Yeast resistance to polyene antibiotics. VI. Isolation and biochemical analysis of strains of Saccharomyces cerevisiae yeasts with mutations in the 2 nystatin-resistance genes

The comparative analysis of sterol content in the yeast Saccharomyces cerevisiae strains singly or doubly defective in nystatin resistance genes was carried out. The strains with two mutations in NYS genes were shown to accumulate the sterol mixture, similar to that of the parental singly defective mutant. This type of gene interaction allows to define the main biochemical order of reaction in ergosterol synthesis: methylation in C24 (NYS1), delta 8----delta 7 isomerization (NYS2), C5 (6) and C22 (23) desaturation (NYS3 and NYSX).