![]() ![]() Seven serotypes of BoNT have been identified (termed A-G), which cleave different SNARE proteins at distinct residues: BoNT/A and BoNT/E cleave SNAP-25 (synaptosome-associated protein of 25 kDa), while BoNT/B, /D, /F and /G cleave VAMP-2 (vesicle associated membrane protein), and BoNT/C cleaves both SNAP-25 and syntaxin-1. #X V AMP PATCH EDITOR DRIVERS#The LC is a zinc-dependent metalloprotease that specifically cleaves soluble N-Ethylmaleimide-sensitive factor attachment receptor (SNARE) proteins–the drivers of synaptic vesicle fusion with the plasma membrane. The HC consists of two sub-domains: H C, responsible for neuronal cell binding and H N, a translocation domain which functions to deliver the LC from internalized endosomal compartments into the cytosol. In order to augment the efficacy of BoNT/B in humans, strategies other than enhancing light chain activity may need to be considered.īotulinum neurotoxins (BoNTs) are 150 kDa modular proteins consisting of two sub-units: an N-terminal light chain (LC) domain of 50 kDa and a heavy chain (HC) domain of 100 kDa, which are linked by a disulphide bond. The lack of translation from the enhanced BoNT/B1 (S201P) catalytic activity to potency in complex biological systems suggests that the catalytic step is not the rate-limiting factor for BoNT/B to reach maximum efficacy. Finally, no differences between rBoNT/B1 and rBoNT/B1 (S201P) were observed in an in vivo digit abduction score (DAS) assay in C57BL/6N mice, either in efficacy or safety parameters. Similarly in ex vivo tissue preparations rBoNT/B1 (S201P) was not significantly more potent than rBoNT/B1 at inhibiting either diaphragm or detrusor (bladder) muscle activity in C57BL/6N and CD1 mice. However, despite the enhanced catalytic activity of rBoNT/B1 (S201P), there was no significant difference in potency between the two molecules in any of the in vitro cell-based assays, using either rodent spinal cord neurons or cortical neurons. In the cell-free assay, which measured light-chain activity alone, rBoNT/B1 (S201P) cleaved VAMP-2 and VAMP-1 substrate with an activity 3–4-fold higher than rBoNT/B1. ![]() We have compared the activity of these two molecules along with a native BoNT/B1 in biochemical cell-free assays and in several biological systems. coli–one wild type (rBoNT/B1) and one incorporating the S201P mutation (rBoNT/B1 (S201P)). In this study, we have produced two full-length recombinant BoNT/B toxins in E. Recently, a mutation in the light chain of BoNT/B (S201P) was described that increases the catalytic activity of the isolated BoNT/B light chain in biochemical assays. Advances in our understanding of BoNT/B mechanism of action have afforded the opportunity to make rational modifications to the toxin aimed at increasing its activity. Higher doses of BoNT/B are required to reach an efficacy similar to that of products containing BoNT/A. ![]() Serotypes A and B are available as marketed products. Mark Elliott, Data curation, Formal analysis, Investigation, Methodology, Supervision, Writing – original draft, Writing – review & editing, # 1, * Jacquie Maignel, Data curation, Formal analysis, Investigation, Methodology, Writing – review & editing, # 2 Sai Man Liu, Data curation, Formal analysis, Investigation, Methodology, Writing – review & editing, # 1 Christine Favre-Guilmard, Data curation, Formal analysis, Investigation, Writing – review & editing, # 2 Imran Mir, Formal analysis, Investigation, 1, ‡ Paul Farrow, Data curation, Formal analysis, Investigation, Methodology, 1, ‡ Fraser Hornby, Data curation, Formal analysis, Investigation, Methodology, Writing – review & editing, 1, ‡ Sandra Marlin, Investigation, 1, ‡ Shilpa Palan, Data curation, Formal analysis, Supervision, # 1 Matthew Beard, Conceptualization, Project administration, Writing – review & editing, # 1 and Johannes Krupp, Conceptualization, Project administration, Writing – original draft, Writing – review & editing # 2īotulinum neurotoxins (BoNTs) are used extensively as therapeutic agents. ![]()
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