The major yeast wall glycoprotein (yeast mannan) is formed by mannose units linked to polypeptide backbones either through an, O-glycosydic bond to hydroxyl groups of serine and threonine or by an N-glycosydic bond conecting a residue of asparagine to a di-N-acetyl-chitobiose unit [1,2] . Dolichol-phosphate derivates especially dolicholphosphomannose (DPM) appear to play an important role [3,6,18] in the transfer of the first mannosyl residue to the hydroxyaminoacids. Guanosine-diphosphate-mannose (GDP-mannose) acts as the intermediate donor of mannose residues for further elongation of the oligosaccharides . Some of the enzymes involved in the synthesis of specific bonds have also been characterized [6,8,21]. Evidence that the initial glycosylation of glycoproteins in higher cells occurs at the level of nascent polypeptide has been reported by different groups [9-12] and studies carried out in our laboratory have shown that glycosylation of the mannoproteins of Saccharomyces cerevisiae wall is also initiated at the polysomal level . In this paper we present evidence that lysates of protoplasts incorporated mannose from either GDP-mannose or DPM in non-lipidic high molecular weight material. From the conditions of the reaction, the specific activities of the radioactive polysome and membrane fractions and the release of mannose by alkaline treatment it is suggested that DPM is the intermediate precursor for the mannosylation of hydroxy aminoacids at the polysomal level of the yeast wall glycoproteins.
Larriba, G., Elorza, M. V., Villanueva, J. R., & Sentandreu, R. (1976). Participation of dolichol phospho-mannose in the glycosylation of yeast wall manno-proteins at the polysomal level. FEBS Letters, 71(2), 316–320. https://doi.org/10.1016/0014-5793(76)80960-X