Stereochemical Divergence of Polyprenol Phosphate Glycosyltransferases

In the three domains of life, lipid-linked glycans contribute to various cellular processes ranging from protein glycosylation to glycosylphosphatidylinositol anchor biosynthesis to peptidoglycan assembly. In generating many of these glycoconjugates, phosphorylated polyprenol-based lipids are charged with single sugars by polyprenol phosphate glycosyltransferases. The resultant substrates serve as glycosyltransferase donors, complementing the more common nucleoside diphosphate sugars. It had been accepted that these polyprenol phosphate glycosyltransferases acted similarly, given their considerable sequence homology. Recent findings, however, suggest that matters may not be so simple. In this Opinion we propose that the stereochemistry of sugar addition by polyprenol phosphate glycosyltransferases is not conserved across evolution, even though the GT-A fold that characterizes such enzymes is omnipresent. Keywords: dolichol phosphate, dolichol phosphate glucose synthase, dolichol phosphate mannose synthase, polyprenol phosphate, protein glycosylation, stereochemistryIsrael Science Foundation (Grant 109/16)National Institutes of Health (U.S.) (Grant GM-039334)Israel Science Foundation (Grant 2253/15)National Natural Science Foundation (China) (Grant 2193/16)German-Israeli Foundation for Scientific Research and Development (Grant I-1290-416.13/2015