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Escherichi coli glycerol uptake facilitator (GlpF)

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Atomic force microscopy measurements of the surfaces of cells lead to a bizarre discovery: single cells twitch with their surfaces. When the microscope feeds a microphone one hears the murmur, shrieking, or singing of cells. But why do cells sing? A recent report (covered in a news report) suggests that the twitching motion of cell membranes can help cells directionally transport nutriments across their cell wall. Earlier results of computer simulations that described the energetics of glycerol (a nutriment for E. coli) conduction across an aquaglyceroporin membrane channel (see June 2002 highlight) combined with a mathematical analysis of channel transport concludes that the twitching motion of cells leads the channel to act as a ratchet: the twitching moves the glycerol, the channel energetics discourages backslip such that the glycerol moves in one direction. The direction is outside - in when glycerol is in short supply, and inside - out when there is too much of it. The finding has deep implications for other biological channels showing how they can use energy from pulsating membranes to drive solutes through.