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Titolo:
THE ALLOSTERIC 3-SITE MODEL OF ELONGATION CANNOT BE CONFIRMED IN A WELL-DEFINED RIBOSOME SYSTEM FROM ESCHERICHIA-COLI
Autore:
SEMENKOV YP; RODNINA MV; WINTERMEYER W;
Indirizzi:
UNIV WITTEN HERDECKE,INST MOL BIOL D-58448 WITTEN GERMANY UNIV WITTEN HERDECKE,INST MOL BIOL D-58448 WITTEN GERMANY RUSSIAN ACAD SCI,ST PETERSBURG NUCL PHYS INST GATCHINA 188350 RUSSIA
Titolo Testata:
Proceedings of the National Academy of Sciences of the United Statesof America
fascicolo: 22, volume: 93, anno: 1996,
pagine: 12183 - 12188
SICI:
0027-8424(1996)93:22<12183:TA3MOE>2.0.ZU;2-E
Fonte:
ISI
Lingua:
ENG
Soggetto:
TRANSFER-RNA-BINDING; CODON-ANTICODON INTERACTION; DEACYLATED TRANSFER-RNA; AMINOACYL-TRANSFER-RNA; EXIT SITE; 3-SITE MODEL; MESSENGER-RNA; STEADY-STATE; FACTOR TU; CYCLE;
Keywords:
PROTEIN SYNTHESIS; EXIT SITE; TRANSLOCATION; ELONGATION FACTOR G;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
37
Recensione:
Indirizzi per estratti:
Citazione:
Y.P. Semenkov et al., "THE ALLOSTERIC 3-SITE MODEL OF ELONGATION CANNOT BE CONFIRMED IN A WELL-DEFINED RIBOSOME SYSTEM FROM ESCHERICHIA-COLI", Proceedings of the National Academy of Sciences of the United Statesof America, 93(22), 1996, pp. 12183-12188

Abstract

For the functional role of the ribosomal tRNA exit (E) site, two different models have been proposed, It has been suggested that transient E-site binding of the tRNA leaving the peptidyl (P) site promotes elongation factor G (EP-G)-dependent translocation by lowering the energetic barrier of tRNA release [Lill, R., Robertson, J. M. & Wintermeyer, W. (1989) EMBO J. 8, 3933-3938], The alternative ''allosteric three-site model'' [Nierhaus, K. H. (1990) Biochemistry 29, 4997-5008] features stable, codon-dependent tRNA binding to the E site and postulates a coupling between E and aminoacyl (A) sites that regulates the tRNA binding affinity of the two sites in an anticooperative manner. Extendingour testing of the two conflicting models, we have performed translocation experiments with fully active ribosomes programmed with heteropolymeric mRNA. The results confirm that the deacylated tRNA released from the P site is bound to the E site in a kinetically labile fashion, and that the affinity of binding, i.e., the occupancy of the E site, is increased by Mg2+ Or polyamines. At conditions of high E-site occupancy in the posttranslocation complex, filling the E site with aminoacyl-tRNA had no influence on the E site, i.e., there was no detectable anticooperative coupling between the two sites, provided that second-round translocation was avoided by removing EF-G. On the basis of these results, which are entirely consistent with our previous results, we consider the allosteric three-site model of elongation untenable, Rather, as proposed earlier, the E site-bound state of the leaving tRNA is a transient intermediate and, as such, is a mechanistic feature of theclassic two-state model of the elongating ribosome.

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Documento generato il 01/04/20 alle ore 23:09:44