Yeast phenylalanine tRNA (tRNAPhe) exhibits a 4$-fold enhancement of fluorescence in response to the addition of Mg2+. Concurrently, over the same concentration range (0 to 0.4 m&r) of Mg2+, the circular dichroism peak at 263 nm displays a 20% increase in ellipticity and a blue shift of 2 nm. The existence of the negative circular dichroism band at 295 nm appears to be cation-dependent. This co...

The N3 imino units of dihydrouridine were identified in samples of I5N-Iabeled Escherichia coli tRNAret, tRNALy., and tRNAPhe by IH_15N two-dimensional NMR. The peaks for dihydrouridine had high field 1 H (9.7-9.8 ppm) and I5N (147.8-149.5 ppm) chemical shifts. Assignments were made by IH_IoN chemical shift correlation based on values obtained in model studies with tri-O-benzoyland tri-O-acetyl...

Temperature-dependent lowfield proton magnetic resonance spectra of yeast tRNAPhe were recorded between 10 and 15 parts per million. Seven resonances of hydrogen-bonded protons disappeared reversibly under two sets of conditions where the selective broadening of tertiary structure resonances were predicted by temperature jump experiments. The seven resonances were assigned to the seven tertiary...

Yeast tRNAPhe, Yeast tRNATyr, Pyridoxal-5'-phosphate Yeast tRNAPhe and tRNATyr were reacted with the fluo­ rescent reagent pyridoxal-5'-phosphate and the modified tRNAs were analysed with respect to the number and posi­ tion of modified nucleosides and with respect to aminoacylation. a) Following the intrinsic fluorescence of pyridoxal-5'phosphate, the treatment of tRNATyr with increasing amoun...

Depending on the HIV-1 isolate, MN or BH10, the nucleocapsid protein, NCp7, corresponds to a 55- or 71-amino acid length product, respectively. The MN NCp7 contains a single Trp residue at position 37 in the distal zinc finger motif, and the BH10 NCp7 contains an additional Trp, at position 61 in the C-terminal chain. The time-resolved intensity decay parameters of the zinc-saturated BH10 NCp7 ...

Modification defects in the tRNA anticodon loop often impair yeast growth and cause human disease. In the budding yeast Saccharomyces cerevisiae and the phylogenetically distant fission yeast Schizosaccharomyces pombe, trm7Δ mutants grow poorly due to lack of 2'-O-methylation of C32 and G34 in the tRNAPhe anticodon loop, and lesions in the human TRM7 homolog FTSJ1 cause non-syndromic X-linked i...

In the initiation of reverse transcription in retroviruses, nucleocapsid (NC) protein accelerates the rate of annealing of transfer RNA replication primer to a complementary sequence on the genomic RNA. In this report, we have probed the conformational changes induced by HIV-1 NC protein and domain deletion mutants in a structurally well-characterized transfer RNA, yeast tRNAPhe, as a model for...

The overall structure of transfer RNA is optimized for its various functions by a series of unique post-transcriptional nucleotide modifications. Since many of these modifications are conserved from prokaryotes through higher eukaryotes, it has been proposed that most modified nucleotides serve to optimize the ability of the tRNA to accurately interact with other components of the protein synth...

Programmed 30 S subunits expose only one binding site, to which the different classes of tRNA (deacylated tRNAPhe, Phe-tRNAPhe, and N-acetylphenylalanyl (AcPhe)-tRNAPhe) bind with about the same affinity. Elongation factor Tu within the ternary complex does not contribute to the binding of Phe-tRNA. Binding of acylated or deacylated tRNA to 30 S depends on the cognate codon; nonprogrammed 30 S ...

The distance between the corner of the L-shaped transfer RNA and the GTP bound to elongation factor Tu (EF-Tu) in the aminoacyl-tRNA.EF-Tu.GTP ternary complex was measured using fluorescence energy transfer. The donor dye, fluorescein (Fl), was attached covalently to the 4-thiouridine base at position 8 of tRNAPhe, and aminoacylation yielded Phe-tRNAPhe-Fl8. The ribose of GTP was covalently mod...