Biopolymers and cell. 1998; 14 (4): 349 - 359

Structural and functional investigation of mammalian tyrosyl-tRNA synthetase

A. I. Karnelyuk

The main results of the structural and functional investigation of mammalian tyrosyl-tRNA synthetase are reviewed. The multiplicity of molecular forms of enzyme is analyzed. Structure of the. active site of synthetase has been studied by chemical modification methods and the essential, role of lysine, Imtidine and cysteine residues has been revealed. Jt was found that the anticodon of homologous bovine tRNA '' is involved in the interaction witlt the main form of synthetase in the complex. Conformational changes of enzyme in the course of substrate binding, including tRNA recognition have been revealed. On the basis of the data obtained the dynamical model of functioning of tyrosyl-tRNA synthetase has been proposed. Primary structure of bovine tyrosyl-tRNA synthetase has been determined by cDNA cloning and sequencing. The modular organization of tyrosyl-tRNA synthetase is proposed where the catalytic part of enzyme composed by Rossniann fold and a-helical domain is connected to a cytokine-like C-terminaf module. The hypothesis is forwarded about possible forming of the isolated C-domain as a result of the proteolytic digestion after proiease activation and about possible cytokine like activity of this C-domain similar EMAP II cytokine.