Topology of the amphipathic helices of the colicin A pore-forming domain in E. coli lipid membranes studied by pulse EPR.

Colicin A is a water-soluble pore-forming protein that kills cells, which are not protected by an immunity protein, by inserting specific helical segments of the toxin subdomain into the cytoplasmic membrane to form voltage-dependent ion channels. This leads to depolarization of the cell membrane followed by depletion of the intracellular ATP levels and finally to cell death. The formation of the integral membrane voltage-gated ion channel is known to be accompanied by a conformational transition.