Botulinum neurotoxin type A - P0DPI0 (BXA1_CLOBO)


Protein Feature View of PDB entries mapped to a UniProtKB sequence  

  • Number of PDB entries for P0DPI0: 62
Botulinum neurotoxin type A: Botulinum toxin causes flaccid paralysis by inhibiting neurotransmitter (acetylcholine) release from the presynaptic membranes of nerve terminals of the eukaryotic host skeletal and autonomic nervous system, with frequent heart or respiratory failure (PubMed:15394302, PubMed:7578132). Precursor of botulinum neurotoxin A which has 2 coreceptors; complex polysialylated gangliosides found on neural tissue and specific membrane-anchored proteins of synaptic vesicles. Receptor proteins are exposed on host presynaptic cell membrane during neurotransmitter release, when the toxin heavy chain (HC) binds to them. Upon synaptic vesicle recycling the toxin is taken up via the endocytic pathway. When the pH of the toxin-containing endosome drops a structural rearrangement occurs so that the N-terminus of the HC forms pores that allows the light chain (LC) to translocate into the cytosol (PubMed:17666397, PubMed:19096517). Once in the cytosol the disulfide bond linking the 2 subunits is reduced and LC cleaves its target protein on synaptic vesicles, preventing their fusion with the cytoplasmic membrane and thus neurotransmitter release. Toxin activity requires polysialylated gangliosides; GT1b supports activity better than GD1a (PubMed:12089155). Binds to host peripheral neuronal presynaptic membranes via the synaptic vesicle glycoproteins SV2A, SV2B and SV2C (PubMed:16543415). It binds directly to the largest lumenal (intravesicular) loop of SV2A, SV2B and SV2C that is transiently exposed outside of cells during exocytosis; gangliosides enhance binding (PubMed:16543415, PubMed:16545378, PubMed:18815274). Recognizes an N-linked glycan on SV2 proteins (PubMed:18815274, PubMed:27294781). May also use FGFR3 as a receptor (PubMed:23696738). Toxin uptake into neural cells requires stimulation (incubation with K(+) to stimulate receptor exposure) to be internalized by receptor-mediated endocytosis (PubMed:16543415, PubMed:19650874, PubMed:21632541, PubMed:21832053). Subsequently the toxin colocalizes with its receptor in host cells (PubMed:16543415, PubMed:19650874). Toxin uptake can be blocked by the appropriate SV2 protein fragments in cell culture (PubMed:16543415). UniProt
Catalytic Activity
Limited hydrolysis of proteins of the neuroexocytosis apparatus, synaptobrevins, SNAP25 or syntaxin. No detected action on small molecule substrates. UniProt
Pathway Maps
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Subunit Structure
Heterodimer; disulfide-linked heterodimer of a light chain (LC) and heavy chain (HC) (PubMed:7578132). Interacts with glycosylated host synaptic vesicle glycoproteins SV2A, SV2B and SV2C which serve as coreceptors (PubMed:16543415, PubMed:18815274, PubMed:19650874, PubMed:24240280, PubMed:27313224). Glycosylation of 'Asn-559' in SV2C contributes a 12-fold increase in affinity to this interaction (PubMed:27313224). Depolarization of target tissue with high levels of K(+) leads to greater levels of receptor exposure (PubMed:16543415). In vitro addition of gangliosides increases SV2-toxin interaction (PubMed:16543415). Forms a highly interlocked heterodimer with NTNHA at pH 6.0 but not at pH 7.5 called the minimally functional progenitor toxin complex (M-PTC) (PubMed:22363010). The PTC is thought to protect toxin in the host acidic gastrointestinal tract, facilitate transcytosis across the intestinal barrier and release at neutral pH as is found in the bloodstream (PubMed:22363010). UniProt
Botulinum neurotoxin A heavy chain: Has 3 functional domains; the translocation domain (TD) and the receptor-binding domain (RBD) which is further subdivided into N- and C-terminal domains (N-RBD and C-RBD). Upon trypsin digestion the isolated TD forms channels in bilayers when the cis side is acidic/oxidizing and the trans side is pH 7.0/reducing (PubMed:2446925, PubMed:17666397, PubMed:19096517). The RBD rotates 140 degrees around the TD in the presence of NTNHA (PubMed:22363010). The 3 major domains each serve as a chaperone for the other 2 to ensure they act only in the correct host cell context (PubMed:19096517). In BoNT/A structures the LC is separated from the RBD by the TD; the belt wraps around the perimeter of the LC, protecting Zn(2+) in the active site (PubMed:18032388, PubMed:19351593, PubMed:22363010). The belt region (449-545) may be a pseudosubstrate inhibitor which serves as an intramolecular chaperone for the LC prior to its translocation into the host cytosol (PubMed:17907800). UniProt
  • Other Gene names: botA, atx, bonT
This protein in other organisms (by gene name):
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