Botox - everything we knowabout gene coding for botulinum toxin

Kopčok, Vedrana (2012) Botox - everything we knowabout gene coding for botulinum toxin. Bachelor's thesis, Faculty of Science > Department of Biology.

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Abstract

Clostridium botulinum is anaerobic, Gram-positive, spore-forming rod that produces a potent neurotoxin. The spores are heat-resistant and can survive in foods that are incorrectly or minimally processed. Seven types of botulinum are recognized (A, B, C, D, E, F and G), based on antigenic specificity of the toxin produced by each strain. Types A, B, E and F cause human botulism, types C and D cause botulism in animals. Only few outbrakes of type G have been reported. Most strains produce only one type of toxin, but strains producing dual toxin types have been reported. This neurotoxin complex is composed of the BoNT and several toxin associated proteins known as hemagglutinins (HAs) and the non-toxic non-hemagglutinin protein (NTNH), RNA, and other uncharacterized protein components. The genes encoding the neurotoxin associated protein components of the toxin complex are organized in a cluster called botulinum locus, and their location and composition varies among the different serotypes and strains. Genes are organized in two polycistronic operons (ntnh-bont and ha operons). The gene that separates the two operons encodes BotR/A protein, which is a positive regulator of the expression of the botulinum locus genes. BotR/A is possibly alternative sigma factor. Three different complex species with the discrete sizes 19S (900 kDa), 16S (500 kDa), 12S (300 kDa) may be isolated from C. botulinum type A cultures. To affect their target cells these complexes must dissociate realeasing the free 150 kDa neurotoxin. pH changes, protein concentration and precence of salts influence the dissociation of BoNT/A containing complex. Botulism is a serious, sometimes fatal, disease caused by a botulinum neurotoxin. This toxin, which acts preferentially on peripheral cholinergic nerve endings to block acetylcholine release. Toxin that is ingested or inhaled can bind to epithelial cells and be transported to the general circulation. Toxin that reaches peripheral nerve endings binds to the cell surface then penetrates the plasma membrane by receptor-mediated endocytosis and the endosome membrane by pH-induced translocation. Internalized toxin acts in the cytosol as a metalloendoprotease to cleave polypeptides that are essential for exocytosis.

Item Type: Thesis (Bachelor's thesis)
Supervisor: Ivančić Baće, Ivana
Date: 2012
Number of Pages: 13
Subjects: NATURAL SCIENCES > Biology
Divisions: Faculty of Science > Department of Biology
Depositing User: Silvana Šehić
Date Deposited: 14 Oct 2014 09:07
Last Modified: 14 Oct 2014 09:07
URI: http://digre.pmf.unizg.hr/id/eprint/3029

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