Gating Mechanisms of Shaker Potassium Channels
Voltage-gated ion channels are a class of proteins that change conformation in response to changes in the electrical potential across a cell membrane. By opening and closing in response to changes in membrane potential, they regulate the movement of ions across the cell membrane. The ability of these proteins to change conformation rapidly from closed to open states in response to membrane voltage changes of only a few millivolts suggests a highly sophisticated molecular machinery for sensing membrane voltage and changing conformation. The nature of the gating mechanisms of these molecules has been the object of intensive study by membrane biophysicists over the last forty years (see Hille 1984). From these studies a number of insights about the molecular operation of these channels have emerged. Voltage-dependent gating comes about by a difference in the distribution of charged entities of the channel protein between different conformations. The larger the charge movement parallel to the electrical field across the membrane, between states, the greater the voltage dependence of the transition rate between the states. Many voltage-gated channels inactivate after opening during a step change in voltage by a conformational change that is not very voltage dependent and therefore does not involve a significant movement of charge through the membrane.
KeywordsLysine Polypeptide Arginine Glutamine Trypsin
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