A Gating Charge Transfer Center in Voltage Sensors

Abstract

Open and Closed Case Voltage-dependent ion channels are gated by voltage sensors that show a switchlike response to voltage differences across the membrane. Tao et al. (p. 67 ; see the cover) used mutagenesis, electrophysiology, and x-ray crystallography to gain insight into the molecular basis of this response in voltage-dependent potassium channels. An occluded site was identified that catalyzes translation of positive charges across the membrane. The closed channel appears to be associated with a distribution of conformations, depending on the degree of hyperpolarization of the membrane, whereas the open channel appears to be associated with a specific conformation. Thus, the transition of the ion channel from open to closed occurs over a very small voltage difference.