Structure- and Substrate-based Inhibitor Design for Clostridium botulinum Neurotoxin Serotype A (original) (raw)
Related papers
Expression and Purification of Clostridium botulinum Type B Light Chain
Protein Expression and Purification
A full-length synthetic gene encoding the light chain of botulinum neurotoxin serotype B, approximately 50 kDa (BoNT/B LC), has been cloned into a bacterial expression vector pET24a+. BoNT/B LC was expressed in Escherichia coli BL21.DE3.pLysS and isolated from the soluble fraction. The resultant protein was puriWed to homogeneity by cation chromatography and was determined to be >98% pure as assessed by SDS-polyacrylamide gel stained with SilverXpress and analyzed by densitometry. Mass spectroscopic analysis indicated the protein to be 50.8 kDa, which equaled the theoretically expected mass. N-terminal sequencing of the puriWed protein showed the sequence corresponded to the known reported sequence. The recombinant BoNT/B light chain was found to be highly stable, catalytically active, and has been used to prepare antisera that neutralizes against BoNT/B challenge. Characterization of the protein including pH, temperature, and the stability of the protein in the presence or absence of zinc is described within. The inXuence of pH diVerences, buVer, and added zinc on secondary and tertiary structure of BoNT/B light chain was analyzed by circular dichroism and tryptophan Xuorescence measurements. Optimal conditions for obtaining maximum metalloprotease activity and stabilizing the protein for long term storage were determined. We further analyzed the thermal denaturation of BoNT/B LC as a function of temperature to probe the pH and added zinc eVects on light chain stability. The synthetic BoNT/B LC has been found to be highly active on its substrate (vesicle associated membrane protein-2) and, therefore, can serve as a useful reagent for BoNT/B research. Published by Elsevier Inc.
Cloning of Binding Domain of Clostridium botulinum Toxin Type A in Escherichia coli
Neurotoxin of Clostridium botulinum is one of the most potent known toxins in nature, which can cause an often fatal food poisoning. However, recently the use of binding domain of the toxin has also been proposed as a candidate vaccine. In this study coding region for this domain was amplified from genomic DNA of Clostridium botulinum type A using a pair of primers containing BamHI and HindIII. The amplified 1.3kb fragment corresponding to the gene of interest was cloned in pUC18 after verification with different restriction enzymes. The construct was then transformed into competent Escherichia coli DH5α and the recombinant clone was selected on plates containing ampicillin. The plasmid purified from these clones was used for sequencing by dideoxy chain termination method. The sequence thus obtained was verified by comparison with published sequence, which showed the authencity of the PCR product. This fragment was subcloned in an IPTG inducible expression vector pQE30 using E.coli M15 as a host and expression was analyzed by RT-PCR.
High level expression of recombinant BoNT/A-Hc by high cell density cultivation of Escherichia coli
Bioprocess and Biosystems Engineering, 2012
The carboxylic domain of the Clostridium botulinum neurotoxin heavy chain (BoNT/A-HC), which has been reported as a vaccine candidate, contains the principle protective antigenic determinants. In this study, the high level expression of the BoNT/A-Hc was achieved by high cell density cultivation of recombinant Escherichia coli in a 2-l batch stirred-tank bioreactor. In order to maximize protein expression, post-induction time and IPTG inducer concentration were optimized by the Taguchi statistical design method. Results showed that the middle of the logarithmic phase and an IPTG concentration of 1 mM presented the optimum conditions for the maximum expression of BoNT/A-HC. High cell density cultivation was subsequently carried out as an effective strategy for the high level expression of recombinant BoNT/A-Hc. Consequently, soluble BoNT/A-Hc was produced at the maximum level of 486 mg l -1 , at 3 h post-induction, which was approximately 9.3 and 7.8 times higher than the levels produced by the shake flask and batch culturing methods, respectively.
