Purification and properties of bovine liver seryl-tRNA synthetase

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Abstract
Seryl-tRNA synthetase was purified 1800-fold from bovine liver extract by ultracentrifugation at 150,000 .times. 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 Matrex gel red A. The relative molecular mass, MW, in the denatured state was estimated as 87,000 by sodium dodecyl sulfate disc gel electrophoresis; in the active state the MW was estimated as 170,000 for the dimeric native enzyme (.alpha.2 type) by chromatography on Sephacryl S-300. The amino acid composition of the enzyme was determined. The Km values for ATP and serine were 0.49 mM and 30 .mu.M, respectively. The Km values for .**GRAPHIC**. and .**GRAPHIC**. were 1.40 .mu.M and 1.25 .mu.M, respectively. Sequences common to the 2 isoaccepting tRNASer molecules are discussed in relation to the recognition mechanism of the purified seryl-tRNA synthetase.