Import and export of bacterial protein toxins (original) (raw)
Related papers
Production of an E. coli toxin protein; Colicin A in E. coli using an inducible system
Turkish Journal of Chemistry, 2003
Colicins are bacterial toxins that kill Escherichia coli and related cells; their mode of action is of interest in protein import and toxicology. Colicins translocate across the E. coli outer membrane and periplasm by interacting with several receptors. This translocation process involves interaction of the colicin with the outer membrane porin OmpF and subsequently with the integral membrane protein TolA. The N-terminal domain of colicin N is involved in the import process. Our aim was to produce a large quantity of colicin A for functional and structural studies. It is a prerequisite to have a correctly folded and stable protein for these studies. The commonly utilised expression system uses the Lex A promoter, which requires induction with toxic mitomycin C, though the yield is low. Here we present the production of an E. coli toxin and its immunity protein in E. coli using a safe inducible promoter.
Bacterial protein toxins penetrate cells via a four-step mechanism
FEBS Letters, 1994
Bacteria produce several protein toxins that act inside cells. These toxins bind with high affinity to glycolipid or glycoprotein receptors present on the cell surface. Binding is followed by endocytosis and intracellular trafficking inside vesicles. Different toxins enter different intracellular routes, but have the common remarkable property of being able to translocate their catalytic subunit across a membrane into the cytosol. Here, a toxin modifies a specific target with ensuing cell alterations, necessary for the survival and diffusion strategies of the toxin producing bacterium.
Protein toxins from plants and bacteria: Probes for intracellular transport and tools in medicine
FEBS Letters, 2010
A number of protein toxins produced by bacteria and plants enter eukaryotic cells and inhibit protein synthesis enzymatically. These toxins include the plant toxin ricin and the bacterial toxin Shiga toxin, which we will focus on in this article. Although a threat to human health, toxins are valuable tools to discover and characterize cellular processes such as endocytosis and intracellular transport. Bacterial infections associated with toxin production are a problem worldwide. Increased knowledge about toxins is important to prevent and treat these diseases in an optimal way. Interestingly, toxins can be used for diagnosis and treatment of cancer.
General aspects and recent advances on bacterial protein toxins
Bacterial pathogens produce protein toxins to influence host-pathogen interactions and tip the outcome of these encounters toward the benefit of the pathogen. Protein toxins modify host-specific targets through posttranslational modifications (PTMs) or noncovalent interactions that may inhibit or activate host cell physiology to benefit the pathogen. Recent advances have identified new PTMs and host targets for toxin action. Understanding the mechanisms of toxin action provides a basis to develop vaccines and therapies to combat bacterial pathogens and to develop new strategies to use toxin derivatives for the treatment of human disease.
Molecular Microbiology, 2014
28 MARTX (multifunctional autoprocessing repeats-in-toxin) family toxins are produced by 29 V.cholerae, V.vulnificus, A.hydrophila and other Gram-negative bacteria. Effector domains of 30 MARTX toxins cross the cytoplasmic membrane of a host cell through a putative pore formed 31 by the toxin's glycine-rich repeats. The structure of the pore is unknown and the translocation 32 mechanism of the effector domains is poorly understood. We examined the thermodynamic 33 stability of the effector domains of V.cholerae and A.hydrophila MARTX toxins to elucidate the 34 mechanism of their translocation. We found that all but one domain in each toxin are 35 thermodynamically unstable and several acquire a molten globule state near human 36 physiological temperatures. Fusion of the most stable cysteine protease domain to the 37 adjacent effector domain reduces its thermodynamic stability ~1.4 fold (from ΔG H 2 O 21.8 to 38 16.1 kJ/mol). Precipitation of several individual domains due to thermal denaturation is 39 reduced upon their fusion into multi-domain constructs. We speculate that low thermostability 40 of the MARTX effector domains correlates with that of many other membrane-penetrating 41 toxins and implies their unfolding for cell entry. This study extends the list of thermolabile 42 bacterial toxins, suggesting that this quality is essential and could be susceptible for selective 43 targeting of pathogenic toxins.
