The contribution of DNA to translation errors induced by streptomycin in vitro.

Abstract

appropriate site and distort the structure of the mRNA.2 In this case, there is no necessary connection between the structure of the ribosome and the fidelity of translation in the absence of Sm. An alternative interpretation suggests that the structure of both the ribosome as well as the mRNA contributes to the specificity of translation and Sm causes errors by altering the structure of the sensitive ribosome.l In this case, the structure of the ribosome could influence the fidelity of translation even in the absence of Sm. If this were so, a genetic alteration of the ribosome might lead to translation errors in the absence of error-inducing antibiotics. This prediction led us to an analysis of streptomycin-dependent (SmD) ribosomes to determine whether the removal of Sm from the SmD system could lead to the production of translation errors. If this were observed, it should aid in establishing the structural contribution of the ribosomes to the fidelity of translation. However, the experiments with SmI) ribosomes met with an unexpected difficulty. Although it was possible to demonstrate Sm-dependent polyphenylalanine synthesis with a suitably purified in vitro system,3 it proved difficult to duplicate the original observations of Sm-induced translation errors with purified ribosomes and enzymes from the streptomycin-sensitive (SmS) bacteria. As a consequence of these difficulties, we have reinvestigated the in vitro effects of Sm on the fidelity of translation. The results of this study show that there are two different effects of Sm on the fidelity of poly U-directed polypeptide synthesis. First, there is an enhancement of leucine incorporation which is obtained with SmS,