SUMMARY PARAGRAPH for CWH41
During N-linked glycosylation of proteins, oligosaccharide chains are assembled on the carrier molecule dolichyl pyrophosphate in the following order: 2 molecules of N-acetylglucosamine (GlcNAc), 9 molecules of mannose, and 3 molecules of glucose. These 14-residue oligosaccharide cores are then transferred to asparagine residues on nascent polypeptide chains in the endoplasmic reticulum (ER). As proteins progress through the Golgi apparatus, the oligosaccharide cores are modified by trimming and extension to generate a diverse array of glycosylated proteins (reviewed in 5, 6).
CWH41, also known as GLS1, encodes glucosidase I (E.C. 18.104.22.168), an integral membrane protein of the ER (4) which removes the terminal glucose from core oligosaccharides immediately after they are transferred to proteins (7), thereby reversing the reaction catalyzed by Die2p. Although cwh41 mutants are deficient in trimming glucose from core oligosaccharides (3, 8), the downstream effect is usually not severe. Mutants grow, mate, and sporulate normally (4, 8), but have reduced levels of beta-1,6-glucan in the cell wall (4), causing hypersensitivity to the drug Calcofluor White (4, 1) and resistance to yeast K1 killer toxin (4, 1). Proteins with extraneous glucose moieties otherwise mature and are secreted normally (8), although there is a report of failure to degrade certain proteins in the ER (2). Deficiency of the human homolog, GCS1 (OMIM), causes the congenital disorder of glycosylation CDG-IIb (OMIM).
Last updated: 2005-07-06