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Eukaryotic Cell, August 2008, p. 1344-1351, Vol. 7, No. 8
1535-9778/08/$08.00+0     doi:10.1128/EC.00061-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Dolichyl-Phosphate-Glucose Is Used To Make O-Glycans on Glycoproteins of Trichomonas vaginalis ^,

Kariona A. Grabiska,¹ Sudip K. Ghosh,^1,2 Ziqiang Guan,³ Jike Cui,¹ Christian R. H. Raetz,³ Phillips W. Robbins,¹ and John Samuelson^1*

Department of Molecular and Cell Biology, Boston University Goldman School of Dental Medicine, Boston, Massachusetts 02118,¹ Department of Biotechnology, Indian Institute of Technology-Kharagpur, Kharagpur 721302, India,² Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710³

Received 15 February 2008/ Accepted 2 May 2008

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.

Published ahead of print on 13 June 2008.

Supplemental material for this article may be found at http://ec.asm.org/.