Specificity of bacterial ribosomes and messenger ribonucleic acids in protein synthesis reactions in vitro

Abstract

Ribosomes from two Gram-negative bacteria translated f2 RNA, T4 early mRNA, mRNA from three Gran-negative bacteria, and mRNA from six Gram-positive bacteria; ribosomes from three Gram-positive bacteria translated mRNA from the Gram-positive strains, but did not translate the other mRNAs. Ribosomes from the Gram-negative bacterium Escherichia coli translated synthetic poly(U,G) but ribosomes from the Gram-positive bacterium Clostridium pasteurianum translated poly(U,G) very poorly, mRNA from Gram-negative bacteria was translated only in the presence of a high salt ribosomal wash containing initiation factors. mRNA from Gram-positive bacteria and synthetic poly(U,G) were translated much more efficiently when wash components were present, but were also translated to a small, but significant, extent in the absence of wash components. The translation specificity of each type of ribosome was independent of the source of ribosomal wash components. When the radioactively labeled products of in vitro protein synthesis were analyzed by sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis and autoradiography, it was found that each different bacterial and phage RNA preparation directed the synthesis of a unique set of polypeptide products of discrete sizes. Three different types of ribosomes were used to translate each of several Gram-positive bacterial messenger preparations; the overall patterns of products obtained with a given mRNA are similar, but some differences in the products formed or the relative amounts of the various products synthesized can be detected.