Characterisation of the ribosomal proteins from Schizosaccharomyces pombe by two-dimensional polyacrylamide gel electrophoresis

Summary

The 80S ribosome of Schizosaccharomyces pombe contains 93 proteins as determined by twodimensional electrophoresis on polyacrylamide gels. Of these, 76 are basic and 17 are acidic at pH 8.7. 38 proteins could be assigned unambiguosly to the large sub-unit and 19 to the small.

67 proteins were extracted from the two-dimensional gels and their molecular weights determined by electrophoresis on calibrated SDS-gels. Values varied from 11,000 to 52,000 daltons, the number average being 25,000 daltons. Hence the total protein content of the 80S ribosome must be at least 1.67x10⁶ daltons.

Three drug resistant strains are known, cyh1, anil and tri5 (resistant to cycloheximide, anisomycin and trichodermin respectively), in which resistace is conferred by an altered ribosome, in each case by an altered 60S sub-unit. When 80S ribosomal protein patterns from these strains were compared with that of wild type, in only one case was a clear difference seen. This involved a large sub-unit, basic protein (designated number 66 on our classification) which, in the cyh1 strain, had a reduced mobility in the second dimension when compared to the wild type. The mutant form of protein 66 had a molecular weight of 25,000 daltons compared to the 22,000 of the wild type protein. Production of a larger protein by the mutant strain could either be due to a readthrough event or to an alteration in the specificity of a modifying or processing enzyme.