Fast and slow kinetics of porin channels from Escherichia coli reconstituted into giant liposomes and studied by patch-clamp.
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 -100 mV. 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 cooperation 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.
Berrier
C
C
Laboratoire des Biomembranes, URA CNRS 1116, Université Paris-Sud, Orsay, France.
Coulombe
A
A
Houssin
C
C
Ghazi
A
A
D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D007700:Kinetics; D008081:Liposomes / Q000378:metabolism*; D008564:Membrane Potentials
D001425:Bacterial Outer Membrane Proteins; D008081:Liposomes