title: Synthesis and bioactivity studies of two isosteric acyclic analogues of melanin concentrating hormone.
abstract: Salmon melanin concentrating hormone (MCH) is a cyclic heptadecapeptide. MCH stimulates perinuclear aggregation of melanosomes within integumental melanocytes of teleost fishes resulting in skin blanching. MCH contains a disulfide bridge forming a 10-residue ring [sequence: see text]. It has been proposed that the ring is necessary for maintenance of potency. In order to test this proposal, we have synthesized two pseudo-isosteric analogues of MCH that cannot cyclize. They differed only in the polarity of the side chain group of positions 5 and 14. Serine was substituted for Cys5 and Cys14 in one peptide and L alpha-aminobutyrate (Abu) was the substitution at the two positions in the other peptide. Using a fish skin bioassay we determined that these analogues exhibit less than 1/10,000th the potency of the native hormone. These results suggest that the disulfide bridge is necessary to maintain the correct conformational and topographical features of the hormone for receptor binding and transmembrane signal transduction.
authors.affiliation: Department of Chemistry University of Arizona, Tucson 85721.
authors.forename: T O
authors.initials: TO
authors.lastname: Matsunaga
authors.forename: V J
authors.initials: VJ
authors.lastname: Hruby
authors.forename: M
authors.initials: M
authors.lastname: Lebl
authors.forename: A M
authors.initials: AM
authors.lastname: Castrucci
authors.forename: M E
authors.initials: ME
authors.lastname: Hadley
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004524:Eels; D007028:Hypothalamic Hormones; D066298:In Vitro Techniques; D007202:Indicators and Reagents; D008543:Melanins / Q000138:chemical synthesis* / Q000494:pharmacology*; D008544:Melanocytes / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D008969:Molecular Sequence Data; D010907:Pituitary Hormones / Q000138:chemical synthesis* / Q000494:pharmacology*; D016339:Spectrometry, Mass, Fast Atom Bombardment; D013329:Structure-Activity Relationship
chemical_list: D007028:Hypothalamic Hormones; D007202:Indicators and Reagents; D008543:Melanins; D010907:Pituitary Hormones; C019463:melanin-concentrating hormone