title: Immunosuppressory activity of ubiquitin fragments containing retro-RGD sequence.
abstract: A peptide fragment corresponding to the ubiquitin(50-59) sequence (LEDGRTLSDY) (U50-59) possesses a very high immunosuppressory activity, comparable to that of cyclosporine, both in the cellular and humoral immune responses. We found that the pentapeptide DGRTL (U52-56) is the shortest, effective immunosuppressory fragment of ubiquitin, although its potency is weaker than that of U50-59. Replacement of each consecutive residue with alanine in U52-56 allowed identification of essential amino acids involved in the immunosuppression. We also evaluated the roles of its N- and C-terminal groups by their acetylation and/or amidation, respectively. The active sequence is located in the external loop of the molecule and therefore it may serve as an important functional epitope for intermolecular binding. Based on the crystal structure of ubiquitin molecule, we designed and synthesized the cyclic analogue with a restricted conformation, cyclo(Glt-Gln-Leu-Glu-Asp-Gly-Arg-Thr-Leu-Ser-Asp-Lys)-NH2 (Glt = glutaryl) by reacting the C-terminal Lys side chain with the glutarylated N-terminus. The peptide was designed to mimic the ubiquitin(48-59) loop, in order to obtain the ligand that may interact with hypothetical receptors of the loop. The cyclization product selectively but strongly suppresses the cellular immune response. The results indicate that the 48-59 loop may serve as an important functional epitope in the ubiquitin molecule for intermolecular binding.
authors.affiliation: Faculty of Chemistry, University of Wrocław, Wrocław, Poland. szewczuk@wchuwr.chem.uni.wroc.pl
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Szewczuk
authors.forename: Piotr
authors.initials: P
authors.lastname: Stefanowicz
authors.forename: Andrzej
authors.initials: A
authors.lastname: Wilczyński
authors.forename: Anna
authors.initials: A
authors.lastname: Staszewska
authors.forename: Ignacy Z
authors.initials: IZ
authors.lastname: Siemion
authors.forename: Michał
authors.initials: M
authors.lastname: Zimecki
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Wieczorek
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002942:Circular Dichroism; D016572:Cyclosporine / Q000494:pharmacology; D006801:Humans; D007166:Immunosuppressive Agents / Q000737:chemistry* / Q000494:pharmacology*; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D011487:Protein Conformation; D025801:Ubiquitin / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*
chemical_list: D007166:Immunosuppressive Agents; D009842:Oligopeptides; D010446:Peptide Fragments; D025801:Ubiquitin; C489230:ubiquitin 50-59, human; C047981:arginyl-glycyl-aspartic acid; D016572:Cyclosporine