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
 
Function
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
Maps:       
Reactions:
      ESCHER  BiGG
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
Domain
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):
Legend
The Protein Feature View requires a browser that supports SVG (Scalable Vector Graphics). Mouse over tracks and labels for more information.
Data origin/color codes
The vertical color bar on the left side indicates data provenance.
Data in green originates from UniProtKB  
Variation data (sourced from UniProt) shows non-genetic variation from the ExPASy   and dbSNP   websites.
Data in yellow originates from Pfam  , by interacting with the HMMER3 web site  
Data in purple originates from Phosphosite  .
Data in orange originates from the SCOP   (version 1.75) and SCOPe   (version 2.04) classifications.
Data in grey has been calculated using BioJava  . Protein disorder predictions are based on JRONN (Troshin, P. and Barton, G. J. unpublished), a Java implementation of RONN  
  • Red: potentially disorderd region
  • Blue: probably ordered region.
Hydropathy has been calculated using a sliding window of 15 residues and summing up scores from standard hydrophobicity tables.
  • Red: hydrophobic
  • Blue: hydrophilic.
Data in lilac represent the genomic exon structure projected onto the UniProt sequence.
Data in blue originates from PDB
  • Secstruc: Secondary structure projected from representative PDB entries onto the UniProt sequence.
Sequence Mismatches It is now possible to see information about expression tags, cloning artifacts, and many other details related to sequence mismatches.
Icons represent a number of different sequence modifications that can be observed in PDB files. For example the 'T' icon T represents expression tags that have been added to the sequence. The 'E' icon E represents an engineered mutation. However, besides these two, there are many other icons. For more information about the meaning and exact position of a sequence modification, move the cursor over the icon.
Validation Track

For more details on the Validation Track (Structure Summary Page only) see the dedicated help page.

Data in red indicates combined ranges of Homology Models from the SWISS-MODEL Repository  
The PDB to UniProt mapping is based on the data provided by the EBI SIFTS project. See also Velankar et al., Nucleic Acids Research 33, D262-265 (2005).
Organism icons generated by flaticon.com under CC BY. The authors are: Freepik, Icons8, OCHA, Scott de Jonge.

For more details on the Protein Feature view see the dedicated help page.