title: Initiation factor IF2, thiostrepton and micrococcin prevent the binding of elongation factor G to the Escherichia coli ribosome.
abstract: The bacterial translational GTPases (initiation factor IF2, elongation factors EF-G and EF-Tu and release factor RF3) are involved in all stages of translation, and evidence indicates that they bind to overlapping sites on the ribosome, whereupon GTP hydrolysis is triggered. We provide evidence for a common ribosomal binding site for EF-G and IF2. IF2 prevents the binding of EF-G to the ribosome, as shown by Western blot analysis and fusidic acid-stabilized EF-G.GDP.ribosome complex formation. Additionally, IF2 inhibits EF-G-dependent GTP hydrolysis on 70 S ribosomes. The antibiotics thiostrepton and micrococcin, which bind to part of the EF-G binding site and interfere with the function of the factor, also affect the function of IF2. While thiostrepton is a strong inhibitor of EF-G-dependent GTP hydrolysis, GTP hydrolysis by IF2 is stimulated by the drug. Micrococcin stimulates GTP hydrolysis by both factors. We show directly that these drugs act by destabilizing the interaction of EF-G with the ribosome, and provide evidence that they have similar effects on IF2.
authors.affiliation: School of Microbiology and Immunology, University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Dale M
authors.initials: DM
authors.lastname: Cameron
authors.forename: Jill
authors.initials: J
authors.lastname: Thompson
authors.forename: Paul E
authors.initials: PE
authors.lastname: March
authors.forename: Albert E
authors.initials: AE
authors.lastname: Dahlberg
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001430:Bacteriocins; D001667:Binding, Competitive; D015153:Blotting, Western; D004926:Escherichia coli; D029968:Escherichia coli Proteins / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D006868:Hydrolysis / Q000187:drug effects; D009154:Mutation; D020653:Peptide Elongation Factor G / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010448:Peptide Initiation Factors / Q000378:metabolism*; D010455:Peptides; D039881:Prokaryotic Initiation Factor-2; D011485:Protein Binding / Q000187:drug effects*; D012338:RNA, Ribosomal, 23S / Q000235:genetics / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism*; D013883:Thiostrepton / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D001430:Bacteriocins; D029968:Escherichia coli Proteins; D020653:Peptide Elongation Factor G; D010448:Peptide Initiation Factors; D010455:Peptides; D039881:Prokaryotic Initiation Factor-2; D012338:RNA, Ribosomal, 23S; D012269:Ribosomal Proteins; C027624:ribosomal protein L11; C009779:micrococcin; D006160:Guanosine Triphosphate; D013883:Thiostrepton