Botulinum neurotoxin type C1 - P18640 (BXC1_CLOBO)


Protein Feature View of PDB entries mapped to a UniProtKB sequence  

  • Number of PDB entries for P18640: 5
Botulinum neurotoxin type C: 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:16252491, PubMed:7901002, PubMed:8611567). Is unique among characterized BoNTs in having 2 substrates, syntaxin (STX) and SNAP25 (PubMed:7901002, PubMed:7737992, PubMed:8611567, PubMed:9886085, PubMed:17718519). Precursor of botulinum neurotoxin C which unlike most BoNTs seems not to have a proteinaceous coreceptor, and instead recognizes 2 different complex polysialylated gangliosides found on neural tissue probably found in synaptic vesicles (PubMed:21483489, PubMed:23027864). 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 heavy chain (HC) forms pores that allows the light chain (LC) to translocate into the cytosol (By similarity). 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 (By similarity). In vitro the whole toxin only has protease activity after reduction (PubMed:8611567). Electrical stimulation increases uptake of toxin, presumably by transiently exposing a receptor usually found in eukaryotic target synaptic vesicles (PubMed:19650874). Forms ion-conducting channels at around pH 6.1 (PubMed:2424493). Requires complex eukaryotic host polysialogangliosides for full neurotoxicity (PubMed:19650874, PubMed:21483489). Synaptic vesicle glycoproteins (SV2) do not seem to act as its receptor (PubMed:21483489). 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 a heavy chain (HC) (PubMed:16252491). The LC has the proteolytic/pharmacological activity (PubMed:7901002, PubMed:7737992, PubMed:8611567). The N- and C-terminal of the HC mediate channel formation and toxin binding, respectively. Can also be purified in complex with a non-toxic component that is larger than the HC (PubMed:16252491). UniProt
Botulinum neurotoxin C 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). The N-terminus of the TD wraps an extended belt around the perimeter of the LC, protecting Zn(2+) in the active site and may be a pseudosubstrate inhibitor which serves as an intramolecular chaperone for the LC prior to its translocation into the host cytosol. The RBD binds transiently exposed coreceptors on the host presynaptic cell membrane (By similarity). Binds phosphoinositides, which might play a role in membrane-binding (PubMed:22120109). UniProt
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