32P-labeling of bovine tryptophanyl-tRNA synthetase with [32P] Pyrophosphate

RNA-protein interactions at the initial and terminal stages of protein biosynthesis as investigated by Lev Kisselev (on the occasion of his 70th anniversary)

This review highlights studies by Lev L. Kisselev and his colleagues on the initial and terminal stages of protein biosynthesis, which cover the period of the last 45 years (1961-2006). They investigated spatial structure of tRNAs, structure and functions of aminoacyl-tRNA-synthetases of higher organisms, and the final step of protein synthesis, termination of translation. L. Kisselev and his team have made three major contributions to these fields of molecular biology; (i) they proposed the hypothesis on the role of anticodon triplet of tRNA in recognition by cognate aminoacyl-tRNA synthetase, which has been experimentally confirmed and is now included in textbooks; (ii) identified primary structures and functions of two eukaryotic protein factors (eRF1 and eRF3) playing a pivotal role in translation termination; (iii) characterized a structural basis for stop codon recognition by eRF1 within the ribosome and discovered the negative structural elements of eRF1, limiting its recognition of one or two stop-codons.

Catalytical mechanism of the phenylalanyl-tRNA synthetase from yeast. Reactivity of ATP in the absence of phenylalanine

Phenylalanyl-tRNA synthetase catalyses an AMP-ATP exchange under conditions where no aminoacylation of tRNA occurs. A plausible explanation for this reaction had not been given so far. The results of the present investigation provide evidence for the following interpretation. tRNAPhe induces a polarisation of the ATP in complex with the enzyme; this stimulates (a) the formation of phenylalanyl-adenylate in the presence of phenylalanine, (b) the hydrolysis of ATP in the absence of phenylalanine and AMP and (c) the transfer of diphosphoryl onto AMP in the presence of AMP, especially when phenylalanine is absent.

An investigation of the mechanism of activation of tryptophan by tryptophanyl-tRNA synthetase from beef pancreas

Adenosine (S)-5'-[alpha-17O, 18O2]triphosphate has been synthesized and used to investigate the stereochemical course of activation of tryptophan by tryptophanyl-tRNA synthetase from beef pancreas. It is shown that the reaction proceeds by displacement of Mg pyrophosphate from MgATP with inversion of configuration at P alpha. Tryptophanyl-tRNA synthetase catalyses positional isotope exchange in adenosine 5'-[beta-18O2]triphosphate in the presence of tryptophan but not in its absence or in the presence of the competitive inhibitors tryptamine and tryptophanol. These observations eliminate a multi-adenylyl transfer or dissociative mechanism and in combination with the sterochemical study leave a direct associative 'in line' displacement at P alpha of MgATP as the only tenable mechanism for the activation of tryptophan by tryptophanyl-tRNA synthetase.