SCHIZOSACCHAROMYCES-POMBE GLYCOSYLATION MUTANT WITH ALTERED CELL-SURFACE PROPERTIES

Mntagenesis of Schizosaccharomyces pombe cells yielded a strain that m ade reduced amounts of invertase. A comparison of the O- and N-linked carbohydrate chains of the wild-type and mutant glycoproteins revealed that a single type of alpha 1-->2-linked mannose was missing in the m utant. Analysis of the wild-type galactomannoprotein showed that it co ntained a heterogeneous small ''core'' oligosaccharide fraction linked to asparagine with sugar compositions that ranged from Man(9)(GlcNAc) (2)-to Gal(4)Man(10)(GlcNAc)(2-). The galactose units are in terminal positions of a Man(10)(GlcNAc)(2-) unit that is similar to the mannopr otein core of Saccharomyces cerevisiae. Attached to this core in a lar ger oligosaccharide fraction is an alpha 1-->6-Linked polymannose chai n that is substituted at position 2 with alpha-linked mannose and gala ctose. The O-linked sugars consist of mannose, alpha 1-->2-Linked mann osylmannose and alpha 1-->2-linked galactosylmannose, along with small amounts of tri- and tetrasaccharides. The glycosylation mutant lacks alpha 1-->2-linked mannose on both the O-linked chains and the outer c hain of the large N-Linked chains, suggesting that it may be defective in regulation of an (alpha 1,2-mannosyltransferase that adds mannose to glycoproteins in the Golgi.