Protection of bovine seryl-transfer ribonucleic acid (seryl-tRNA) synthetase from chemical modification by its substrates, and some kinetic parameters.

Abstract

Amino acid residues contained in the recognition sites of seryl-transfer ribonucleic acid (tRNA) synthetase (SerRS) were studied by chemical modification.Ser residues were modified with phenylmethanesulfonyl fluoride, and appeared to be unnecessary for the recognition. However, the modification of Arg residues with phenylglyoxal, His residues with diethylpyrocarbonate and sulfhydryl groups with 5,5'-dithiobis(2-nitrobenzoic acid), N-ethylmaleimide, iodoacetic acid or iodoacetamide showed that these residues were essential for the tRNA recognition by SerRS. Protection experiments with substrates from inactivation of Ser-tRNA formation by modification suggested that Arg residues interact with the y-phosphate of adenosine triphosphate and tRNA .Modification of sulfhydryl groups showed that the groups interact with the hydroxyl groups of ribose of the CCA-end on tRNA. Furthermore, in order to understand the recognition mechanism between SerRS and tRNAser, some kinetic parameters such as the Km and V. values of yeast tRNAs" and E. coli tRNAser for bovine SerRS were compared with the values of bovine tRNAser .

Genomic Organization, cDNA Sequence, Bacterial Expression, and Purification of Human Seryl‐tRNA Synthase

“…The recombinant human seryl-tRNA synthetase cross-charges E. coli tRNA in vitro, whereas E. coli seryl-tRNA synthetase is unable to aminoacylate calf liver tRNA in vitro. Consistent with our results, similar observations have been reported for yeast seryl-tRNA synthetase (Weygand-Durasevic et al, 1987) and bovine liver seryltRNA synthetase (Tachibana and Mizutani, 1988) with E. coli tRNA. Kinetic parameters determined with E. coli tRNA have shown that it is not an efficient substrate for yeast and bovine seryl-tRNA synthetases.…”

“…In addition, the eukaryotic aminoacyl-tRNA synthetases contain N-terminal extensions, but only eukaryotic isoleucyl-tRNA synthetase (Shiba et al, 1994;Nichols et al, 1995) and seryl-tRNA synthetases possess extra C-terminal domains (Weygand-Durasevic et al, 1996). Seryl-tRNA synthetases, of diverse vertebrate origins, have been studied at the biochemical and structural levels for the last two and a half decades (Le Meur et al, 1972;Rouge et al, 1969;Mizutani et al, 1984;Tachibana and Mizutani, 1988). For the chicken liver seryl-tRNA synthetase (Le Meur et al, 1972) a molecular mass of about 120 kDa has been reported for an enzyme composed of two identical subunits.…”