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Glycosylation defects corrected by the changes in GDPmannose level

100%

Kruszewska J., Janik A., Lenart U., Palamarczyk G.

Acta Biochimica Polonica

1999

tom 46

nr 2

GDPMan is a key substrate in glycoprotein formation. This is especially true for lower eukaryotes where, in addition to the involvement in N-glycan biosynthesis and GPI-anchor formation, GDPMan takes part in the process which is unique for yeast and fungi i.e. O-mannosylation. Several lines of evidence have been presented that the level of GDPMan affects the process occurring in the Golgi compartment i.e. the elongation of outer mannose chain of glycoproteins in Saccharomyces cerevisiae. Results from our laboratory indicate that the availability of GDPMan affects also the early steps of glycoprotein formation ascribed to the endoplasmic reticulum, i.e. assembly of the dolichol-linked oligosaccharide as well as mannosyl-phosphodolichol (MPD) formation. The biochemical basis of carbohydrate deficient glycoprotein syndrome, a severe neurological disorder related to the GDPMan deficiency, is also discussed.

Evidence for the involvement of a 66 kDa membrane protein in the synthesis of sterolglucoside in Saccharomyces cerevisiae

88%

Lenart U., Haplova J., Magdolen P., Farkas V., Palamarczyk G.

Acta Biochimica Polonica

1995

tom 42

nr 2

The membrane-bound sterolglucoside synthase from the yeast Saccharomyces cerevisiae has been solubilized by nonionic detergent, Nonidet P-40, Triton X-100, and partially purified by DEAE-cellulose column chromatography and ammonium sulfate fractionation. SDS/PAGE of the purified fraction revealed the presence of two protein bands of molecular mass 66 kDa and 54 kDa. In an attempt to identify further the polypeptide chain of sterolglucoside synthase, the partially purified enzyme was treated with [di-125I]-5-[3-(p-azidosalicylamide)]allyl-UDPglucose, a photoactive analogue of UDPglucose, which is a substrate for this enzyme. Upon photolysis the 12SI-labeled probe was shown to link covalently to the 66kDa protein. The photoinsertion was competed out by the presence of unlabeled UDPglucose thus suggesting that this protein contains substrate binding site for UDPglucose. Since photoinsertion of the probe to protein of 66 kDa correlates with the molecular mass of the protein visualized upon enzyme purification we postulate that the 66 kDa protein is involved in sterolglucoside synthesis in yeast.

Ograniczanie wyników

2 Acta Biochimica Polonica

2 Lenart U.

2 Palamarczyk G.

1 Farkas V.

1 Haplova J.

1 Janik A.

1 Kruszewska J.

1 Magdolen P.

1 1999

1 1995

Wyniki wyszukiwania

Glycosylation defects corrected by the changes in GDPmannose level

Evidence for the involvement of a 66 kDa membrane protein in the synthesis of sterolglucoside in Saccharomyces cerevisiae