Evidence for a conformational change in tRNAPhe upon aminoacylation.

Time-resolved fluorescence studies on the ternary complex formed between bacterial elongation factor Tu, guanosine 5'-triphosphate, and phenylalanyl-tRNAPhe

“…Structural differences between unacylated and aminoacylated tRNAs have also been investigated by using spin-label probes covalently attached to s4U8. An initial report of aminoacylation-dependent conformational changes in tRNA (Caron et al, 1976) was later reevaluated, and the investigators concluded that the aforementioned conformational alterations did not occur (Rodriguez et al, 1980). Another group has also reported that their s4U8-bound spin labels detected no significant change in the overall tRNA structure upon aminoacylation (Bondarev et al, 1982).…”

Lanthanide fluorescence studies of transfer RNAfMet conformation

“…Differences in tRNAf1^a nd fMet-tRNAf4^c onformation reported by Watanabe & Imahori (1971) must be carefully considered because of the low magnitude of their CD signal. While spin-labeling studies (Caron et al, 1976) indicate that the conformation near s4U in E. coli tRNAphe is altered by aminoacylation, the attachment of a spin-label may affect the conformational nature of the macromolecule. Our results are not directly comparable with those of Caron et al (1976) Bina-Stein & Crothers, 1974,1975.…”

“…While spin-labeling studies (Caron et al, 1976) indicate that the conformation near s4U in E. coli tRNAphe is altered by aminoacylation, the attachment of a spin-label may affect the conformational nature of the macromolecule. Our results are not directly comparable with those of Caron et al (1976) Bina-Stein & Crothers, 1974,1975. We have used the same tRNA species and pH as Watanabe & Imahori (1971).…”

“…Physical chemical evidence for such a conformational change has been sought using tritium exchange (Grant! et al, 1969;Englander etal., 1972), NMR1 * (Cohn etal., 1970;Wong et al, 1973), Raman (Thomas et al, 1973), EPR (Caron et al, 1976), and CD (Adler & Fasman, 1970; Wickstrom, 1971; Watanabe & Imahori, 1971). A clear answer to the problem has yet to be found, but a review of the evidence indicates that, if such a conformational change occurs, it is very subtle and apparently localized in a particular region of tRNA.…”

Spin-labeled nucleic acids

“…A comparison of the EPR spectra of these three differently located spin labels showed that upon aminoacylation of tRNAphe the region around the s4U8 residue and the variable loop region became more flexible, while the environment of the anticodon loop was not affected. 59 This result strongly suggested that the main difference in structure between charged and uncharged tRNA resides is the release and exposure of the T^CG loop (Figure 7) for eventual binding to the complementary sequence CGAA on the 5S RNA in the ribosomes.57,60 This is tantamount to saying that during the normal course of protein biosynthesis some of the tertiary structure of tRNA must be disrupted.58 Therefore, this interesting observation represents an important contribution toward a better understanding of the dynamic role that tRNA plays in Nature. Such a subtle perturbation of tRNA structure upon aminoacylation was not detected by NMR spectroscopy.61 Schwarz et al 62 have proposed a different model whereby codon-anticodon recognition can cause a conformational change on aminoacyl-tRNA, which results in the binding of the T\I>CG sequence to the 50S ribosomal subunit.…”