5e9u
From Proteopedia
Crystal structure of GtfA/B complex bound to UDP and GlcNAc
Structural highlights
FunctionGTFA_STRGN Required for polymorphic O-glycosylation of GspB, a serine-rich repeat cell wall protein encoded upstream in the same operon. Catalyzes the first step in glycosylation by transferring N-acetylglucosamine from UDP-GlcNAc to serine residues in GspB. Part of the accessory SecA2/SecY2 system specifically required to export GspB. Upon coexpression in E.coli with GtfB glycosylates GspB constructs. Glycosylation probably occurs intracellularly (PubMed:15489421). Requires GtfB for glycosylation activity, it has no activity alone. Does not use UDP-glucose as substrate. Has a fast, probably processive glycosylation phase followed by a slower, non-processive phase. The enzyme probably modifies its tertiary conformation by opening and closing its intersubunit interfaces to accomodate the increasingly glycosylated substrate; protein substrate recognition is provided by GtfB (PubMed:26884191).[1] [2] Publication Abstract from PubMedO-glycosylation of Ser and Thr residues is an important process in all organisms, which is only poorly understood. Such modification is required for the export and function of adhesin proteins that mediate the attachment of pathogenic Gram-positive bacteria to host cells. Here, we have analyzed the mechanism by which the cytosolic O-glycosyltransferase GtfA/B of Streptococcus gordonii modifies the Ser/Thr-rich repeats of adhesin. The enzyme is a tetramer containing two molecules each of GtfA and GtfB. The two subunits have the same fold, but only GtfA contains an active site, whereas GtfB provides the primary binding site for adhesin. During a first phase of glycosylation, the conformation of GtfB is restrained by GtfA to bind substrate with unmodified Ser/Thr residues. In a slow second phase, GtfB recognizes residues that are already modified with N-acetylglucosamine, likely by converting into a relaxed conformation in which one interface with GtfA is broken. These results explain how the glycosyltransferase modifies a progressively changing substrate molecule. Mechanism of a cytosolic O-glycosyltransferase essential for the synthesis of a bacterial adhesion protein.,Chen Y, Seepersaud R, Bensing BA, Sullam PM, Rapoport TA Proc Natl Acad Sci U S A. 2016 Feb 16. pii: 201600494. PMID:26884191[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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