Biopolymers and cell. 1986. Volume 2. № 1. 12 - 19
T. I. Merkulova, M. K. Nurbekov, G. K. Kovaleva
STUDY OF ATP AND PYROPHOSPHATE-BINDING SITES OF TRYPTOPHANYL-tRNA SYNTHETASE BY PHOSPHONATE ANALOGS OF ATP AND PYROPHOSPHATE
Summary
ATP and pyrophosphate-binding sites of bovine tryptophanyl-tRNA-synthetase were studied by phosphonate analogs of ATP and inorganic pyrophosphate — adenosyl-5'-phospho-ryldiphosphonate (Appcp), adenosyl-5'-diphosphonylphosphate (Apcpp) and methylene-diphosphonate (PcP). Methylenediphosphonate can fulfil the role of PP; in the reaction of tryptophanyl adenylate pyrophosphorolysis with the formation of Appcp, the only product of the reaction. Phosphonate analogs of ATP inhibit the reaction of tryptophan-dependent ATP-[32P]PP,- exchange competitively with respect both to ATP (K;~0.7 mM for Apcpp and ~3.6 mM for Appcp) and PP; (Ki~2.5 mM for both inhibitors). The two analogs interact with the isolated tryptophanyl adenylate-enzyme complex, corresponding phosphonate analogs of Ap4A being formed. On the basis of the results obtained an assumption is made that the observed earlier enzyme pyrophosphorylation by pyrophosphate, which is cleft from ATP in the course of adenylate formation, may be one of the factors preventing the synthesis of Ap4A on tryptophanyl-tRNA synthetase.