Template-free ribosomal synthesis of polypeptides from aminoacyl-tRNAs.
In the present paper it has been demonstrated that Escherichia coli ribosomes in the absence of messenger polynucleotides are capable of synthesizing some polypeptides from aminoacyl-tRNAs as substrates. EF-Tu induced binding of aminoacyl-tRNA, ribosomal peptidyl transferase and EF-G-promoted translocation are strictly required for this template-free elongation. Typical ribosomal inhibitors such as tetracycline, chloramphenicol, phenylboric acid, fusidic acid have been shown to inhibit the template-free synthesis of polypeptides. The synthesis requires GTP cleavage; a non-cleavable analog of GTP, guanyl-5'-yl methylenediphosphonate does not maintain the synthesis. Among sixteen different aminoacyl-tRNAs studied as substrates for the ribosomal template-free synthesis of polypeptides Lys-tRNA, Ser-tRNA, Thr-tRNA and Asp-tRNA were the best. Gly-tRNA, Glu-tRNA, Val-tRNA, Arg-tRNA, Ala-tRNA and Leu-tRNA as substrates gave relatively low levels of the polypeptide synthesis on nonprogrammed ribosomes. Pro-tRNA, Phe-tRNA, Asn-tRNA, Met-tRNA, Ile-tRNA and Gln-tRNA were practically inactive as substrates for the template-free elongation. No correlation has been found between the abilities of the aminoacyl-tRNAs to serve as substrates for the template-free elongation and their activities in template-free binding to ribosomes.
D004926:Escherichia coli; D010452:Peptide Biosynthesis; D010441:Peptide Chain Elongation, Translational; D012333:RNA, Messenger / Q000378:metabolism; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism*; D013698:Templates, Genetic
D012333:RNA, Messenger; D012346:RNA, Transfer, Amino Acyl