title: Comparing the temperature-dependent conductance of the two structurally similar E. coli porins OmpC and OmpF.
abstract: The temperature-dependent ion conductance of OmpC, a major outer membrane channel of Escherichia coli, is predicted using all-atom molecular dynamics simulations and experimentally verified. To generalize previous results, OmpC is compared to its structural homolog OmpF at different KCl concentrations, pH values, and a broad temperature range. At low salt concentrations and up to room temperature, the molecular modeling predicts the experimental conductance accurately. At high salt concentrations above 1 M KCl and above room temperature, the simulations underestimate the conductance. Moreover, the temperature dependence of the channel conductance is different from that of the bulk, both in experiment and simulation, indicating a strong contribution of surface effects to the ion conductance. With respect to OmpC, subconductance levels can be observed in experiments only. Subconductance and gating levels can be clearly distinguished by their differences in conductance values and temperature-dependent behavior. With increasing temperature, the probability of a subconductance state to occur, increases, while the dwell time is decreased. The open probability, frequency, and dwell time of such states is largely pH- and KCl concentration-independent, while their amplitudes show a lower increase with increasing salt concentration than gating amplitudes. Voltage dependence of subconductance has been found to be negligible within the uncertainty of the measurements.
authors.affiliation: School of Engineering and Science, Jacobs University Bremen, Bremen, Germany.
authors.forename: István
authors.initials: I
authors.lastname: Biró
authors.forename: Soroosh
authors.initials: S
authors.lastname: Pezeshki
authors.forename: Helge
authors.initials: H
authors.lastname: Weingart
authors.forename: Mathias
authors.initials: M
authors.lastname: Winterhalter
authors.forename: Ulrich
authors.initials: U
authors.lastname: Kleinekathöfer
mesh_terms: D003198:Computer Simulation; D004553:Electric Conductivity; D004926:Escherichia coli; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D056004:Molecular Dynamics Simulation; D018272:Porins / Q000737:chemistry* / Q000378:metabolism*; D016062:Porosity; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D013696:Temperature; D013816:Thermodynamics
chemical_list: D029968:Escherichia coli Proteins; C113724:OmpC protein; C109237:OmpF protein; D018272:Porins