Protein Expression and Purification, 2000
A truncated but functional form of the botulinum neurotoxin A light chain (Tyr 9-Leu 415) has been cloned into the three bacterial expression vectors, pET 28, pET 30, and PGEX-2T, and produced as fusion proteins. This 406-amino-acid light chain was expressed with 1 six-histidine tag (LC-pET28), 2 six histidine tags and a Stag (LC-pET30), or a six-histidine tag and a glutathione S-transferase tag (LC-pGEX-2T). The three fusion proteins have been overexpressed in Escherichia coli, purified in a soluble form, and tested for protease activity. All three recombinant proteins were found to have similar enzymatic activity, comparable to the light chain purified from the whole toxin. The LC-pET30 protein was the most soluble and stable of the three fusion proteins, and it could be purified using a one-step affinity chromatography protocol. The purified protein was determined to be 98% pure as assessed by SDS-polyacrylamide gel. This protein has been crystallized and initial X-ray data show that the crystals diffract to 1.8 Å.
Protein Expression and Purification, 2006
A recombinant C-terminus heavy chain fragment from botulinum neurotoxin serotype E (BoNT/E) is proposed as a vaccine against the serotype E neurotoxin. This fragment, rBoNTE(H c), was produced intracellular in Pichia pastoris GS115 by a three-step fermentation process, i.e., glycerol batch phase and a glycerol fed-batch phase to achieve high cell densities, followed by a methanol fed-batch induction phase. The rBoNTE(H c) protein was puriWed from the soluble fraction of cell lysates using three ion-exchange chromatography steps (SP Sepharose Fast Flow, Q Sepharose Fast Flow, Sp Sepharose High Performance) and polished with a hydrophobic charge induction chromatography step (MEP HyperCel). Method development at the bench scale was achieved using 7-380 mL columns and the process was performed at the pilot scale using 0.5-3.1 L columns in preparation for technology transfer to cGMP manufacturing. The puriWcation process resulted in greater than 98% pure rBoNTE(H c) based on HPLC and yielded up to 1.01 g of rBoNTE(H c)/kg cells at the bench scale and 580 mg vaccine/kg cells at the pilot scale. N-terminal sequencing showed that the puriWed rBoNTE(H c) N-terminus is intact and was found to protect mice against a challenge of 1000 mouse intraperitoneal LD 50 's of BoNT/E.
Microbiology, 1997
Bacterial neurotoxins are now being used routinely for the treatment of neuromuscular conditions. Alternative assays to replace or to complement in vivo bioassay methods for assessment of the safety and potency of these botulinum neurotoxin-based therapeutic products are urgently needed. Advances made in understanding the mode of action of clostridial neurotoxins have provided the basis for the development of alternative mechanism-based assay methods. Thus, the identification of SNAP-25 (synaptosomal-associated protein of molecular mass 25 kDa) as the intracellular protein target which is selectively cleaved during poisoning by botulinum neurotoxin type A (BoNT/A) has enabled the development of a functional in vitro assay for this toxin. Using recombinant DNA methods, a segment of SNAP-25 (aa residues 134-206) spanning the toxin cleavage site was prepared as a fusion protein to the maltose-binding protein in Escherichia coli. The fusion protein was purified by affinity chromatograph...
The protein journal, 2017
Botulinum neurotoxins (BoNTs) are the most toxic proteins known to cause flaccid muscle paralysis as a result of inhibition of neurotransmitter release from peripheral cholinergic synapses. BoNT type A (BoNT/A) is a 150 kDa protein consisting of two major subunits: light chain (LC) and heavy chain (HC). The LC is required for the catalytic activity of neurotoxin, whereas the C and N terminal domains of the HC are required for cell binding, and translocation of LC across the endosome membranes, respectively. To better understand the structural and functional aspects of BoNT/A intoxication we report here the development of high yield Escherichia coli expression system (2-20-fold higher yield than the value reported in the literature) for the production of recombinant light chain-translocation domain (rLC-TD/A) module of BoNT/A which is catalytically active and translocation competent. The open reading frame of rLC-TD/A was PCR amplified from deactivated recombinant BoNT/A gene (a non-...
