title: Crystal structure and molecular conformation of achatin-I (H-Gly-D-Phe-Ala-Asp-OH), an endogenous neuropeptide containing a D-amino acid residue.
abstract: In order to investigate the active conformation of achatin-I (H-Gly-D-Phe-Ala-Asp-OH), an endogenous neuropeptide from the Achatina fulica ganglia, its crystal structure and molecular conformation were analysed by the X-ray diffraction method. Crystals from methanol/dioxane are monoclinic, space group P2(1) with a = 5.083(1), b = 9.125(1), c = 20.939(3) A, beta = 94.73(1) degrees. The structure was solved by direct methods and refined to R = 0.051 for 1714 independent reflections with /Fo/ greater than sigma (Fo). The molecule exists as a zwitterion with the Gly N-terminal end protonated and Asp beta-carboxyl deprotonated; the C-terminal of Asp is in a neutral state. The molecule takes a kind of beta turn structure with the D-Phe-Ala residues at the corner of the bend. This turn conformation is primarily formed by the strong intramolecular hydrogen bonds of NH(Gly)...O delta 1 (Asp) and NH(Asp)...O delta 1 (Asp) pairs, thus forming a 15-membered ring structure. Judging from the published data concerning the structure-activity relationship, this turn conformation may reflect an important feature related to the neuroexcitatory activity of achatin-I.
authors.affiliation: Department of Physical Chemistry, Osaka University of Pharmaceutical Sciences, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Ishida
authors.forename: Y
authors.initials: Y
authors.lastname: In
authors.forename: M
authors.initials: M
authors.lastname: Doi
authors.forename: M
authors.initials: M
authors.lastname: Inoue
authors.forename: Y
authors.initials: Y
authors.lastname: Yasuda-Kamatani
authors.forename: H
authors.initials: H
authors.lastname: Minakata
authors.forename: T
authors.initials: T
authors.lastname: Iwashita
authors.forename: K
authors.initials: K
authors.lastname: Nomoto
mesh_terms: D000595:Amino Acid Sequence; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003460:Crystallization; D006860:Hydrogen Bonding; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009479:Neuropeptides / Q000737:chemistry*; D011487:Protein Conformation; D014961:X-Ray Diffraction
chemical_list: D009479:Neuropeptides; C059927:achatin I