Double Stranded RNA in the Decoding of the mRNA by the Bacterial Ribosome
In the process of the decoding of the mRNA by the 70 S ribosome a hexanucleotide double stranded RNA is formed by the mRNA and the aminoacyl- and the peptidyl-tRNA. Both, in initiation or termination, however, only either the formylmethionylor the peptidyl-tRNA are present on the ribosome. According to a theory as outlined by Shine and Dalgarno the 3’ end of the 16 S RNA can form a short double strand with the mRNA. In order to prove these assumptions we prepared oligonucleotides containing the Shine-Dalgarno region and the initiation codon. These were examined in their capabilities to direct the binding of fMet-tRNA to the 30 S ribosome. The data indicate that the double strand formation between 16 S RNA and mRNA acts as a signal to stimulate the binding of the initiator-tRNA to the ribosomal subunit.
To elucidate details of the termination reaction the binding constants between the release factors and the codons UAA, UAG and UGA have been determined. Furthermore, we crosslinked the codons to the 70 S ribosomal termination complex. The nucleotides were crosslinked to both the proteins and the 16 S RNA. The data suggest that the termination codons interact with the 16 S RNA. A model, which explains the function of the 16 S RNA in initiation and elongation is proposed.
KeywordsRibosomal Subunit Termination Codon Release Factor Peptide Bond Formation Bacterial Ribosome
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