Macromolecular Complexes of Aminoacyl‐tRNA Synthetases from Eukaryotes

Abstract

Starting from homogenates of sheep liver, extensive co-purification of 7 aminoacyl-tRNA synthetases to high specific activities was achieved by a 3-step procedure involving fractional precipitation by poly(ethylene glycol) 6000, gel filtration on 6% agarose, and chromatography on Sepharose-bound tRNA. The purified material is composed of 9 major protein components as revealed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and has an apparent MW of about 106 estimated by gel filtration on 6% agarose. It contains aminoacyl-tRNA synthetase activities specific for methionine, lysine, arginine, leucine, isoleucine, glutamine and glutamic acid. The rigorous co-elution of these 7 enzymes at each chromatographic step suggests that they are physically associated within the same complex. The enzyme composition of the high MW complex purified from sheep liver is identical to that of the complex previously isolated from human placenta by Denney in 1977.