Fatty acylation of yeast glycoproteins proceeds independently of N-linked glycosylation.

The relationship between protein glycosylation and fatty acylation of glycoproteins was studied in the wild-type and asparagine-linked glycosylation-deficient mutants (alg1 and alg2) of Saccharomyces cerevisiae. At the non-permissive temperature (37 degrees C), both mutant cells exhibited increased incorporation of [3H]palmitate into five polypeptides based on SDS-PAGE. In contrast, the wild-type yeast cells contained [3H]palmitate-labeled polypeptides of higher molecular weights, which were converted to the bands seen in the mutant cells upon treatment of the cell extract with endoglycosidase H prior to SDS-PAGE. In addition, labeling of the wild-type yeast cells with [3H]palmitate in the presence of tunicamycin revealed the incorporation of [3H]palmitate into the same five bands as found in the alg1 and alg2 mutants at the non-permissive temperature without tunicamycin. These results indicate that fatty acylation of glycoproteins proceeds independently of protein N-glycosylation in yeast cells.