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)

Clostridium botulinum neurotoxin acts on nerve endings to block acetylcholine release. Binding of the neurotoxin to a membrane receptor through its heavy chain is the first essential step in its mode of toxin action. Type E botulinum neurotoxin (BoNT/E) or type A botulinum neurotoxin (BoNT/A) receptor was purified from rat brain synaptosomes employing a neurotoxin affinity column chromatography. The protein fraction eluted from the affinity column with 0.5 M NaCl contained a 57 kDa protein as a major eluant. Immunoblotting the eluant with anti-synaptotagmin antibodies revealed that the 57 kDa protein was synaptotagmin I. Rat synaptotagmin I has been suggested as the receptor for BoNT/B (Nishiki et al., J. Biol. Chem. 269, 10498-10503, 1994) in rat brain. In this study, binding of BoNT/A and BoNT/E to synaptotagmin I was studied by a microtiter plate-based method. Binding of synaptotagmin I to BoNT/A coated on the plate was competitively reduced upon preincubation of the proteins with BoNT/E, suggesting a competitive binding of BoNT/A and BoNT/E to the receptor. Taken together, these results suggest that the same receptor protein binds to all three BoNT serotypes tested.
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PMID:Isolation of synaptotagmin as a receptor for types A and E botulinum neurotoxin and analysis of their comparative binding using a new microtiter plate assay. 978 60

We investigated the effect of synaptotagmin I on membrane fusion mediated by neuronal SNARE proteins, SNAP-25, syntaxin, and synaptobrevin, which were reconstituted into vesicles. In the presence of Ca2+, the cytoplasmic domain of synaptotagmin I (syt) strongly stimulated membrane fusion when synaptobrevin densities were similar to those found in native synaptic vesicles. The Ca2+ dependence of syt-stimulated fusion was modulated by changes in lipid composition of the vesicles and by a truncation that mimics cleavage of SNAP-25 by botulinum neurotoxin A. Stimulation of fusion was abolished by disrupting the Ca2+-binding activity, or by severing the tandem C2 domains, of syt. Thus, syt and SNAREs are likely to represent the minimal protein complement for Ca2+-triggered exocytosis.
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PMID:Reconstitution of Ca2+-regulated membrane fusion by synaptotagmin and SNAREs. 1504 54

Botulinum neurotoxins (BoNTs) are produced by Clostridium botulinum and cause the neuroparalytic syndrome of botulism. With a lethal dose of 1 ng kg(-1), they pose a biological hazard to humans and a serious potential bioweapon threat. BoNTs bind with high specificity at neuromuscular junctions and they impair exocytosis of synaptic vesicles containing acetylcholine through specific proteolysis of SNAREs (soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptors), which constitute part of the synaptic vesicle fusion machinery. The molecular details of the toxin-cell recognition have been elusive. Here we report the structure of a BoNT in complex with its protein receptor: the receptor-binding domain of botulinum neurotoxin serotype B (BoNT/B) bound to the luminal domain of synaptotagmin II, determined at 2.15 A resolution. On binding, a helix is induced in the luminal domain which binds to a saddle-shaped crevice on a distal tip of BoNT/B. This crevice is adjacent to the non-overlapping ganglioside-binding site of BoNT/B. Synaptotagmin II interacts with BoNT/B with nanomolar affinity, at both neutral and acidic endosomal pH. Biochemical and neuronal ex vivo studies of structure-based mutations indicate high specificity and affinity of the interaction, and high selectivity of BoNT/B among synaptotagmin I and II isoforms. Synergistic binding of both synaptotagmin and ganglioside imposes geometric restrictions on the initiation of BoNT/B translocation after endocytosis. Our results provide the basis for the rational development of preventive vaccines or inhibitors against these neurotoxins.
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PMID:Botulinum neurotoxin B recognizes its protein receptor with high affinity and specificity. 1716 19

Botulinum neurotoxin causes rapid flaccid paralysis through the inhibition of acetylcholine release at the neuromuscular junction. The seven BoNT serotypes (A-G) have been proposed to bind motor neurons via ganglioside-protein dual receptors. To date, the structure-function properties of BoNT/F host receptor interactions have not been resolved. Here, we report the crystal structures of the receptor binding domains (HCR) of BoNT/A and BoNT/F and the characterization of the dual receptors for BoNT/F. The overall polypeptide fold of HCR/A is essentially identical to the receptor binding domain of the BoNT/A holotoxin, and the structure of HCR/F is very similar to that of HCR/A, except for two regions implicated in neuronal binding. Solid phase array analysis identified two HCR/F binding glycans: ganglioside GD1a and oligosaccharides containing an N-acetyllactosamine core. Using affinity chromatography, HCR/F bound native synaptic vesicle glycoproteins as part of a protein complex. Deglycosylation of glycoproteins using alpha(1-3,4)-fucosidase, endo-beta-galactosidase, and PNGase F disrupted the interaction with HCR/F, while the binding of HCR/B to its cognate receptor, synaptotagmin I, was unaffected. These data indicate that the HCR/F binds synaptic vesicle glycoproteins through the keratan sulfate moiety of SV2. The interaction of HCR/F with gangliosides was also investigated. HCR/F bound specifically to gangliosides that contain alpha2,3-linked sialic acid on the terminal galactose of a neutral saccharide core (binding order GT1b = GD1a >> GM3; no binding to GD1b and GM1a). Mutations within the putative ganglioside binding pocket of HCR/F decreased binding to gangliosides, synaptic vesicle protein complexes, and primary rat hippocampal neurons. Thus, BoNT/F neuronal discrimination involves the recognition of ganglioside and protein (glycosylated SV2) carbohydrate moieties, providing a structural basis for the high affinity and specificity of BoNT/F for neurons.
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PMID:Glycosylated SV2 and gangliosides as dual receptors for botulinum neurotoxin serotype F. 1947 46