Structure and action of heteronemertine polypeptide toxins Binding of cerebratulus lacteus toxin B-IV to axon membrane vesicles |
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Authors: | Gregory P. Toth Kenneth M. Blumenthal |
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Affiliation: | Department of Biological Chemistry, University of Cincinnati College of Medicine, Cincinnati, OH 45267 U.S.A. |
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Abstract: | The binding of the crustacean selective protein neurotoxin, toxin B-IV, from the nemertine Cerebratulus lacteus to lobster axonal vesicles has been studied. A highly radioactive, pharmacologically active derivative of toxin B-IV has been prepared by reaction with Bolton-Hunter reagent. Saturation binding and competition of 125I-labeled toxin B-IV by native toxin B-IV have shown specific binding of 125I-labeled toxin B-IV to a single class of binding sites with a dissociation constant of 5–20 nM and a binding site capacity, corrected for vesicle sidedness, of 6–9 pmol per mg membrane protein. This compares to a value of 3.8 pmol [3H]saxitoxin bound per mg in the same tissue. Analysis of the kinetics of toxin B-IV association () and dissociation () shows a nearly identical of about 3 nM. There is no competition of toxin B-IV binding by purified toxin from Leiurus quinquestriatus venom while Centruroides sculpturatus Ewing toxin I appears to cause a small enhancement of toxin B-IV binding. |
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Keywords: | Neurotoxin Membrane-toxin interaction Toxin B-IV (Axon membrane) Hepes PMSF phenylmethylsulfonyl fluoride |
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