title: Ubiquitin carboxyl-terminal peptides. Substrates for ubiquitin activating enzyme.
abstract: The carboxyl terminus of ubiquitin is activated in the presence of ATP to enter the ubiquitin cycle in cells. Peptides corresponding to the COOH-terminal region of ubiquitin were synthesized to investigate their effects on the ATP/ubiquitin-dependent proteolytic pathway. Their activities in the PPi exchange assay with ubiquitin activating enzyme (E1) were proportional to their length. The hexapeptide Ac-Leu-Arg-Leu-Arg-Gly-Gly reacted with ATP to form an enzyme-adenylate-hexapeptide complex and at high concentrations was 20-25% as active as human ubiquitin in the PPi exchange assay with E1. However, the hexapeptide was not transferred to the sulfhydryl "thiol" site on E1. In addition, the COOH-terminal peptides did not support the degradation of 125I-bovine serum albumin in the reticulocyte lysate system. A nonhomologous peptide of equivalent length was inactive in all assays. Thus, synthetic COOH-terminal peptide(s) of ubiquitin can partially substitute for ubiquitin in its reactions with E1 but do not support subsequent steps of the energy-dependent proteolytic pathway. These results show that it may be possible to design small molecules that either serve as substrates or inhibitors for other specific steps in ubiquitin-dependent pathways.
authors.affiliation: Department of Molecular Pharmacology, Smith Kline and French Laboratories, Philadelphia, Pennsylvania 19101.
authors.forename: S
authors.initials: S
authors.lastname: Jonnalagadda
authors.forename: D J
authors.initials: DJ
authors.lastname: Ecker
authors.forename: E J
authors.initials: EJ
authors.lastname: Sternberg
authors.forename: T R
authors.initials: TR
authors.lastname: Butt
authors.forename: S T
authors.initials: ST
authors.lastname: Crooke
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002417:Cattle; D006868:Hydrolysis; D008025:Ligases / Q000378:metabolism*; D008956:Models, Chemical; D009842:Oligopeptides / Q000378:metabolism*; D012156:Reticulocytes / Q000201:enzymology; D044764:Ubiquitin-Activating Enzymes; D044767:Ubiquitin-Protein Ligases; D014452:Ubiquitins / Q000378:metabolism*
chemical_list: D009842:Oligopeptides; D014452:Ubiquitins; D000255:Adenosine Triphosphate; D044767:Ubiquitin-Protein Ligases; D008025:Ligases; D044764:Ubiquitin-Activating Enzymes