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Crystal Structure of Glucansucrase from the Dental Caries Pathogen Streptococcus mutans

DOI: 10.1016/j.jmb.2011.02.028 DOI Help
PMID: 21354427 PMID Help

Authors: Keisuke Ito (The University of Tokyo) , Tatsuro Shimamura (Kyoto University) , Simone Weyand (Imperial College London) , Yasuaki Kawarasaki (University of Shizuoka) , Takumi Misaka (University of Tokyo) , Keiko Abe (University of Tokyo) , Takuya Kobayashi (Kyoto University) , Alexander D. Cameron (Imperial College London; Diamond Light Source) , So Iwata (Diamond Light Source; Japan Science and Technology Agency; Kyoto University Faculty of Medicine; Imperial College London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Molecular Biology

State: Published (Approved)
Published: February 2011
Diamond Proposal Number(s): 316

Abstract: Glucansucrase (GSase) from Streptococcus mutans is an essential agent in dental caries pathogenesis. Here, we report the crystal structure of S. mutans glycosyltransferase (GTF-SI), which synthesizes soluble and insoluble glucans and is a glycoside hydrolase (GH) family 70 GSase in the free enzyme form and in complex with acarbose and maltose. Resolution of the GTF-SI structure confirmed that the domain order of GTF-SI is circularly permuted as compared to that of GH family 13 ?-amylases. As a result, domains A, B and IV of GTF-SI are each composed of two separate polypeptide chains. Structural comparison of GTF-SI and amylosucrase, which is closely related to GH family 13 amylases, indicated that the two enzymes share a similar transglycosylation mechanism via a glycosyl-enzyme intermediate in subsite ? 1. On the other hand, novel structural features were revealed in subsites + 1 and + 2 of GTF-SI. Trp517 provided the platform for glycosyl acceptor binding, while Tyr430, Asn481 and Ser589, which are conserved in family 70 enzymes but not in family 13 enzymes, comprised subsite + 1. Based on the structure of GTF-SI and amino acid comparison of GTF-SI, GTF-I and GTF-S, Asp593 in GTF-SI appeared to be the most critical point for acceptor sugar orientation, influencing the transglycosylation specificity of GSases, that is, whether they produced insoluble glucan with ?(1–3) glycosidic linkages or soluble glucan with ?(1–6) linkages. The structural information derived from the current study should be extremely useful in the design of novel inhibitors that prevent the biofilm formation by GTF-SI.

Journal Keywords: Crystallography; X-Ray; Dental; Glucans; Glucosyltransferases; Glycosylation; Glycosyltransferases; Humans; Molecular; Protein; Sequence; Amino; Streptococcus mutans

Subject Areas: Biology and Bio-materials

Instruments: I02-Macromolecular Crystallography

Added On: 29/03/2011 11:32

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