Edema factor

The anthrax toxin is a tripartite toxin and consists ofthe binding component protective antigen (PA), the lethal factor (LF), which is a metalloprotease, and the edema factor (EF), which is a calmodulin-dependent adenylyl-cyclase. Both enzyme components are translocated via PA into target cells. PA is activated by furin-induced cleavage and forms heptamers, which are similar to the binding components of C2 toxin and iota toxin. In the low pH compartment of endosomes, the heptamers form pores to allow translocation of LF and EF. LF cleaves six of the seven MEKs (MAPK-kinases) thereby inhibiting these enzymes. The functional consequence is the blockade of the MAPK pathways that control cell proliferation, differentiation, inflammation, stress response, and survival. Whether this is the reason for the LT-induced cell death of macrophages is not clear [1]. 

Variations in the manufacturing process of 2,4,5-trichloro- and pentachlorophenol (but not 2,4-dichlorophenol) have sometimes resulted in contamination of the product by small amounts of heterocyclic impurities (4,5). Of these, the chlorinated dibenzo-p-dioxins such as TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) have received much scientific and public attention because of their real or potential toxicity 6, 7), [Chick edema factor, a curious toxicological problem to poultry producers for several years, has been shown to be composed of chlorodibenzo-p-dioxins (8).]... 

A consistent pericardial edema in chickens gave rise to the term chick edema disease (chick edema factor) (I). Two known outbreaks of the disease in the broiler industry resulted in a great loss of chickens. A lipid residue from the manufacturing fatty acids, being used as a feed ingredient, was a principal source of the toxic substance. Contamination of the lipid component with polychlorodibenzo-p-dioxins was attributed as the causal agent. 

In addition to its extremely high oral toxicity, skin contact with substances containing 2,3,7,8-tetrachlorodibenzo-p-dioxin may allow toxicity in the form of chloracne, a condition characterized by eruptions of the skin on the face, neck, and back. Also, chlorinated dibenzo-p-dioxins have been associated with the chick edema factor, a disease of chicks associated with contaminated fats or oils used in the manufacture of their feed. 

The anthrax bioterrorist attacks that followed the events of September 11th 2001 resulted in a renewed interest BadUus anthracis, the causative agent of this disease. Research has focused on the development of better vaccines than the one currently available. It has been estimated that the aerosolized release of 100 kg of anthrax spores upwind of Washington DC would cause mortalities of 130,000-3,000,000 [63]. Nonetheless, wild-type Bacillus anthracis is susceptible to conventional antibiotics, including penicillin, oxyfloxacin and ciprofloxacin. The problem lies not with the bacterial infection itself, but with three proteins released by the bacteria - protective antigen (PA, 83 kDa), lethal factor (LF, 90 kDa) and edema factor (EF, 89 kDa) -known as anthrax toxins [63]. 

Anthrax Anthrax is a toxin with three separate components a protective antigen (PA), an edema factor (EF), and a lethal factor (LF). 

Very recently the protein structures of ACE with the bound inhibitors Lisinopril (Fig. 4) and Captopril were published (101,102). Also the protein structure of the LF from Bacillus anthracis (PDB-Code 1J7N) caused a sensation, which is now available to the public (Fig. 14b) (103). LF is part of the toxic exotoxin complex composed of three distinct proteins (protective antigen PA, the lethal factor LF and the edema factor EF), and is thought to be the most toxic... 

Anthrax toxin is a bacterial toxin from Bacillus anthracis consisting of three parts protective antigen (PA), lethal factor (LF) and edema factor (EF). Both LF and EF compete for binding sites on the PA protein. The PA protein binds with high affinity to an as yet unknown receptor on macrophages and related cell types. When PA is internalized by the target cells, it functions as a shuttle protein for either EF or LF. Intracellularly, in the acidic environment of the endosome, EF and LF are capable of entering the cytosol by pH-dependent pore formation [139]. 

Chick edema disease became a serious economic problem by the mid-1950s, by which time millions of broilers had succumbed to it in the U.S. The problem was traced to toxic components in the unsaponifiable fraction of certain low cost feed fats Introduced into the chick diet to increase the caloric intake (ref. 121c). Symptoms included fluid in the heart sack and abdominal cavity, subcutaneous edema and liver necrosis. Injection of purified chick edema factor into fertile eggs resulted in lower hatch yield, embryonic deformities and edema. Unhatched embryos exhibited a variety of defects (malformed beaks, leg deformities, no development of the right mesencephalon, and eye defects). Hatched embryos were growth-retarded, with sparse and defective feathers. The isolated toxin was ultimately identified as 1.2,3,7.8,9-... 

Campbell AD, Firestone D, Westly B. 1971. Chick edema factor—toxic dioxins. In WestleyB, ed. International Symposium on identification and measurement of environmental pollutants, Ottawa, Ontario, Canada, June 14-17, 1971. Ottawa, Canada The Symposium, 105-108. 

Edema factor of anthrax is one of the three exotoxins produced by the bacteria. The primary sequence is only slightly homologous to other adenylyl cyclases. When it enters the host cells, edema factor acts as an adenylyl cyclase and transforms ATP to cAMP efficiently. The structme of CaM-edema factor of anthrax complex has been obtained (Figure 9). In the CaM-edema factor complex, only the C-terminal lobe binds two calcium ions while the N-terminal lobe is empty. CaM remains extended and is deeply inserted between the catalytic and the a-helical domains of this exotoxin with a large number of residues of CaM iuvolved in the interaction. CaM binding results in a large domain reorientation of edema factor. The helical domain of edema factor undergoes a 15 A translation and a 30° rotation. The CaM inserted site is far from the catalytic site and the... 

Figure 9 The structures of (a) calmodulin-free (1K8T) (b) calmodulin-bound (1K93) forms of Edema factor ...

Lacy, D.B., Mourez, M., Fouassier, A., Collier, R.J. (2002). Mapping the anthrax protective antigen hinding site on the lethal and edema factors. J. Biol. Chem. 277 3006-10. 

Shen, Y., Zhukovskaya, N.L., Guo, Q., Florian, J., Tang, W-J. (2005). Calcium-independent calmodulin binding and two-metal-ion catalytic mechanism of anthrax edema factor. Eur. Mol. Biol. Org. J. 24 929 1. 

All fat products must be below tolerances for toxic chemicals and pesticide residues certification is available from most renderers fats used in poultry rations must be free of the chick edema factor and all fats should be devoid of contaminants such as heavy metals. 

Consistent performance in today s feed conversion-animal production industries requires consistent feedstuffs. In addition to providing products free of chick edema factors, pesticides, herbicides, polychlorinated biphenyls (PCBs), and other hazardous contaminants, the tallow and grease supplier is expected to deliver products with increasingly consistent fatty acid profiles. This requires appropriate... 

Endocytosis may not be required for the entry of an invasive adenylate cyclase from Bordello pertussis (Hanski and Ferfel, 1985 Donovan and Storm, 1990). This is a single chain protein (mol. wt. approx. 200 kDa) which resembles the edema factor from anthrax toxin in that it must interact with calmodulin to become active. In contrast to anthrax toxin, it consists of only one polypeptide which is, however, easily cleaved by proteases and thereby activated. An enzymatically active 45 kDa fragment is not active on whole cells, but it could in conjunction with the rest of the molecule enter the cytosol. The facts that this toxin acts much more rapidly than anthrax toxin, and that it is active even at 4 °C and on erythrocytes that have little, if any, endocytosis, suggest that the toxin is able to penetrate directly through the cell surface membrane. 

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