Codon-dependent tRNA fluctuations monitored with fluorescence polarization.
During protein synthesis dictated by the codon sequence of messenger RNA, the ribosome selects aminoacyl-tRNA (aa-tRNA) with high accuracy, the exact mechanism of which remains elusive. By using a single-molecule fluorescence resonance energy transfer method coupled with fluorescence emission anisotropy, we provide evidence of random thermal motion of tRNAs within the ribosome in nanosecond timescale that we refer to as fluctuations. Our results indicate that cognate aa-tRNA fluctuates less frequently than near-cognate. This is counterintuitive because cognate aa-tRNA is expected to fluctuate more frequently to reach the ribosomal A-site faster than near-cognate. In addition, cognate aa-tRNA occupies the same position in the ribosome as near-cognate. These results argue for a mechanism which guides cognate aa-tRNA more accurately toward the A-site as compared to near-cognate. We suggest that a basis for this mechanism is the induced fit of the 30S subunit upon cognate aa-tRNA binding. Our single-molecule fluorescence resonance energy transfer time traces also point to a mechanistic model for GTP hydrolysis on elongation factor Tu mediated by aa-tRNA.
Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania, USA.
Padmaja P
PP
Mishra
Mohd Tanvir
MT
Qureshi
Wenhui
W
Ren
Tae-Hee
TH
Lee
D016880:Anisotropy; D001483:Base Sequence; D003062:Codon / Q000378:metabolism*; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation; D005454:Fluorescence Polarization / Q000379:methods*; D031541:Fluorescence Resonance Energy Transfer; D008969:Molecular Sequence Data; D009038:Motion; D010444:Peptide Elongation Factor Tu / Q000378:metabolism; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D015203:Reproducibility of Results; D012270:Ribosomes / Q000378:metabolism; D013997:Time Factors
D003062:Codon; D012346:RNA, Transfer, Amino Acyl; D004247:DNA; D010444:Peptide Elongation Factor Tu