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

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Abstract
Elongation factor Tu (EF-Tu) dependent GTP hydrolysis normally requires the presence of ribosomes and aminoacyl-tRNA (aa-tRNA) [in Escherichia coli]. In the presence of the antibiotic kirromycin, the factor alone displays a GTPase activity that is enhanced by ribosomes and/or aa[aminoacyl]-tRNA. This system showed the following: the 50S ribosomal subunit can substitute the 70S ribosome; the 50S CsCl core a b and c particles lacking an increasing number of proteins, can induce approximately 65, 45 and 25%, respectively, of the EF-Tu.cntdot.kirromycin GTPase activity of control 50S subunits, in the presence of 30S subunits and aa-tRNA; 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.cntdot.kirromycin-dependent GTPase to 70-90% of the control; proteins L7/L12, with or without contaminating L10, did not induce any EF-Tu-dependent GTPase activity, in contrast to a recent report, whether EF-Ts and/or kirromycin were present or not.