title: Crystal structure of deltakephalin: a delta-selective opioid peptide with a novel beta-bend-like conformation.
abstract: The solid-state structure of deltakephalin (Tyr-DThr-Gly-Phe-Leu-Thr) has been determined by single-crystal X-ray diffraction. Deltakephalin (DTLET) is a synthetic opioid peptide which differs from enkephalin in that a D-Thr has been substituted for Gly2 and a sixth residue, L-Thr, has been added. Clear colorless plates obtained using vapor diffusion and macro-seeding crystallization techniques were monoclinic; space group C2 with a = 27.389(5), b = 9.205(2), c = 16.788(2) A, beta = 98.87(2) degrees and V = 4181.4(14) A3. The asymmetric unit contained one molecule of DTLET and six molecules of water, giving a calculated density of 1.28 g cm-3. The crystal structure revealed that DTLET has a pseudo type I' beta-bend which is stabilized by an intramolecular side-chain to backbone hydrogen bond. This is the first reported observation of a pseudo beta-bend conformation in a solid-state structure of an enkephalin analog.
authors.affiliation: Laboratory for the Structure of Matter, Naval Research Laboratory, Washington, DC.
authors.forename: J L
authors.initials: JL
authors.lastname: Flippen-Anderson
authors.forename: J R
authors.initials: JR
authors.lastname: Deschamps
authors.forename: K B
authors.initials: KB
authors.lastname: Ward
authors.forename: C
authors.initials: C
authors.lastname: George
authors.forename: R
authors.initials: R
authors.lastname: Houghten
mesh_terms: D018360:Crystallography, X-Ray; D004745:Enkephalins / Q000737:chemistry; D006860:Hydrogen Bonding; D016018:Least-Squares Analysis; D009842:Oligopeptides / Q000737:chemistry* / Q000378:metabolism; D017433:Protein Structure, Secondary; D017465:Receptors, Opioid, delta / Q000819:agonists*; D014867:Water / Q000737:chemistry
chemical_list: D004745:Enkephalins; D009842:Oligopeptides; D017465:Receptors, Opioid, delta; D014867:Water; C037653:deltakephalin