Sedimentation studies on aminoacyl-sRNA synthetase and activation of aminoacyl-sRNA transfer factor

Sucrose density gradient centrifugation analysis of aminoacyl-sRNA transfer factor and aminoacyl-sRNA synthetase revealed that aminoacyl-sRNA transfer factor for various amino acids sedimented similarly, and the sedimentation coefficient was approximately 4 S. While most of the aminoacyl-sRNA synthetases had a sedimentation coefficient of about 8 S, phenylalanyl-sRNA synthetase sedimented differently from other aminoacyl-sRNA synthetases, and it was distributed throughout the density gradient. With this method, phenylalanyl-sRNA synthetase was obtained free from aminoacyl-sRNA transfer factor. An approximately 10-fold activation of aminoacyl-sRNA transfer factor prepared by this method was observed by incubation of the factor with β-mercaptoethanol and bovine serum albumin.