ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Electron paramagnetic resonance spectroscopy has been used to study the coupling of Mn2+ ions with the tRNAVal1 modified with a spin label at four pseudouridylic residues and with the valyl-tRNAVal1 modified with a spin label at the α-amine group of the valyl residue. A sharp increase of spin-label mobility has been found in these samples, due to the conformational transition induced by the first and second Mn2+ ions. Analysis of dipole-dipole couplings of spin labels with the coordinated ions revealed a definite order in the occupation of ion coordination sites in the tRNA. For some valyl-tRNAVal1 molecules, the second Mn2+ ions were shown to coordinate on the α-amine group of the valyl residue at a distance of 15-25 Å from a spin label. As a result of the conformational transition, a coordination site appeared in the tRNA at one of the pseudouridylic residues, its distance from the spin label being less than 10 Å. It has been suggested that the conformational transition induced by ions excluded some bases from the system of hydrogen bonds at the level of the tRNA tertiary structure. As a result, these bases acquired sufficient sterical freedom to participate in the Mn2+ ion coordination.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.1975.360141202
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