title: Characterization of the elongation factors from calf brain. 2. Functional properties of EF-1 alpha, the action of physiological ligands and kirromycin.
abstract: The properties of EF-1 alpha from calf brain have been investigated and compared with those of EF-Tu. EF-1 alpha binds GDP and GTP in a 1:1 stoichiometry, showing the same affinity for both nucleotides (K'd = 2-4 microM). EF-1 beta strongly enhances the dissociation rate of the EF-1 alpha X GDP complex and to a lesser extent of the EF-1 alpha X GTP complex. Aminoacyl-tRNA (aa-tRNA) stabilized EF-1 alpha X GTP much less efficiently than the EF-Tu X GTP complex. Unlike EF-Tu, EF-1 alpha sustains the binding of aa-tRNA to the ribosome also in the presence of GDP or in the absence of any nucleotide, though to a lesser degree than with GTP. Kirromycin enhances the dissociation rate of both EF-1 alpha X GTP and EF-1 alpha X GDP but especially that of the latter. This effect results in an increase of the exchange rate of the EF-1 alpha-bound nucleotide with free nucleotides. Although in this regard the effect of kirromycin mimics that of EF-1 beta, the antibiotic is incapable of increasing the EF-1 alpha X GDP/GTP exchange rate when aa-tRNA and ribosomes are present. Therefore, unlike EF-1 beta, kirromycin cannot enhance the rate of poly(Phe) synthesis. On the other hand, the failure of kirromycin to induce a GTP-like conformation of EF-1 alpha X GDP, as in the case of EF-Tu X GDP, explains its inability to inhibit peptide bond formation in the eukaryotic system.
mesh_terms: D000818:Animals; D001923:Brain Chemistry; D002417:Cattle; D003840:Deoxycholic Acid; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D007700:Kinetics; D008024:Ligands; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors / Q000378:metabolism*; D011485:Protein Binding; D011728:Pyridones / Q000494:pharmacology; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism / Q000494:pharmacology
chemical_list: D008024:Ligands; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors; D011728:Pyridones; D012346:RNA, Transfer, Amino Acyl; D003840:Deoxycholic Acid; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; C008536:mocimycin