更新于:2024-11-01

BTX

基本信息

别名
BoNT、肉毒杆菌毒素
简介
Responsible for host epithelial cell transcytosis, host nerve cell targeting and translocation of light chain (LC) into host cytosol. Composed of 3 subdomains; the translocation domain (TD), and N-terminus and C-terminus of the receptor-binding domain (RBD). The N-terminus of the TD wraps an extended belt around the perimeter of the LC; it does not seem to protect the active site, but might prevent premature LC dissociation from the translocation channel and protect toxin prior to translocation (PubMed:10932256, PubMed:17167418). Has 2 coreceptors; complex gangliosides found primarily on neural tissue and host synaptotagmin-1 and -2 (SYT1 and SYT2) which bind simultaneously to adjacent but separate sites at the tip of the HC (PubMed:8144634, PubMed:17185412, PubMed:17167421, PubMed:17167418, PubMed:23807078). HC alone partially prevents uptake of whole toxin by neural cells, and delays paralysis onset by 160% (PubMed:10413679). Binding probably positions the TD for integration into the synaptic vesicle membrane (PubMed:17167418, PubMed:23807078). The HC forms channels at low pH that mediate transport of the light chain (LC) from the endocytic vesicle to the cytosol (PubMed:3856850). Binds gangliosides GD1b and GT1b (PubMed:10413679, PubMed:14731268). Gangliosides are not only a coreceptor, but also required for uptake into nerve cells (PubMed:21925111, PubMed:17167418). HC alone binds to host receptor proteins SYT1 and SYT2 (PubMed:14504267, PubMed:15123599, PubMed:17185412, PubMed:19650874). Interaction with SYT1 protein does not require SYT1 glycosylation (PubMed:19476346). The HC C-terminus (approximately residues 1079-1291) interacts with host SYT2 (PubMed:15123599, PubMed:17167421, PubMed:17167418, PubMed:23807078). Has higher affinity for SYT2 than SYT1 (PubMed:17185412, PubMed:17167421). Significantly decreases uptake and toxicity of whole BoNT/B and BoNT/G (PubMed:19650874). 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. Precursor of botulinum neurotoxin B which has 2 coreceptors; complex polysialylated gangliosides found on neural tissue and specific membrane-anchored proteins found in synaptic vesicles (PubMed:17185412, PubMed:17167421, PubMed:17167418, PubMed:23807078). Receptor proteins are exposed on host presynaptic cell membrane during neurotransmitter release, when the toxin heavy chain (HC) binds to them (PubMed:14504267). Upon synaptic vesicle recycling the toxin is taken up via the endocytic pathway (PubMed:14504267). 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:3856850). 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. Binds to host peripheral neuronal presynaptic membranes via synaptotagmins 1 and 2 (SYT1 and SYT2) (PubMed:8144634, PubMed:14504267). Toxin binds to the membrane proximal extra-cytoplasmic region of host SYT1 and SYT2 that is transiently exposed outside of cells during exocytosis; exogenous gangliosides enhance binding and subsequent uptake of toxin into host cells (PubMed:14504267, PubMed:15123599). Toxin uptake into neural cells requires stimulation (incubation with K(+) to stimulate SYT protein receptor exposure); subsequently the toxin colocalizes with its receptor in host cells with a concomitant decrease in target protein (synaptobrevin-2/VAMP2) immunoreactivity (PubMed:14504267). Toxin uptake can be blocked by the appropriate synaptotagmin protein fragments and gangliosides in cell culture and in mice (PubMed:14504267, PubMed:15123599). BoNT/B is a 'coincidence detector'; it requires simultaneous binding to coreceptor GT1b and low pH to transform into a membrane-bound, oligomeric channel (PubMed:21925111, PubMed:22720883). Whole toxin only has protease activity after reduction which releases LC (PubMed:1331807, PubMed:7803399). Has proteolytic activity (PubMed:1331807). After translocation into the eukaryotic host cytosol, inhibits neurotransmitter release by acting as a zinc endopeptidase that cleaves the '76-Gln-|-Phe-77' bond of synaptobrevin-2/VAMP2, blocking neurotransmitter release (PubMed:1331807, PubMed:7803399). In vitro the LC only has protease activity after reduction (PubMed:1331807, PubMed:7803399).

分析

对领域进行一次全面的分析。
对领域进行一次全面的分析。
来和芽仔聊天吧
立即开始免费试用!
智慧芽新药情报库是智慧芽专为生命科学人士构建的基于AI的创新药情报平台,助您全方位提升您的研发与决策效率。
立即开始数据试用!
智慧芽新药库数据也通过智慧芽数据服务平台,以API或者数据包形式对外开放,助您更加充分利用智慧芽新药情报信息。
生物序列数据库
生物药研发创新
免费使用
化学结构数据库
小分子化药研发创新
免费使用