Here we report the crystal structure of Lam55A, establishing the three-dimensional structure of a member of glycoside hydrolase 55 for the first time. Lam55A has two beta-helical domains in a single polypeptide chain. These two domains are separated by a long linker region but are positioned side by side, and the overall structure resembles a rib cage. In the complex, a gluconolactone molecule is bound at the bottom of a pocket between the two beta-helical domains. Based on the position of the gluconolactone molecule, Glu-633 appears to be the catalytic acid, whereas the catalytic base residue could not be identified. The substrate binding pocket appears to be able to accept a gentiobiose unit near the cleavage site, and a long cleft runs from the pocket, in accordance with the activity of this enzyme toward various beta-1,3-glucan oligosaccharides. In conclusion, we provide important features of the substrate-binding site at the interface of the two beta-helical domains, demonstrating an unexpected variety of carbohydrate binding modes.
authors.affiliation: Departments of Biomaterials Sciences and Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Ishida
authors.forename: Shinya
authors.initials: S
authors.lastname: Fushinobu
authors.forename: Rie
authors.initials: R
authors.lastname: Kawai
authors.forename: Motomitsu
authors.initials: M
authors.lastname: Kitaoka
authors.forename: Kiyohiko
authors.initials: K
authors.lastname: Igarashi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Samejima
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002384:Catalysis; D018360:Crystallography, X-Ray; D043326:Glucan 1,3-beta-Glucosidase / Q000737:chemistry*; D006868:Hydrolysis; D007700:Kinetics; D008958:Models, Molecular; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D020075:Phanerochaete / Q000201:enzymology*; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D047071:beta-Glucans / Q000737:chemistry
chemical_list: D010455:Peptides; D047071:beta-Glucans; C033363:beta-1,3-glucan; D043326:Glucan 1,3-beta-Glucosidase