The Botulinum J., 2008
Botulinum Neurotoxin (BoNT) is responsible for botulism, a severe and often deadly disease. Light chain of BoNT behaves as endopeptidase, cleaving the SNARE proteins, and inhibits the neurotransmitter release. A double-mutant E224A/E262A full-length BoNT Type A was successfully cloned and expressed in E. coli. The purified protein lacks the endopeptidase activity involved in the toxic action, and is structurally compatible with the native BoNT/A. Thus this molecule not only can be used as a safe surrogate for study of BoNT, but also can be potentially used as an antidote against botulism, and as a vaccine candidate for botulism.
Protein Expression and Purification, 2002
Clostridium botulinum neurotoxin type A is a potently toxic protein of 150 kDa with specific endopeptidase activity for the SNARE protein SNAP-25. Proteolytic cleavage of BoNT/A with trypsin leads to removal of the C-terminal domain responsible for neuronal cell binding. Removal of this domain result in a catalytically active, non-cell-binding derivative termed LH N /A. We have developed a purification scheme to prepare LH N /A essentially free of contaminating BoNT/A. LH N /A prepared by this scheme retains full enzymatic activity, is stable in solution, and is of low toxicity as demonstrated in a mouse toxicity assay. In addition, LH N /A has minimal effect on release of neurotransmitter from a primary cell culture model. Both the mouse bioassay and in vitro release assay suggest BoNT/A is present at less than 1 in 10 6 molecules of LH N /A. This represents a significant improvement on previously reported figures for LH N /A, and also the light chain domain, previously purified from BoNT/A. To complement the preparation of LH N /A from holotoxin, DNA encoding LH N /A has been introduced into Escherichia coli to facilitate expression of recombinant product. Expression and purification parameters have been developed to enable isolation of soluble, stable endopeptidase with a toxicity profile enhanced on that of LH N /A purified from BoNT/A. The recombinant-derived material has been used to prepare antisera that neutralise a BoNT/A challenge. The production of essentially BoNT/A-free LH N /A by two different methods and the possibilities for exploitation are discussed.
Protein Science, 2012
The light chain of botulinum neurotoxin A (BoNT/A-LC) is a Zn-dependent protease that specifically cleaves SNAP25 of the SNARE complex, thereby impairing vesicle fusion and neurotransmitter release at neuromuscular junctions. The C-terminus of SNAP25 (residues 141-206) retains full activity for BoNT/A-LC-catalyzed cleavage at P1-P1' (Gln197-Arg198). Using the structure of a complex between the C-terminus of SNAP25 and BoNT/A-LC as a model to design SNAP25-derived pseudosubstrate inhibitors (SNAPIs) that prevent presentation of the scissile bond to the active site, we introduced multiple His residues to replace Ala-Asn-Gln-Arg (residues 195-198) at the substrate cleavage site, with the intent to identify possible side-chain interactions with the active site Zn. We also introduced multiple Gly residues between the P1-P1' residues to explore the spatial tolerance within the active-site cleft. Using a FRET substrate YsCsY, we compared a series of SNAPIs for inhibition of BoNT/A-LC. Among the SNAPIs tested, several known cleavage-resistant, single-point mutants of SNAP25 were poor inhibitors, with most of the mutants losing binding affinity. Replacement with His at the active site did not improve inhibition over wildtype substrate. In contrast, Gly-insertion mutants were not only resistant to cleavage, but also surprisingly showed enhanced affinity for BoNT/A-LC. Two of the Gly-insertion mutants exhibited 10-fold lower IC 50 values than the wildtype 66-mer SNAP25 peptide. Our findings illustrate a scenario, where the induced fit between enzyme and bound pseudosubstrate fails to produce the strain and distortion required for catalysis to proceed.