Trojan horse or proton force: Finding the right partner(s) for toxin translocation
Neurotoxicity Research, 2006
Much is known about the structure function relationships of a large number of bacterial protein toxins, the nature of their cell surface receptors, and their enzymatic activities which lead to the inactivation of their respective cytosolic targets. Despite this wealth of knowledge a detailed understanding of the mechanisms which underlie translocation of the catalytic domain across the eukaryotic cell membrane to the cytosol, the penultimate event in the intoxication process, have been slow in developing. In the case of diphtheria toxin, two prominent hypotheses have been advanced to explain how the catalytic domain is translocated from the lumen of endocytic vesicles to the target cell cytosol. We discuss each of these hypotheses and provide an overview of recent observations that tend to favor a mechanism employing a Cytosolic Translocation Factor complex in the entry process. This facilitated mechanism of translocation appears to rely upon protein-protein interactions between conserved domains within the transmembrane domain of diphtheria toxin and host cell factors to effect delivery of the enzymatic moiety. We have recently identified a 10 amino acid motif in the transmembrane domain of diphtheria toxin that is conserved in anthrax Lethal and Edema Factors, as well as in botulinum neurotoxins A, C and D. Stable eukaryotic cell transfectants that express a peptide containing this motif become resistant to the toxin, and sensitivity is completely restored by co-expression of siRNA which inhibits peptide expression. Data obtained from use of the protein fusion toxin DAB389IL-2 in cytotoxicity assays using susceptible Hut 102/6TG and resistant transfectant Hut102/6TG-T1 cells, as well as pull down assays have led to the formulation of a working model of facilitated delivery of the diphtheria toxin catalytic domain to the cytosol of target cells which is discussed in detail.
Bacterial toxins and their application
Molecular Biology, 2000
The review deals with the structure of protein bacterial toxins, steps of the toxin molecule interaction with the target cell, molecular mechanisms of the toxic effect, as well as with the fields of application of toxins as research tools and as medicinal preparations.
Molecular mechanisms of action of bacterial protein toxins
Molecular Aspects of Medicine, 1994
Clostridium is a genus of sporulating and anaerobic Gram-positive, rod-shaped bacteria that includes more than 150 species. These bacteria are widely distributed in the environment and in anaerobic regions of the intestines of several animals, where they are typically found as spores, which are resistant to physical and chemical stresses and can persist for long periods of time until favourable conditions enable germination 1,2 . Under appropriate environmental conditions (such as humidity, nutrients and the absence of oxygen), spores germinate into vegetative cells; conversely, exposure to oxygen, as well as water and nutrient deprivation, trigger sporulation. Several clostridia, including Clostridium difficile, Clostridium perfringens and Clostridium sordelli, are pathogenic, owing to the release of protein toxins, but only a few species are neurotoxigenic. For example, Clostridium tetani produces tetanus neurotoxin, which blocks neurotransmitter release in spinal cord interneurons and causes the spastic paralysis of tetanus 3 . In addition, six phylogenetically distinct clostridia produce more than 40 different botulinum neurotoxins (BoNTs) (BOX 1). BoNTs consist of three primary domains: two of these domains enable binding to nerve terminals and translocation of the toxin into the neuronal cytosol, and the third domain comprises a metalloprotease that inhibits the release of neurotransmitter by peripheral nerve terminals (BOX 2), which causes the flaccid paralysis and autonomic dysfunctions that are typical of botulism 2,4 . The neurospecificity and toxic potency of BoNTs make them the most powerful known toxins, and they are potential bioterrorism weapons 5,6 . By contrast, their absolute neurospecificity has enabled BoNTs to be used as effective therapeutic agents for human diseases that Neurotransmitter An endogenous chemical that transmits signals across a synapse from a neuron to a postsynaptic cell.