Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.24.69 (botulinum neurotoxin)
 1,901 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Homogeneous beta-bungarotoxin, isolated from the venom of Bungarus multicinctus was radiolabelled with N-succinimidyl-[2.3-(3) H]propionate. Stable, di-propionylated material was obtained which was tritiated on both subunits and had a specific radioactivity of 102 Ci/mmol. 2. After separation from unlabelled toxin by isoelectric focussing, it was shown to exhibit significant biological activity in both the peripheral and central nervous systems but had negligible phospholipase A2 activity towards lecithin or cerebrocortical synaptosomes. 3. The labeled neurotoxin binds specifically to a single class of non-interacting sites of high affinity (Kd = 0.6 nM) on rat cerebral cortex synaptosomes; the content of sites is about 150 fmol/mg protein. This binding was inhibited by unlabelled beta-bungarotoxin with a potency which indicates that tritiation does not alter the affinity significantly. 4. The association of toxin with its binding component and its dissociation were monophasic; rate constants observed were 7.8 x 10(5) M-1 s-1 and 5.6 x 10(-4) s-1 at 37 C, respectively. 5. beta-Bungarotoxin whose phospholipase activity had been inactivated with p-bromophenacyl bromide inhibited to some extent the binding of tritiated toxin but with low efficacy. Taipoxin and phospholipase A2 from bee venom, but not Naja melanoleuca, inhibited the synaptosomal binding of toxin with low potencies in the presence, but not the absence, of Ca2+. 6. Toxin I, a single-chain protein from Dendroaspis polylepis known to potentiate transmitter release at chick neuromuscular junction, completely inhibited the binding of 3H-beta-bungarotoxin with a Ki of 0.07 nM; this explains its ability to antagonise the neuroparalytic action of beta-bungarotoxin. Other pure presynaptic neurotoxins, alpha-latrotoxin and botulinum neurotoxin failed to antagonise the observed binding; likewise tityustoxin, which is known to affect sodium channels, had no effect on 3H-beta-bungarotoxin binding. 7. Trypsinization of synaptosomes completely destroyed the binding activity, suggesting that the binding component is a protein; the functional role of the latter is discussed in relation to the specificity of toxin binding.
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PMID:Preparation of neurotoxic 3H-beta-bungarotoxin: demonstration of saturable binding to brain synapses and its inhibition by toxin I. 717 9

The molecular mechanisms of depolarization-induced calcium-dependent acetylcholine (ACh) release and its inhibition by botulinum neurotoxin type A (BoTx) are not clear. We studied these mechanisms in an in vitro cholinergic neuronal pheochromocytoma PC12 cell line model. Cultured monolayer PC12 cells were differentiated by treatment with 50 ng/ml nerve growth factor (NGF) for 4 days to enhance cellular ACh synthesis and release. Stimulation of these cells with high K+ (80 mM) in the perfusion medium caused a marked increase (three to four times) in [3H]ACh release in a Ca(2+)-dependent manner. K(+)-stimulated [3H]ACh release was totally inhibited by pretreatment of cells with BoTx (2 nM) for 2 h. High K+ also stimulated the release of arachidonic acid ([3H]AA) from the cell membrane, which was inhibited by BoTx (2 nM). Addition of phospholipase A2 (PLA2) inhibitors (quinacrine, 4-bromophenacyl bromide, manoalide) to the perfusion medium inhibited K(+)-stimulated [3H]ACh and [3H]AA release in a dose-dependent manner. Inclusion of exogenous AA, the PLA2 activator melittin, or PLA2 itself prevented the effect of BoTx. These results demonstrate that in NGF-differentiated PC12 cells, AA release is associated with ACh release, BoTx inhibits both processes, and increased AA can protect against BoTx.
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PMID:Botulinum toxin inhibits arachidonic acid release associated with acetylcholine release from PC12 cells. 849 67

Clostridium botulinum produces the potent botulinum neurotoxin, the causative agent of botulism. Based on distinctive physiological traits, strains of C. botulinum can be divided into four groups: however, only groups I and II are associated with human illness. Alignment of the flaA gene sequences from 40 group I and 40 group II strains identified a single BsrG1 restriction cut site that was present at base pair 283 in all group II flaA sequences and was not found in any group I sequence. The flaA gene was amplified by rapid colony PCR from 22 group I strains and 18 group II strains and digested with BsrGI restriction enzyme. Standard agarose gel electrophoresis with ethidium bromide staining showed two fragments, following restriction digestion of group II flaA gene amplicons with BsrGI, but only a single band of uncut flaA from group I strains. Combining rapid colony PCR with BsrGI restriction digest of the flaA gene at 60 degrees C is a significant improvement over current methods, such as meat digestion or amplified fragment length polymorphism, as a strain can be identified as either group I or group II in under 5 h when starting with a visible plated C. botulinum colony.
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PMID:A unique restriction site in the flaA gene allows rapid differentiation of group I and group II Clostridium botulinum strains by PCR-restriction fragment length polymorphism analysis. 1790 93