Puromycin reaction of the A-site bound peptidyl-tRNA. |
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Authors: | Y P Semenkov T G Shapkina S V Kirillov |
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Institution: | BP Konstantinov Nuclear Physics Institute, Russian Academy of Sciences, Gatchina, Leningrad Region. |
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Abstract: | AcPhe2-tRNA(Phe) which appears in ribosomes after consecutive binding of AcPhe-tRNA(Phe) at the P sites and EF-Tu-directed binding of Phe-tRNA(Phe) at the A sites is able to react quantitatively with puromycin in the absence of EF-G. One could readily explain this fact to be the consequence of spontaneous translocation. However, a detailed study of kinetics of puromycin reaction carried out with the use of viomycin (inhibitor of translocation) and the P-site test revealed that, apart from spontaneous translocation, this peptidyl-tRNA could react with puromycin being located at the A site. This leads to the conclusion that the transpeptidation reaction triggers conformational changes in the A-site ribosomal complex bringing the 3'-end of a newly synthesized peptidyl-tRNA nearer to the peptidyl site of peptidyltransferase center. This is detected functionally as a highly pronounced ability of such a peptidyl-tRNA to react with puromycin. |
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