title: Mechanism of protein synthesis inhibition by didemnin B in vitro.
abstract: The cytotoxic and immunosuppressive marine depsipeptide didemnin B is a potent inhibitor of protein biosynthesis in intact cells. Here, didemnin B is shown to inhibit protein synthesis in vitro during the elongation cycle, by preventing eukaryotic elongation factor 2-(eEF-2-) dependent translocation. No inhibition of aminoacyl-tRNA delivery or of peptidyltransferase activity is observed. Didemnin B stimulates eEF-1 alpha-dependent aminoacyl-tRNA binding to rabbit reticulocyte ribosomes, and eEF-1 alpha is required for inhibition of the subsequent translocation of phenylalanyl-tRNA(Phe) from the A- to the P-site. These observations suggest that didemnin B prevents translocation by stabilizing aminoacyl-tRNA bound to the ribosomal A-site, similar to the antibiotic kirromycin, and consistent with the known affinity of didemnins for elongation factor eEF-1 alpha [Crews et al. (1994) J. Biol. Chem. 269, 15411]. Unlike kirromycin, didemnin B does not prevent peptide bond formation, so inhibition is observed only at the translocation step. Inhibition of translocation by didemnin B is attenuated by increasing concentrations of eEF-2.
authors.affiliation: Willard H. Dow Laboratory, Department of Chemistry, University of Michigan, Ann Arbor 48109-1055, USA.
authors.forename: B V
authors.initials: BV
authors.lastname: SirDeshpande
authors.forename: P L
authors.initials: PL
authors.lastname: Toogood
mesh_terms: D000818:Animals; D001665:Binding Sites; D047630:Depsipeptides; D066298:In Vitro Techniques; D010441:Peptide Chain Elongation, Translational / Q000187:drug effects; D020652:Peptide Elongation Factor 2; D010445:Peptide Elongation Factors / Q000378:metabolism; D010456:Peptides, Cyclic / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D011500:Protein Synthesis Inhibitors / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism; D012360:RNA, Transfer, Phe / Q000378:metabolism; D011817:Rabbits; D012156:Reticulocytes / Q000187:drug effects / Q000378:metabolism; D012270:Ribosomes / Q000187:drug effects / Q000378:metabolism
chemical_list: D047630:Depsipeptides; D020652:Peptide Elongation Factor 2; D010445:Peptide Elongation Factors; D010456:Peptides, Cyclic; D011500:Protein Synthesis Inhibitors; D012346:RNA, Transfer, Amino Acyl; D012360:RNA, Transfer, Phe; C030051:didemnins