Fluctuation-driven molecular transport through an asymmetric membrane channel.
Channel 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.
Kosztin
Ioan
I
Department of Physics & Astronomy, University of Missouri, Columbia, MO 65211, USA.
Schulten
Klaus
K
D020346:Aquaporins / Q000502:physiology; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000502:physiology; D005990:Glycerol / Q000737:chemistry; D007473:Ion Channels / Q000737:chemistry*; D008958:Models, Molecular; D015233:Models, Statistical; D009068:Movement; D016012:Poisson Distribution; D011506:Proteins / Q000737:chemistry*; D013269:Stochastic Processes; D014867:Water / Q000737:chemistry
D020346:Aquaporins; D029968:Escherichia coli Proteins; D007473:Ion Channels; D011506:Proteins; D014867:Water; C078043:GlpF protein, E coli; D005990:Glycerol