Search PubMed⌕ Search

Biomedical subjects

D R Kearns

Publications and source records attributed to D R Kearns.

At least 109 records · Page 6Linked to original sources
PubMed1975

NMR investigation of the effect of selective modifications in the anticodon loop on the conformation of yeast transfer RNA-Phe.

Changes in the 300 MHz proton NMR spectrum of yeast tRNA-Phe induced by the removal of the Y-base from the anticodon loop are reversed when the dye proflavine is incorporated in its place. These observations correlate with our earlier interpretation of the NMR data that removal of the Y-base causes a change in the conformation of the anticodon stem. Such changes in stem conformation may in part be responsible for the differences in the biochemical properties of tRNA-Phe, tRNA-PhePF and tRNA-Phe-Y.

Anticodon↗
PubMed1975

Europium as a fluorescent probe of transfer RNA structure.

The binding of europium(III) to Escherichia coli tRNA-fMet,Glu and to unfractionated E. coli tRNA has been investigated by using the 4-thiouridine sensitization of europium 5-Do yields 7-F1 emission and changes in the lifetime of the 5-Do state of europium reported earlier (J. M. Wolfson and D. R. Kearns (1974), J. Am. Chem. Soc. 96, 3653). Binding of the first 3-4 europium ions is independent and sequential, approximately 600 times stronger than the magnesium binding, and the binding sites are located near the 4-thiouridine residue found at position 8 in a number of E. coli tRNA. Competition experiments suggest the strong binding sites are the same for magnesium and europium. The europium binding properties of both unfractionated E. coli tRNA and purified tRNA-fMet are quite similar, indicating that the location of the strong binding sites and their binding constants are nearly the same for a large group of tRNA. The europium binding properties of native and denatured tRNA are quite different, however.

Binding Sites↗
PubMed1975

Tertiary structure in E. coli tRNA Arg and tRNA Val.

300 MHz proton NMR has been used to demonstrate that both Escherichia coli tRNA Arg and tRNA(1) Val have a tertiary structure base pair between 4-thiouridine (s-4U) at position 8 and A at position 14. Formation of this s-4U(8)-A(14) base pair leads to a very low field (14.8 ppm) resonance in the spectra of both molecules. When s-4U is converted to U the 14.8 resonance is replaced by a new resonance which appears at 14.3 ppm. The presence of the tertiary structure s-4U(8)-A(14) base pair greatly constrains the folding of these tRNAs in solution.

Arginine↗
PubMed1974

Investigation of the structure of yeast tRNAphe by nuclear magnetic resonance: paramagnetic rare earth ion probes of structure.

The binding of paramagnetic rare earth ions to yeast tRNA(Phe) shifts some resonances in the low-field nuclear magnetic resonance spectrum that have been assigned to ring nitrogen protons of specific Watson-Crick base pairs. The changes in the nuclear magnetic resonance spectrum as the tRNA is titrated with Eu(3+) indicate that 4 (or 5) Eu(3+) ions are tightly bound, that the metal binding is in the fast exchange limit, and that the binding to different sites in the molecule is sequential rather than cooperative. The first metal bound simultaneously shifts resonances associated with the dihydrouridine and the -C-C-A stem. This permits us to conclude that the folding of the tRNA(Phe) in solution brings the phosphate backbone of the -C-C-A and the dihydrouridine stems into close proximity. A model of the three-dimensional structure of tRNA(Phe) incorporating this new information appears to be compatible with the results obtained from x-ray diffraction.

Europium↗