Purification and properties of bovine liver seryl-tRNA synthetase.

Seryl-tRNA synthetase was purified 1800-fold from bovine liver extract by ultracentrifugation at 150000 x g, chromatography on DEAE-cellulose, fractional precipitation with ammonium sulfate, gel chromatography on Sephacryl S-300, adsorption chromatography on hydroxyapatite, affinity chromatography on blue-Sepharose and finally on M&asline;trex gel red A. The relative molecular mass, M_r, in the denatured state was estimated as 87000 by sodium dodecyl sulfate disc gel electrophoresis; in the active state the M_r was estimated as 170000 for the dimeric native enzyme (α₂ type) by chromatography on Sephacryi S-300. The amino acid composition of the enzyme was determined. The K_m values for ATP and serine were 0.49 mM and 30 μM, respectively. The K_m values for tNA_IGA^Ser and tRNA_cmCA^Ser were 1.40 μM and 1.25 μM, respectively. Sequences common to the two isoaccepting tRNA^Ser molecules are discussed in relation to the recognition mechanism of the purified seryl-tRNA synthetase. [ABSTRACT FROM AUTHOR]