Protein synthesis takes place on a mRNA programmed ribosome during the elongation phase of translation. Aminoacyl-tRNA is delivered to the aminoacyl site of the ribosome as a ternary complex with EF-Tu and GTP. Correct pairing of the mRNA codon and the tRNA anticodon stimulates conformational events which ultimately facilities the delivery of the amino acyl moiety into the peptidyltransferase center of the large subunit. This selection process can be biochemically distinguished into two steps: the first is known as initial selection which precedes GTP hydrolysis while the second step is known as proofreading and occurs subsequent to GTP hydrolysis.
We have developed a single molecule assay to probe these processes in explicit kinetic detail. This system provides the resolution necessary to measure three distinct states of the aa-tRNA selection process: codon recognition (FRET 0.2), GTPase activated state (FRET 0.3), and fully accommodated (FRET ~0.55). Our studies have revealed that the energy landscape of aa-tRNA selection favors aa-tRNA rejection accepting only 1 in 3 cognate aa-tRNA selection attempts.
Conformational Sampling of Aminoacyl-tRNA during Selection on the Bacterial Ribosome. Geggier PE, Dave R, Feldman MB, Terry D, Altman RB, Blanchard SC; J MOL BIOL (2010) Vol. 399:576-595. PMID:20434456.
Accommodation of Aminoacyl-tRNA into the Ribosome Involves Reversible Excursions along Multiple Pathways. Whitford PC, Geggier P, Altman RB, Blanchard SC, Onuchic JN, Sanbonmatsu KY; RNA (2010) Vol. 16(6): 1196-204. PMID: 20427512.
The Role of Fluctuations in tRNA Selection by the Ribosome. Lee TH, Blanchard SC, Kim HD, Puglisi JD, Chu S. PNAS (2007) Vol. 104, No. 34 pp 13661-13665. PMID: 17699629.