botulinumexpression system

botulinumexpression system. A2 culture. N-terminal protein sequencing was also employed to specifically detect ORFX2. Results showed that all of the neurotoxin cluster proteins, except ORFX1, were expressed in the A2 culture. A BoNT/A2 toxin complex (TC) was purified which showed thatC. botulinumA2 created a medium-size (300-kDa) TC composed of BoNT/A2 and NTNH without any of the other OrfX cluster proteins. NTNH subtype-specific immunoreactivity was also discovered, allowing for the differentiation of subtypes based on cluster proteins associated with BoNT. Botulinum neurotoxins (BoNTs) produced byClostridium botulinumare the most potent toxins known in nature and are characterized as category A select agents since they are considered potential bioterrorism threats (3). BoNTs can be distinguished immunologically into seven serotypes by using homologous antitoxins, designated A to G. BoNT/A is usually of particular interest, since it is frequently implicated in cases of botulism and is a significant threat in bioterrorism (1,10). BoNT is usually a 150-kDa protein composed of a heavy chain (100 kDa) and a light chain (50 kDa) linked by a disulfide bond and noncovalent molecular interactions (24). The heavy chain (H) has two functional domains, a transmembrane domain name Piperidolate hydrochloride and a receptor binding domain name. The light chain (L) is usually a zinc-dependent protease which specifically cleaves one of the three solubleN-ethylmaleimide-sensitive factor attachment Rabbit Polyclonal to KAPCB protein receptors, Piperidolate hydrochloride resulting in the blockage of evoked acetylcholine release at the skeletal neuromuscular junction (8). Previous studies have found that thebontgenes of all strains ofC. botulinumand neurotoxigenic strains ofClostridium butyricumandClostridium baratiihave a set of genes located upstream of thebontandntnhgenes that are organized as gene clusters (5,7,23). The two known main types of clusters are (i) a hemagglutinin (ha) cluster and (ii) anorfXcluster with open reading frames (ORFs) of unknown functions. Thehacluster consists of genes encoding HA17, HA33, HA70, BotR, and NTNH. TheorfXcluster consists of genes encoding ORFX3, ORFX2, ORFX1, P47, P21, and NTNH. Previous studies show that BoNT/A subtypes possess either ahacluster or anorfXcluster associated with their expressedbontgene, depending on the subtype and strain (5,11,13-15,33). It has been shown that this BoNT complex can form stable toxin complexes (TCs) of various sizes, including LL-TC (900 kDa), L-TC (500 kDa), and M-TC (300 kDa) composed of numerous combinations of HA proteins, NTNH, and BoNT (19,21,23,29,31,34). M-TC contains BoNT and NTNH but has no HA proteins, whereas LL-TC and L-TC contain different ratios of the BoNT, NTNH, and HA proteins (21,22,29,34). The biological and structural functions of the complex proteins are not completely characterized, although it has been proposed that they serve the role of protecting BoNT from harsh conditions, including pH, salt, heat, and digestive enzymes, and that they aid BoNT translocation across the intestinal epithelial layer (2,6,17). A recent report indicated that this nontoxic proteins serve as adjuvants and contribute to the immunogenicity of BoNT/A (25). The production of botulinum TCs is known to vary with different serotypes and strains, medium composition, and Piperidolate hydrochloride culture conditions (21,24,31). The LL-TC Piperidolate hydrochloride has only been observed in proteolytic strains (group I). Serotype A to D strains produce M-TC and L-TC in their culture medium, while serotype E and F strains produce only M-TC (17,18). In 1986, a Japanese group isolated four HA-negativeC. botulinumstrains from infant botulism cases that produced only M-TC (300 kDa). They assigned the strains to subtype A2 (14,30). In 2004, our laboratory confirmed on a genomic level that this BoNT/A2 subtype contained theorfXcluster instead of thehacluster (12). Since then, more plans and combinations of neurotoxin gene clusters were characterized along with more BoNT subtypes (13,20,33). However, the function of theorfXgenes and the role of the presumptive protein products and their role in the TCs are still unknown, including whether ORFX proteins can form a TC with the expressed toxin analogous to thehacluster proteins. In this study, the BoNT/A2 TC was purified from a native culture to determine if theorfXcluster proteins remain associated with BoNT/A2. To better understand the role of theorfXcluster genes, theorfXcluster proteins ofC. botulinumA2 strains (ORFX1, ORFX3, P47, and the middle a part of NTNH) was expressed using either anEscherichia colior aC. botulinumexpression system in this study. Antibodies against individual expressedorfXcluster proteins were then raised by immunizing a rabbit and mice. These antibodies were then used as probes to investigate the.