The Clostridium perfringens Enterotoxin (CPE)


CPE is the cause of around 20% of all food poisoning; this equates to approximately 1 million cases per year in mainland UK. CPE is produced in large amounts by sporulating C.perfringens, and can make up over 15% of the total protein mass of a sporulating cell. Similar to all Enterotoxins, CPE causes diarrhoea by altering membrane permeability in the small intestines of mammals.

However, its method of action is poorly understood, and currently, there are 2 school of thought as to how CPE accomplishes this:

1.CPE forms pores in epithelial membrane plasma membranes

2.CPE removes host tight junction proteins (certain Claudins and Occludin), allowing interstitial fluid to seep into the gut

Pore forming

It is thought that CPE binds certain host membrane protein and uses them as anchors to raise the local concentration of CPE until it is sufficient to causes oligomerisation/membrane insertion. It has been shown that small complexes (CPE containing complexes isolated weighing ~90Kda) can be formed at 4oC but larges complexes (CPE containing complexes weighing 210Kda ) only form at 37oC. It is assumed that these large complexes require a certain degree of membrane fluidity to form and are post-insertion complexes i.e. the active pore form. Upon formation of this pore, ions, amino acids, nucleotides (anything small than 3Kda) may flow out of the cell, and water rushes in. This influx of water bursts the cell i.e CPE has cytolethal activity.

Tight junction degradation

CPE has shown to both bind to tight junctions (via immuno-fluorescence studies) and degrade the characteristic protein belt observed in electron microscopy of these structures.

Progress

Several crystal forms have been obtained and initial diffraction has been characterised. We are currently screening for heavy atom derivatives.
Selection of CPE crystals

The Project is in collaboration with Prof Bruce McClane at the University of Pittsburgh school of Medcine.

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