The structure of agkistrodotoxin crystallized under basic conditions has been determined at 2.8 Angstrom resolution by the molecular-replacement technique and refined to a crystallographic R factor of 0.194 and a free...
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The structure of agkistrodotoxin crystallized under basic conditions has been determined at 2.8 Angstrom resolution by the molecular-replacement technique and refined to a crystallographic R factor of 0.194 and a free R factor of 0.260 with good stereochemistry. The molecular packing in the crystal differs from other PLA(2)s. The six molecules in the asymmetric unit form three dimers linked by Ca2+ ions in a near-perfect six-ligand octahedral coordinating system. Extensive intermolecular hydrophobic interactions occur at the interfacial recognition site of each neurotoxin molecule, which provides an insight into phospholipase A(2)-membrane interactions. This hydrophobic interaction-induced molecular association along the interfacial recognition site suggests a self-protection mechanism of agkistrodotoxin.
A new neurotoxin BmK M2, toxic to both mammals and insects, with the strongest toxicity in the BmK toxin series, has been purified from the Chinese scorpion Buthus martensii Karsch and crystallized with MPD at pH 7.5....
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A new neurotoxin BmK M2, toxic to both mammals and insects, with the strongest toxicity in the BmK toxin series, has been purified from the Chinese scorpion Buthus martensii Karsch and crystallized with MPD at pH 7.5. The crystals are orthorhombic, belonging to space group P2(1)2(1)2(1), with unit-cell parameters a = 36.64, b = 36.95, c = 37.23 Angstrom. The structure was solved by molecular replacement and refined to R = 0.186 for all reflections to a resolution of 1.76 Angstrom. The whole sequence (64 residues) of BmK M2 was determined by crystallographic analysis based on high-resolution data and the homologous model of BmK M8. The refined BmK M2 structure shows a non-proline cis peptide bond between Pro9 and His10 which enables the C-terminal segment to adopt a conformation different to that of the weak toxin BmK M8. Recently, a mutation analysis had suggested that both the tenth residue and the C-terminus play key roles in receptor binding. Therefore, these features may be related to the binding selectivity of the group III alpha-like toxins. The charge changes of residues 8, 10, 18, 28, 55 and 59 from neutral or negative to positive or neutral, which leads to a positive electrostatic potential surface, may be responsible for the high toxicity of BmK M2.
Scorpion neurotoxin Ts-gamma was isolated from Tityus serrulatus venom and purified to apparent homogeneity by ion-exchange HPLC. Crystals of the toxin were grown using polyethylene glycol 6000 as precipitant and were...
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Scorpion neurotoxin Ts-gamma was isolated from Tityus serrulatus venom and purified to apparent homogeneity by ion-exchange HPLC. Crystals of the toxin were grown using polyethylene glycol 6000 as precipitant and were found to belong to the monoclinic space group P2(1) with cell parameters a = 22.20, b = 36.90, c = 31.57 Angstrom, beta = 100.85 degrees. The crystals diffract beyond 1.73 Angstrom resolution at a synchrotron beamline, being notably stable during X-ray exposure. The structure has been solved by molecular replacement using the very high resolution structure of Sahara scorpion Androctonus australis Hector (PDB code 1AHO) as a search model.
Candoxin, a novel three-finger toxin from Bungarus candidus, is a reversible antagonist of muscle (alphabetagammadelta) but a poorly reversible antagonist of neuronal alpha7 nicotinic acetylcholine receptors. It has a...
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Candoxin, a novel three-finger toxin from Bungarus candidus, is a reversible antagonist of muscle (alphabetagammadelta) but a poorly reversible antagonist of neuronal alpha7 nicotinic acetylcholine receptors. It has a molecular weight of 7344 Da, with 66 amino-acid residues including ten half-cystines. The fifth disulfide bridge is located at the tip of loop I (Cys6-Cys11) instead of in loop II as found in other alpha-neurotoxins. Interestingly, candoxin lacks the segment cyclized by the fifth disulfide bridge at the tip of the middle loop of long-chain neurotoxins, which was reported to be critical for binding to alpha7 receptors. As a first step to determining its three-dimensional structure, candoxin was crystallized by the hanging-drop vapour-diffusion technique in conditions around 1.5 M sodium chloride, 10%(v/v) ethanol. The crystals formed belonged to the hexagonal system, space group P6(2)22, with unit-cell parameters a = 54.88, b = 54.88, c = 75.54 Angstrom, alpha = beta = 90, = 120degrees, and diffract to a resolution of 1.80 Angstrom. The crystallographic asymmetric unit contains one molecule of candoxin, with an estimated solvent content of 44.6%. Attempts to solve these structures by molecular-replacement methods have not been successful and a heavy-atom derivative search has been initiated.
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