1s4n
Crystal structure of yeast alpha1,2-mannosyltransferase Kre2p/Mnt1p
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OverviewOverview
Kre2p/Mnt1p is a Golgi alpha1,2-mannosyltransferase involved in the, biosynthesis of Saccharomyces cerevisiae cell wall glycoproteins. The, protein belongs to glycosyltransferase family 15, a member of which has, been implicated in virulence of Candida albicans. We present the 2.0 A, crystal structures of the catalytic domain of Kre2p/Mnt1p and its binary, and ternary complexes with GDP/Mn(2+) and GDP/Mn(2+)/acceptor, methyl-alpha-mannoside. The protein has a mixed alpha/beta fold similar to, the glycosyltransferase-A (GT-A) fold. Although the GDP-mannose donor was, used in the crystallization experiments and the GDP moiety is bound, tightly to the active site, the mannose is not visible in the electron, density. The manganese is coordinated by a modified DXD motif (EPD), with, only the first glutamate involved in a direct interaction. The position of, the donor mannose was modeled using the binary and ternary complexes of, other GT-A enzymes. The C1" of the modeled donor mannose is within, hydrogen-bonding distance of both the hydroxyl of Tyr(220) and the O2 of, the acceptor mannose. The O2 of the acceptor mannose is also within, hydrogen bond distance of the hydroxyl of Tyr(220). The structures, modeling, site-directed mutagenesis, and kinetic analysis suggest two, possible catalytic mechanisms. Either a double-displacement mechanism with, the hydroxyl of Tyr(220) as the potential nucleophile or alternatively, an, S(N)i-like mechanism with Tyr(220) positioning the substrates for, catalysis. The importance of Tyr(220) in both mechanisms is highlighted by, a 3000-fold reduction in k(cat) in the Y220F mutant.
About this StructureAbout this Structure
1S4N is a Single protein structure of sequence from Saccharomyces cerevisiae with CL and GOL as ligands. Active as Glycolipid 2-alpha-mannosyltransferase, with EC number 2.4.1.131 Full crystallographic information is available from OCA.
ReferenceReference
Structure of Kre2p/Mnt1p: a yeast alpha1,2-mannosyltransferase involved in mannoprotein biosynthesis., Lobsanov YD, Romero PA, Sleno B, Yu B, Yip P, Herscovics A, Howell PL, J Biol Chem. 2004 Apr 23;279(17):17921-31. Epub 2004 Jan 28. PMID:14752117
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