Molecular mechanism of protein synthesis

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We found that a high concentration (40-60%) of pyridine, an aromatic tertiary amine catalyst, is able to promote the translation on ribosomes without soluble protein factors of chemical energy sources. This novel translation system was called the pyridine system, which could produce oligophyenylalanine with chain lengths of up to decamer and polylysine with chain lengths of around 40mer, depending on the corresponding templates, poly (U) and poly (A), respectively. In poly (UC) -dependent oligo (serine-leucine) synthesis, oligopeptides with a serine and leucine alternate sequence were the main products. The template dependency is most prominent at 60% pyridine, but not observed at 40% or 50% pyridine. The optimal temperature range of the reaction was rather wide between 30 and 60ﾟC,which may reflect no requirement for temperature-sensitive soluble protein factors for the reaction. The ranges of the optimal concentrations of K^+ (200-500 mM) and Mg^<2+> (1-50 mM) in the pyridine system … More are also rather wide, quite different from those in the usual aqueous translation system.Current investigations have suggested that rRNAs play a central role in the ribosomal functions, although the conclusive evidence has not been provided ; some papers have reported that the eubacterial peptidyltransferation, the peptide-bond formation on the ribosomal large subunits, scarcely requires their proteins. Here we demonstrate that E.coli 23S rRNAs either extracted from ribosomes or synthesized in vitro are able to promote the peptide-bond formation (phenylalanylphenylalanine synthesis from phenylalanyl-tRNA^<Phe>) without template in the presence of 40% pyridine. The reaction required 23S rRNAs or the transcripts in the folded state, and was inhibited with chloramphenicol but not with cycloheximide as well as by site-directed digestion with RNase H of 23S rRNA hybridized with some complementary oligodeoxyribonucleotides. These results strongly suggest that 23S rRNA is directly involved in the peptide bond formation. Less