Dolichyl-phosphate-glucose is used to make O-glycans on glycoproteins of Trichomonas vaginalis.
Trichomonas vaginalis, the protist that causes vaginal itching, has a huge genome with numerous gene duplications. Recently we found that Trichomonas has numerous genes encoding putative dolichyl-phosphate-glucose (Dol-P-Glc) synthases (encoded by ALG5 genes) despite the fact that Trichomonas lacks the glycosyltransferases (encoded by ALG6, ALG8, and ALG10 genes) that use Dol-P-Glc to glucosylate dolichyl-PP-linked glycans. In addition, Trichomonas does not have a canonical DPM1 gene, encoding a dolichyl-P-mannose (Dol-P-Man) synthase. Here we show Trichomonas membranes have roughly 300 times the Dol-P-Glc synthase activity of Saccharomyces cerevisiae membranes and about one-fifth the Dol-P-Man synthase activity of Saccharomyces membranes. Endogenous Dol-P-hexoses of Trichomonas are relatively abundant and contain 16 isoprene units. Five paralogous Trichomonas ALG5 gene products have Dol-P-Glc synthase activity when expressed as recombinant proteins, and these Trichomonas Alg5s correct a carboxypeptidase N glycosylation defect in a Saccharomyces alg5 mutant in vivo. A recombinant Trichomonas Dpm1, which is deeply divergent in its sequence, has Dol-P-Man synthase activity. When radiolabeled Dol-P-Glc is incubated with Trichomonas membranes, Glc is incorporated into reducing and nonreducing sugars of O-glycans of endogenous glycoproteins. To our knowledge, this is the first demonstration of Dol-P-Glc as a sugar donor for O-glycans on glycoproteins.
Department of Molecular and Cell Biology, Boston University Goldman School of Dental Medicine, 715 Albany Street, Evans 425, Boston, MA 02118, USA.
Kariona A
KA
Grabińska
Sudip K
SK
Ghosh
Ziqiang
Z
Guan
Jike
J
Cui
Christian R H
CR
Raetz
Phillips W
PW
Robbins
John
J
Samuelson
D000818:Animals; D004287:Dolichol Monophosphate Mannose / Q000378:metabolism; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism*; D007425:Intracellular Membranes / Q000378:metabolism; D008364:Mannosyltransferases / Q000378:metabolism; D011103:Polyisoprenyl Phosphate Monosaccharides / Q000378:metabolism*; D011134:Polysaccharides / Q000378:metabolism*; D014246:Trichomonas vaginalis / Q000235:genetics / Q000378:metabolism*
D006023:Glycoproteins; D011103:Polyisoprenyl Phosphate Monosaccharides; D011134:Polysaccharides; D004287:Dolichol Monophosphate Mannose; C002968:dolichol-D-glucosylmonophosphate; D005964:Glucosyltransferases; D008364:Mannosyltransferases; C022755:dolichyl-phosphate beta-D-mannosyltransferase