Tritium exchange on transfer RNA: slowly exchanging protons sensitive to a change in the dihydrouridine stem.

Publisher Website
Google Scholar
Abstract
Measurements of tritium exchange on tRNA (extracted from Escherichia coli) were made for periods from 0.5 min-8 h after separation from labeled solvent. The exchange curve was analyzed in terms of 3 kinetic classes of exchanging protons with half-lives of 5 h (12 protons), 0.54 h (37 protons) and about 3.5 min (58 protons) at 0.degree. C in 0.14 M K+/10 mM Mg2+. The behavior under varying ionic conditions of protons in the slowest exchange class and of some protons in the intermediate class suggests that they are dependent on the tertiary structure of the molecule. In the same range of exchange times characteristic of these latter protons, about 9 more protons were observed in the case of a mutant form of tRNATrp, the UGA-suppressor species, than in the wild-type tRNATrp. These 2 species differ only in base 24 in the dihydrouridine stem. This dynamic difference between the wild-type and suppressor species may be related to a functionally important difference in coupling between the conformation of the molecule and interactions at the anticodon.