The isolation and biological activity of multiple forms of aminoacyl transferase I of rat liver

Abstract

A method for the isolation of aminoacyl transferase I was developed using hydroxylapatite, which yielded a preparation of this transfer factor containing less transferase II and less extraneous protein than previous preparations. The transferase I isolated was resolved by gel filtration into three protein-containing fractions, all of which catalyzed the incorporation of amino acids from aminoacyl-tRNA to ribosome-bound polypeptides in the presence of transferase II. All three were inactivated by incubation with GTP in the absence but not in the presence of aminoacyl-tRNA. These separate forms of transferase I differed in their apparent molecular weights and in their relative specific activities. Incubation of one of the high molecular weight forms of transferase I with NH 4Cl led to its conversion to a lower molecular weight form and, on prolonged incubation, to a loss of activity.