Stimulation by Aminoacyl-tRNA of the GTPase and ATPase Activities of Rat Liver 5S RNA Protein Particles in the Presence of EF-21

Abstract

The GTP- and ATP-hydrolyzing activities of the rat liver 5S RNA-L5 (according to the proposed common nomenclature (1)) protein complex designated as 5S RNP were stimulated by pig liver elongation factor 2 (EF-2) plus aminoacyl-tRNA, both of which were required for the stimulation. The stimulative effect of aminoacyl-tRNA on GTP hydrolysis by the complete system containing 5S RNP and EF-2 was dependent on the concentration of aminoacyl-tRNA. Aminoacyl-tRNA also stimulated ATP hydrolysis by the complete system but did not stimulate the ATP hydrolysis by 5S RNP alone or EF-2 alone. While deacylated tRNA stimulated the ATPase activity of the complete system, it had no effect on the GTPase activity. Preincubated tRNA lacking the 3'-terminal CCA moiety had little effect on the GTPase and ATPase activities of the complete system. Fusidic acid inhibited the GTPase and the ATPase activities of the complete system with and without aminoacyl-tRNA, although the extent of the inhibition was larger in the presence of aminoacyl-tRNA. These results suggest that 5S RNP may be a component of the GTPase center of rat liver 60S subunits.