NATURAL CYCLOHEXIMIDE RESISTANCE IN YEAST - THE ROLE OF RIBOSOMAL-PROTEIN L41

The yeast Kluyveromyces lactis is resistant to high concentrations (1 mg/ml) of the antibiotic cycloheximide. Using in vitro translation studies it was confirmed that this extreme resistance is a property of ribosomes. The resistance determinant from K. lactis was cloned into Saccharomyces cerevisiae. Nucleotide sequence analysis of the determinant demonstrated that resistance was conferred by the K. lactis ribosomal protein L41. K. lactis was shown to contain only one copy of the gene that encodes this protein and the gene was located to chromosome III. In contrast. S. cerevisiae was found to contain multiple copies of the gene for the corresponding ribosomal protein L41 which mapped to two of the three chromosomes V, XIV and VIII. Since the cycloheximide-resistance gene of K. lactis causes essentially complete protection against inhibition by the drug it is likely to be particularly useful as a selective marker in eukaryotic gene transfer studies.