Botulinum neurotoxin type E

UniProtKB accession:  Q00496

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UniProtKB description:  Botulinum toxin causes flaccid paralysis by inhibiting neurotransmitter (acetylcholine) release from the presynaptic membranes of nerve terminals of eukaryotic host skeletal and autonomic nervous system, with frequent heart or respiratory failure. Precursor of botulinum neurotoxin E which has 2 coreceptors; complex polysialylated gangliosides found on neural tissue and specific membrane-anchored proteins found in synaptic vesicles. Receptor proteins are exposed on host presynaptic cell membrane during neurotransmitter release, when the toxin heavy chain (HC) binds to them (PubMed:19476346, PubMed:19650874). 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:22720883). 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). Electrical stimulation increases uptake of toxin, probably by transiently exposing a receptor found in eukaryotic target synaptic vesicles (PubMed:19476346, PubMed:19650874). Uses the large lumenal domain of synaptic vesicle glycoproteins 2A and 2B (SV2A and SV2B) but not SV2C as receptor; an N-linked glycan of SV2 is essential for receptor function (PubMed:18815274, PubMed:19476346). Host cell gangliosides are also required for neurotoxin uptake and full toxicity (PubMed:18815274, PubMed:19650874). BoNT/E is a 'coincidence detector'; it requires simultaneous binding to coreceptor GT1b and low pH to transform into a membrane-bound, oligomeric channel (PubMed:22720883). Requires trypsinization and reduction before it can be used in assays in vitro (PubMed:8294407).