title: Solution conformations of an insect neuropeptide: crustacean cardioactive peptide (CCAP).
abstract: The solution structure of crustacean cardioactive peptide (CCAP), a cyclic amidated nonapeptide neurohormone, was studied using molecular dynamics techniques, with constraints derived from NMR studies in water and water/dodecylphosphocholine micellar medium. This peptide, found in various invertebrates, has the primary sequence Pro(1) Phe(2) Cys(3) Asn(4) Ala(5) Phe(6) Thr(7) Gly(8) Cys(9) NH(2), with an intramolecular disulfide bridge between the two cysteine residues. In aqueous solution the peptide was found to have a type(IV) beta-turn between residues 5-8. In a water/decane biphasic medium a type(IV) beta-turn between residues 3 and 6 and two classic gamma-turns between residues 4-6 and 7-9, were found. Analysis of the (1)H and (13)C NMR chemical shifts data showed that the model free S(2) order parameter of the residues varied between 0.65 and 0.9. The molecular dynamic root mean square fluctuations of structural ensembles of the backbone varied between 0.5 and 2.2 with the central residues showing the least fluctuations.
authors.affiliation: Chemistry Department, University of Cape Town, Private Bag, 7701 Rondebosch, Cape Town, South Africa. graham.jackson@uct.ac.za
authors.forename: Graham E
authors.initials: GE
authors.lastname: Jackson
authors.forename: Andre N
authors.initials: AN
authors.lastname: Mabula
authors.forename: Shane R
authors.initials: SR
authors.lastname: Stone
authors.forename: Gerd
authors.initials: G
authors.lastname: Gäde
authors.forename: Katalin E
authors.initials: KE
authors.lastname: Kövér
authors.forename: László
authors.initials: L
authors.lastname: Szilágyi
authors.forename: David
authors.initials: D
authors.lastname: van der Spoel
mesh_terms: D000818:Animals; D003198:Computer Simulation; D008958:Models, Molecular; D009479:Neuropeptides / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D012996:Solutions
chemical_list: D009479:Neuropeptides; D012996:Solutions; C058620:crustacean cardioactive peptide