THE YEAST MIC2 MUTANT IS DEFECTIVE IN THE FORMATION OF MANNOSYL-DIINOSITOLPHOSPHORYLCERAMIDE

The mic2 mutation dominantly blocks formation of mannosyl-diinositolph osphorylceramide, the most abundant sphingolipid of the yeast, Sacchar omyces cerevisiae, Interestingly, lack of mannosyl-diinositolphosphory lceramide is not lethal but is compensated for by increased amounts of inositolphosphorylceramide and mannosyl-inositolphosphorylceramide in the plasma membrane and Golgi of the mutant. The level of negatively charged phospholipids in the plasma membrane of the mid strain is mark edly reduced; the sterol composition is not altered, In spite of drama tic changes of its lipid composition the mutant grows like wild type o n complex and minimal media, under osmotic stress conditions, at low p H, and in the presence of high ionic strength. While sensitivity to se veral drugs is not altered, the mic2 mutant strain becomes resistant t o the polyene antibiotic nystatin. (C) 1997 Federation of European Bio chemical Societies.