Mutations in ribosomal protein L10e confer resistance to the fungal-specific eukaryotic elongation factor 2 inhibitor sordarin

The natural product sordarin, a tetracyclic diterpene glycoside, selectivel y inhibits fungal protein synthesis by impairing the function of eukaryotic elongation factor 2 (eEF2). Sordarin and its derivatives bind to the eEF2- ribosome-nucleotide complex in sensitive fungi, stabilizing the post-transl ocational GDP form. We have previously described a class of Saccharomyces c erevisiae mutants that exhibit resistance to varying levels of sordarin and have identified amino acid substitutions in yeast eEF2 that confer sordari n resistance. We now report on It second class of sordarin-resistant mutant s. Biochemical and molecular genetic analysis of these mutants demonstrates that sordarin resistance is dependent on the essential large ribosomal sub unit protein L10e in S. cerevisiae. Five unique L10e alleles were character ized and sequenced, and several nucleotide changes that differ from the wil d-type sequence were identified. Changes that result in the resistance phen otype map to 4 amino acid substitutions and 1 amino acid deletion clustered in a conserved 10-amino acid region of L10e. Like the previously identifie d eEF2 mutations, the mutant ribosomes show reduced sordarin conferred stab ilization of the eEF2-nucleotide-ribosome complex. To our know ledge, this report provides the first description of ribosomal protein mutations affect ing translocation. These results and our previous observations with eEF2 su ggest a functional linkage between L10e and eEF2.