Effects of pH on bacterial porin function.
Porin is a trimeric channel-forming protein in the outer membrane of Gram-negative bacteria. Functions of the porins OmpF, OmpC, and PhoE from Escherichia coli K12 were analyzed at various pHs. Preliminary results from bilayer lipid membrane and liposome swelling assays indicated that in vitro porin has at least two open-channel configurations with a small and a large size. The small channels were stabilized at low pH while the larger channels were detected under basic conditions. The size switch occurred over a very narrow range near neutral pH, and the two major open-channel configurations responded differently to variations in voltage. The presence of two or more pH-dependent substates of porin could explain the variability in pore diameter measured by others and suggests a more dynamic role for porin in the cell.
Todt
J C
JC
Department of Biochemistry, Michigan State University, East Lansing 48824.
Rocque
W J
WJ
McGroarty
E J
EJ
D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism* / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D015640:Ion Channel Gating; D007473:Ion Channels / Q000502:physiology*; D008051:Lipid Bilayers; D008081:Liposomes; D008564:Membrane Potentials
D001425:Bacterial Outer Membrane Proteins; D007473:Ion Channels; D008051:Lipid Bilayers; D008081:Liposomes