Dolichol, yeast

Characteristically, the a-isoprene unit is saturated, unlike bacterial undecaprenol, in which it is unsaturated, The dolichol mono- and di-phosphoric esters function as glycosylated intermediates2 in the synthesis of glycoproteins, keratan sulfate, cellulose, and yeast mannan, and that is why they are discussed here. 

Although it could be established that saturation of the a-isoprene unit of polyprenol phosphate is important for these compounds to act as effective acceptors of glycosyl moieties in eukaryotic cells, little chain-length specificity was observed in such studies.39-41 This observation found support in the result that the same set of prenylogs occurs in total-yeast dolichol and in dolichol diphosphate-linked 2-acetamido-2-deoxy-D-glucose synthesized in vitro with yeast-cell homogenates.42 As already noted by Chojnacki and coworkers,40 dur-... 

The enzymes catalyzing these reactions are membrane-bound, and are stimulated by exogenous dolichol phosphate. It has been suggested, and now shown43 (at least in the formation of GlcNAc-PP-Dol by enzymes from yeast), that Dol-P stimulates the incorporation of sugar residues into the lipid intermediates because it serves as a substrate. 

R Mazhari-Tabrizi, V Eckert, M Blank, R Muller, D Mumberg, M Funk, RT Schwarz. Cloning and functional expression of glycosyltransferases from parasitic protozoans by heterologous complementation in yeast the dolichol phosphate mannose synthase from Trypanosoma brucei. Biochem J 316 853-858, 1996. 

J Kato, S Fujisaki, K Nakajima, Y Nishimura, M Sato, A Nakano. The Escherichia coli homologue of yeast RER2, a key enzyme of dolichol synthesis is essential for carrier lipid formation in bacterial cell wall synthesis. J Bacteriol 181 2733-2738, 1999. 

Orlean, P., Albright, C., and Robbins, P. W. (1988). Cloning and sequencing of the yeast gene for dolichol phosphate mannose synthase, an essential protein./. Biol. Chem. 263,17499-17507. 

Sato, M., Sato, K., Nishikawa, S., Hirata, A., Kato, J., and Nakano, A. (1999). The yeast RER2 gene, identified by endoplasmic reticulum protein localization mutations, encodes aVprenyltransferase, a key enzyme in dolichol synthesis. Mol. Cell Biol. 19, 471-483. 

Dolichol-P-mannose is the mannose donor for all three mannosylation steps, whereas phosphatidylethanolamine contributes the phosphoethanolamine residues. Both these precursors are synthesized on the cytoplasmic face of the ER and must be flipped into the ER lumen to participate in GPI biosynthesis. The mannosyltransferases required for the assembly of the first, second, and third mannoses are PIG-M/PIG-X, PIG-V, and PIG-B (a fourth mannose residue that is essential for GPI assembly in yeast is transferred by the protein SMP3). Phosphoethanolamine side chains attached to the first, second, and third mannose residues are transferred by PIG-N, hGPI7/PIG-F, and PIG-O/PIG-F. Fully assembled GPI structures, or the GPI moiety in GPI-anchored proteins, are frequently subject to lipid re-modeling reactions in which fatty acids or the entire lipid structure is replaced with different fatty acids or lipids. 

Fernandez, F. Shridas, P. Jiang, S. Aebi, M. Waechter, C.J. Expression and characterization of a human cDNA that complements the temperature-sensitive defect in dolichol kinase activity in the yeast sec59-l mutant the enzymatic phosphorylation of dolichol and diacylglycerol are catalyzed by separate CTP-mediated kinase activities in Saccharomyces cerevisiae. Cly-cobiology, 12, 555-562 (2002)... 

The synthesis of large, branched, A/-glycosidically linked mannans appear to require the participation of dolichol. In yeasts the particular dolichols involved resemble those of plants, in that they are shorter by two to four isoprene units than are their counterparts in mammals. The a-isoprene group is saturated in animals, plants and fungi. 

Forms by Dictyostelium discoideum Journal of Biological Chemistryy 257, 9861-5 Park, J.T. Johnson, M.J. (1949) Accumulation of Labile Phosphate in Staphylococcus aureus Grown in the Presence of Penicillin , Journal of Biological Chemistry, 179, 585-92 Park, J.T. Strominger, J.L. (1957) Mode of Action of Penicillin , Science, 125, 99-101 Paro, A.J. (1976) Protein Glycosylation Through Dolichol Derivatives in Baker s Yeast , FEBS Letters, 71, 283-6... 

The biosynthesis of the mannan inner core involves dolichol pyrophosphate derivatives containing JV-acetyl glucosamine and several mannose residues [38]. The participation of the polyprenol (dolichol) in the biosynthesis of the mannan inner core in yeast is analagous to its role in animal tissues as a mechanism for the glycosylation of proteins. 

The scheme shown in Fig. 1 does not show all the reactions in which dolichol phosphate has been found to be involved. Thus yeast enzymes have been found to transfer mannose from dolichol-phosphate-mannose to serine or threonine residues (Babczinki ... 

Tanner, 1973). Furthermore addition of one or more mannoses from GDP-mannose would give rise to the formation of the short mannose chains found in yeast mannan. The other sugar protein linkage of mannan, which involves di N,acetylchitobiose is presumably formed through the dolichol containing intermediates. 

The participation of polyprenol sugar phosphates as intermediates in the biosynthesis of several types of complex carbohydrate has been clearly established in bacteria (for a review see ref. 11). Tanner in 1969< > presented the first evidence of the possible participation of lipid carriers in yeast. This was confirmed by us and the carrier was found to be a phosphodiester of mannose and an isoprenoid alcohol.Finally, Jung and Tanner purified a lipid which was able to accept mannose from GDP-mannose when added exogenously to a particulate preparation. This lipid was characterized as a dolichol phosphate. 

---