Proteolytic degradation of ribosomal proteins during isolation of ribosomes and ribosomal subunits from Tetrahymena.

A preparation procedure previously used to isolate active ribosomal subunits from an amicronucleate strain of Tetrahymena of undefined phenoset (T. "pyriformis" CGL) yields inactive subunits when applied to other amicronucleate or to micronucleate strains of this protozoa. Proteolytic degradation of a small number of ribosomal proteins during preparation of ribosomal subunits from these strains explains this results. If cell extraction and ribosome isolation are carried out in the presence of iodoacetamide, proteolytic activity is inhibited and active ribosomal subunits are obtained. Comparison of the protein complements of active ribosomal subunits prepared in the presence of iodoacetamide from three amicronucleate strains of Tetrahymena reveals small but significant differences.