Fast and slow kinetics of porin channels from Escherichia coli reconstituted into giant liposomes and studied by patch‐clamp

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Abstract
E. coli porins (OmpF and OmpC) were purified and reconstituted into liposomes which were enlarged to giant proteoliposomes by dehydration—rehydration and studied by patch‐clamp. The porins could be closed by voltage pulses under −100mV. The kinetics of closure was slow, with closure events of about 200 pS in 0.1 M KCl. Rapid fluctuations (in the millisecond range) of about one third (60–70 pS) of the large closure steps were also observed. The data are interpreted as follows: an increase in membrane potential favours the cooperative transition of multimers towards an inactivated state, while monomers which have not been inactivated can flicker rapidly between an open and a short‐lived closed state.