Single channel behavior of matrix porin of Escherichia coli.
Porins are trimeric proteins in the outer membranes of Gram-negative bacteria. Several of them, among them matrix porin of Escherichia coli, form symmetrically voltage-gated ion channels in planar bilayers. Trimers exhibit negative resistance at potentials larger than +/- 90mV. Here we show that, after two pores within a trimer close irreversibly, the remaining third pore shows channel properties distinct from those observed in the trimer. This residual pore exhibits an asymmetric current-voltage dependence with a pronounced polarity-dependent shift toward low potentials and rates of channel-closing and opening that are one to two orders of magnitude faster than those observed for single channels in a reversibly voltage-dependent trimer. Rectification of single channels thus resembles that of a voltage-gated channel type observed in outer membrane patches of E.coli spheroblasts, hinting at the relevance of the phenomenon in vivo.
Buehler
L K
LK
University of Basel, Dept. of Microbiology, Switzerland.
Rosenbusch
J P
JP
D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D004553:Electric Conductivity; D004926:Escherichia coli; D015640:Ion Channel Gating / Q000502:physiology; D007473:Ion Channels / Q000502:physiology*; D008051:Lipid Bilayers / Q000378:metabolism; D046911:Macromolecular Substances; D018272:Porins; D011189:Potassium Chloride; D012965:Sodium Chloride
D001425:Bacterial Outer Membrane Proteins; D007473:Ion Channels; D008051:Lipid Bilayers; D046911:Macromolecular Substances; D018272:Porins; D012965:Sodium Chloride; D011189:Potassium Chloride