tRNA binding sites of ribosomes from Escherichia coli. 1984

R Lill, and J M Robertson, and W Wintermeyer

70S tight-couple ribosomes from Escherichia coli were studied with respect to activity and number of tRNA binding sites. The nitrocellulose filtration and puromycin assays were used both in a direct manner and in the form of a competition binding assay, the latter allowing an unambiguous determination of the fraction of ribosomes being active in tRNA binding. It was found that, in the presence of poly(U), the active ribosomes bound two molecules of N-AcPhe-tRNAPhe, one in the P and the other in the A site, at Mg2+ concentrations between 6 and 20 mM. A third binding site in addition to P and A sites was observed for deacylated tRNAPhe. At Mg2+ concentrations of 10 mM and below, the occupancy of the additional site was very low. Dissociation of tRNA from this site was found to be rather fast, as compared to both P and A sites. These results suggest that the additional site during translocation functions as an exit site, to which deacylated tRNA is transiently bound before leaving the ribosome. Since tRNA binding to this site did not require the presence of poly(U), a function of exit site bound tRNA in the fixation of the mRNA appears unlikely. Both the affinity and stability of binding to the additional site were found lower for the heterologous tRNAPhe from yeast as compared to the homologous one. This difference possibly indicates some specificity of the E. coli ribosome for tRNAs from the same organism.

UI MeSH Term Description Entries
D011072 Poly U A group of uridine ribonucleotides in which the phosphate residues of each uridine ribonucleotide act as bridges in forming diester linkages between the ribose moieties. Polyuridylic Acids,Uracil Polynucleotides,Poly(rU),Acids, Polyuridylic,Polynucleotides, Uracil
D004926 Escherichia coli A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc. Alkalescens-Dispar Group,Bacillus coli,Bacterium coli,Bacterium coli commune,Diffusely Adherent Escherichia coli,E coli,EAggEC,Enteroaggregative Escherichia coli,Enterococcus coli,Diffusely Adherent E. coli,Enteroaggregative E. coli,Enteroinvasive E. coli,Enteroinvasive Escherichia coli
D001665 Binding Sites The parts of a macromolecule that directly participate in its specific combination with another molecule. Combining Site,Binding Site,Combining Sites,Site, Binding,Site, Combining,Sites, Binding,Sites, Combining
D012270 Ribosomes Multicomponent ribonucleoprotein structures found in the CYTOPLASM of all cells, and in MITOCHONDRIA, and PLASTIDS. They function in PROTEIN BIOSYNTHESIS via GENETIC TRANSLATION. Ribosome
D012329 RNA, Bacterial Ribonucleic acid in bacteria having regulatory and catalytic roles as well as involvement in protein synthesis. Bacterial RNA
D012343 RNA, Transfer The small RNA molecules, 73-80 nucleotides long, that function during translation (TRANSLATION, GENETIC) to align AMINO ACIDS at the RIBOSOMES in a sequence determined by the mRNA (RNA, MESSENGER). There are about 30 different transfer RNAs. Each recognizes a specific CODON set on the mRNA through its own ANTICODON and as aminoacyl tRNAs (RNA, TRANSFER, AMINO ACYL), each carries a specific amino acid to the ribosome to add to the elongating peptide chains. Suppressor Transfer RNA,Transfer RNA,tRNA,RNA, Transfer, Suppressor,Transfer RNA, Suppressor,RNA, Suppressor Transfer
D012346 RNA, Transfer, Amino Acyl Intermediates in protein biosynthesis. The compounds are formed from amino acids, ATP and transfer RNA, a reaction catalyzed by aminoacyl tRNA synthetase. They are key compounds in the genetic translation process. Amino Acyl tRNA,Transfer RNA, Amino Acyl,tRNA-Amino Acyl,Amino Acyl T RNA,Acyl tRNA, Amino,Acyl, tRNA-Amino,tRNA Amino Acyl,tRNA, Amino Acyl

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