3AIC

Crystal Structure of Glucansucrase from Streptococcus mutans

Summary for 3AIC

• Entry DOI: 10.2210/pdb3aic/pdb
• Related: 3AIB 3AIE
• Related PRD ID: PRD_900007
• Descriptor: Glucosyltransferase-SI, 4,6-dideoxy-4-{[(1S,4R,5S,6S)-4,5,6-trihydroxy-3-(hydroxymethyl)cyclohex-2-en-1-yl]amino}-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose, CALCIUM ION, ... (5 entities in total)
• Functional Keywords: beta-alpha-barrels, transferase
• Biological source: Streptococcus mutans
• Cellular location: Secreted: P13470
• Total number of polymer chains: 8
• Total formula weight: 762689.74

Authors

Ito, K.,Ito, S.,Shimamura, T.,Iwata, S. (deposition date: 2010-05-12, release date: 2011-03-23, Last modification date: 2024-03-13)

Primary citation

Ito, K.,Ito, S.,Shimamura, T.,Weyand, S.,Kawarasaki, Y.,Misaka, T.,Abe, K.,Kobayashi, T.,Cameron, A.D.,Iwata, S.
Crystal structure of glucansucrase from the dental caries pathogen Streptococcus mutans.
J.Mol.Biol., 408:177-186, 2011

PubMed 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 α-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 α(1-3) glycosidic linkages or soluble glucan with α(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.

PubMed: 21354427
DOI: 10.1016/j.jmb.2011.02.028

Experimental method

X-RAY DIFFRACTION (3.11 Å)