THERMAL INSTABILITY OF TETRAHYMENA RIBOSOMES - EFFECTS ON PROTEIN SYNTHESIS

The thermal denaturation curves of ribosomes from two strains of Tetrahymena pyriformis and a wild strain of Escherichia coli have been compared. The Tetrahymena ribosomes show significant denaturation at temperatures close to each strain's maximum growth temperature; both are considerably less stable than those of the bacterium. The translational efficiency of each strain was measured by determining the ratio of amino acid incorporation under optimal growth conditions and at temperatures slightly above and below the temperature supporting a maximum growth rate. The same temperature levels which initiate in vitro ribosomal melting cause significant in vivo reductions in the efficiency of messenger translation. The loss in template efficiency does not appear to be associated with any qualitative impairment of the translation of individual messengers, since the size distribution on a molecular sieve (Sephadex G-200) is unchanged. © 1969.