Interaction of elongation factor Tu with the ribosome. A study using the antibiotic kirromycin

Elongation factor Tu (EF-Tu) dependent GTP hydrolysis normally requires the presence of ribosomes and aminoacyl-tRNA (aa-tRNA). In the presence of the antibiotic kirromycin, the factor alone displays a GTPase activity that is enhanced by ribosomes and/or aa-tRNA [Wolf, H., Chinali, G., & Parmeggiani, A. (1974) Proc. Natl. Acad. Sci. U.S.A. 71, 4910-4914]. Using this system, we have found the following: (1) the 50S ribosomal subunit can substitute the 70S ribosome; (2) the 50S CsCl core a, b, and c particles [Sander, G., Marsh, R. C., Voigt, J., & Parmeggiani, A. (1975) Biochemistry 14, 1805-1814], lacking an increasing number of proteins, can induce ca. 65, 45, and 25%, respectively, of the EF-Tu-kirromycin GTPase activity of control 50S subunits, in the presence of 30S subunits and aa-tRNA; (3) addition of proteins L7/L12 with L10, but not of proteins L7/L12 free from L10, restored the activity of all the 50S CsCl cores in the EF-Tu-kirromycin-dependent GTPase to 70-90% of the control; (4) proteins L7/L12, with or without contaminating L10, did not induce any EF-Tu-dependent GTPase activity, in contrast to a recent report [Donner, D., Villems, R., Liljas, A., & Kurland, C. G. (1978) Proc. Natl. Acad. Sci. U.S.A. 75, 3192-3195], whether EF-Ts and/or kirromycin were present or not.