PURIFICATION AND CHARACTERIZATION OF LYSYL-TRANSFER RNA-SYNTHETASE AFTER DISSOCIATION OF THE PARTICULATE AMINOACYL TRANSFER RNA-SYNTHETASES FROM RAT-LIVER
The major aminoacyl-tRNA synthetase complex (the 24 S complex) isolated from rat liver, which contains lysyl-, leucyl- and arginyl-tRNA synthetase activities, is dissociated into fully active free aminoacyl-tRNA synthetases by column chromatography on diaminooctyl-Sepharose. During the hydrophobic interaction chromatography, more than a quantitative yield of the lysyl-tRNA synthetase activity is obtained. The free lysyl-tRNA synthetase, dissociated from the synthetase complex, is purified about 2,000-fold with a 13% yield by conventional column chromatography. Lysyl-tRNA synthetase is purified from the 24 S synthetase complex by affinity column chromatography on lysyldiaminohexyl-Sepharose. Free lysyl-tRNA synthetase, as dissociated from the synthetase complex, is evidently a dimeric enzyme with a subunit MW of 66,000 .+-. 3,000, as determined by gel electrophoresis, sucrose gradient centrifugation and gel filtration.