Fluctuation-Driven Molecular Transport Through an Asymmetric Membrane Channel

URL:http://link.aps.org/doi/10.1103/PhysRevLett.93.238102 DOI:10.1103/PhysRevLett.93.238102Channel proteins that selectively conduct molecules across cell membranes often exhibit an asymmetric structure. By means of a stochastic model, we argue that channel asymmetry in the presence of nonequilibrium fluctuations, fueled by the cell's metabolism as observed recently, can dramatically influence the transport through such channels by a ratchetlike mechanism. For an aquaglyceroporin that conducts water and glycerol, we show that a previously determined asymmetric glycerol potential leads to enhanced inward transport of glycerol, but for unfavorably high glycerol concentrations also to enhanced outward transport that protects a cell against poisoning.We acknowledge financial support from the University of Missouri Research Board, the Institute for Theoretical Sciences, and the Department of Energy (DOE Contract No. W-7405-ENG-36) for I. K., and the National Institutes of Health (NIH 1-R01-GM067887-01) for K. S