The non-haemolytic enterotoxin (Nhe) is one of two three-component enterotoxins responsible for the diarrhoeal food-poisoning syndrome caused by . Nhe is composed of NheA, NheB and NheC. The three genes encoding the Nhe components constitute an operon, and the transcriptional start site is located 61 bp upstream of the translational start site. The genes were cloned separately, and expressed in either or . Separate expression showed that all three components were required for biological activity. In addition, NheA and NheB were purified from culture supernatants. As NheC seems to be expressed in only small amounts by , NheC was expressed and purified as a histidine-tagged fusion protein. The maximum cytotoxic activity was obtained when the molar ratio between NheA : NheB : His-NheC was 10 : 10 : 1, and it was shown that NheB was the binding component of the enterotoxin complex.


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