title: Crystallization and preliminary X-ray analysis of bucain, a novel toxin from the Malayan krait Bungarus candidus.
abstract: Bucain is a three-finger toxin, structurally homologous to snake-venom muscarinic toxins, from the venom of the Malayan krait Bungarus candidus. These proteins have molecular masses of approximately 6000-8000 Da and encompass the potent curaremimetic neurotoxins which confer lethality to Elapidae and Hydrophidae venoms. Bucain was crystallized in two crystal forms by the hanging-drop vapour-diffusion technique in 0.1 M sodium citrate pH 5.6, 15% PEG 4000 and 0.15 M ammonium acetate. Form I crystals belong to the monoclinic system space group C2, with unit-cell parameters a = 93.73, b = 49.02, c = 74.09 A, beta = 111.32 degrees, and diffract to a nominal resolution of 1.61 A. Form II crystals also belong to the space group C2, with unit-cell parameters a = 165.04, b = 49.44, c = 127.60 A, beta = 125.55 degrees, and diffract to a nominal resolution of 2.78 A. The self-rotation function indicates the presence of four and eight molecules in the crystallographic asymmetric unit of the form I and form II crystals, respectively. Attempts to solve these structures by molecular-replacement methods have not been successful and a heavy-atom derivative search has been initiated.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017838:Bungarus; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D003460:Crystallization; D018360:Crystallography, X-Ray / Q000379:methods; D004546:Elapid Venoms / Q000737:chemistry* / Q000302:isolation & purification / Q000633:toxicity*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014118:Toxins, Biological / Q000737:chemistry* / Q000302:isolation & purification / Q000633:toxicity*
chemical_list: D004546:Elapid Venoms; D014118:Toxins, Biological; C472824:bucain