Botulinum neurotoxin type G

UniProtKB accession:  Q60393

Grouped By:  Matching UniProtKB accession

UniProtKB description:  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:15123599). Precursor of botulinum neurotoxin G which has 2 coreceptors; complex polysialylated gangliosides found on neural tissue and specific membrane-anchored proteins found in synaptic vesicles (PubMed:15123599). 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. 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). Binds to host peripheral neuronal presynaptic membranes via synaptotagmins 1 and 2 (SYT1 and SYT2) (PubMed:15123599). Toxin binds to the membrane proximal extra-cytoplasmic region of SYT1 and SYT2 that is transiently exposed outside of cells during exocytosis; exogenous gangliosides do not enhance binding and subsequent uptake of toxin into host cells (PubMed:15123599). Toxin activity can be blocked by the appropriate synaptotagmin protein fragments in cell culture (PubMed:15123599).