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

AbstractE. 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