Anthrax toxin is composed of three proteins: protective antigen (PA), lethal factor (LF), and edema factor (EF). These proteins individually cause no known physiological effects in animals but in pairs produce two toxic actions. Injection of PA with LF causes death of rats in 60 min, whereas PA with EF causes edema in the skin of rabbits and guinea pigs. The mechanisms of action of these proteins have not been determined. It is shown here that EF is an adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] produced by Bacillus anthracis in an inactive form. Activation occurs upon contact with a heat-stable eukaryotic cell material. The specific activity of the resulting adenylate cyclase nearly equals that of the most active known cyclase. In Chinese hamster ovary cells exposed to PA and EF, cAMP concentrations increase without a lag to values about 200-fold above normal, remain high in the continued presence of toxin, and decrease rapidly after its removal. The increase in cAMP is completely blocked by excess LF. It is suggested that PA interacts with cells to form a receptor system by which EF and perhaps LF gain access to the cytoplasm.

https://www.pnas.org/content/pnas/79/10/3162.full.pdf

Anthrax toxin edema factor: a bacterial adenylate cyclase that increases cyclic AMP concentrations of eukaryotic cells.

Extracellular vesicles (EVs) are produced by all domains of life In Gram-negative bacteria, EVs are produced by the pinching off of the outer membrane; however, how EVs escape the thick cell walls of Gram-positive bacteria, mycobacteria and fungi is still unknown Nonetheless, EVs have been described in a variety of cell-walled organisms, including Staphylococcus aureus, Mycobacterium tuberculosis and Cryptococcus neoformans These EVs contain varied cargo, including nucleic acids, toxins, lipoproteins and enzymes, and have important roles in microbial physiology and pathogenesis In this Review, we describe the current status of vesiculogenesis research in thick-walled microorganisms and discuss the cargo and functions associated with EVs in these species

/pdf/through-the-wall-extracellular-vesicles-in-gram-positive-3gejw9pnxh.pdf

Through the wall: extracellular vesicles in Gram-positive bacteria, mycobacteria and fungi

Immunity to intracellular bacteria.

The bacterium Bacillus anthracis causes the death of macrophages, which may allow it to avoid detection by the innate immune system. We found that B. anthracis lethal factor (LF) selectively induces apoptosis of activated macrophages by cleaving the amino-terminal extension of mitogen-activated protein kinase (MAPK) kinases (MKKs) that activate p38 MAPKs. Because macrophages that are deficient in transcription factor nuclear factor κB (NF-κB) are also sensitive to activation-induced death and p38 is required for expression of certain NF-κB target genes, p38 is probably essential for synergistic induction of those NF-κB target genes that prevent apoptosis of activated macrophages. This dismantling of the p38 MAPK module represents a strategy used by B. anthracis to paralyze host innate immunity.

/pdf/macrophage-apoptosis-by-anthrax-lethal-factor-through-p38-1478a28n68.pdf

Macrophage Apoptosis by Anthrax Lethal Factor Through p38 MAP Kinase Inhibition

Proteolytic cleavage of the protective antigen (PA) protein of anthrax toxin at residues 164-167 is necessary for toxic activity. Cleavage by a cellular protease at this sequence, Arg-Lys-Lys-Arg, normally follows binding of PA to a cell surface receptor. We attempted to identify this protease by determining its sequence specificity and catalytic properties. Semi-random cassette mutagenesis was used to generate mutants with replacements of residues 164-167 by Arg, Lys, Ser, or Asn. Analysis of 19 mutant proteins suggested that lethal factor-dependent toxicity required the sequence Arg-Xaa-Xaa-Arg. Based on these data, three additional mutants were constructed with the sequences Ala-Lys-Lys-Arg, Arg-Lys-Lys-Ala, and Arg-Ala-Ala-Arg. Of these mutant proteins, Arg-Ala-Ala-Arg was toxic, confirming that the cellular protease can recognize the sequence Arg-Xaa-Xaa-Arg. The mutant containing the sequence Ala-Lys-Lys-Arg was also toxic but required > 13 times more protein to produce equivalent toxicity. This sequence specificity is similar to that of the ubiquitous subtilisin-like protease furin, which is involved in processing of precursors of certain receptors and growth factors. Therefore we tested whether a recombinant soluble furin would cleave PA. This furin derivative efficiently cleaved native PA and the Arg-Ala-Ala-Arg mutant but not the nontoxic PA mutants. In addition, previously identified inhibitors of furin blocked cleavage of receptor-bound PA. These data imply that furin is the cellular protease that activates PA, and that nearly all cell types contain at least a small amount of furin exposed on their cell surface.

https://www.pnas.org/content/pnas/89/21/10277.full.pdf

Anthrax toxin protective antigen is activated by a cell surface protease with the sequence specificity and catalytic properties of furin

Fœtal Erythritol: A Cause of the Localization of Brucella Abortus in Bovine Contagious Abortion

J. Keppie

Papers

Fœtal Erythritol: A Cause of the Localization of Brucella Abortus in Bovine Contagious Abortion

The Chemical Basis of the Virulence of Bacillus anthracis. V. The Specific Toxin produced by B. anthracis in vivo.

The chemical basis of the virulence of bacillus anthracis. ix. its aggressins and their mode of action.

The role of erythritol in the tissue localization of the brucellae.

The chemical basis of the virulence of Bacillus anthracis. III. The role of the terminal bacteraemia in death of guinea-pigs from anthrax.