Altered ribosomal proteins in mutants of the fungus Podospora anserina.

In the fungus Podospora anserina, a double mutant strain which combines two ribosomal mutations exhibits a marked sensitivity to NH4+ acetate. Mutations which suppress this phenotype were isolated. Two mutants were found to have an electrophoretically altered ribosomal protein. In one mutant, protein S15 from the small subunit has a reduced charge; in the other, the 60 S protein L16 is shorter than the homologous wild type protein. Both mutant and wild type proteins are present in heterokaryotic strains combining mutant and wild type nuclei. We therefore propose that the alteration of S15 and L16 results from mutations in the structural genes for these proteins.