Sci. STKE, 21 December 1999
Channels Shaker Channels do the Twist
Shaker K+ channels from Drosophila are a well-studied example of voltage-gated channels that are essential for neuronal signal transduction. Two groups, Cha et al. and Glauner et al., have now done experiments that move us a step closer to understanding the precise mechanism by which these channels are opened and closed in response to changes in membrane potential. A segment known as S4 is known to contain charged amino acids that participate in sensing voltage changes. These charged residues move across the electric field of the membrane as the channel is opened and closed. By tagging regions of the channel with donors and acceptors, the two groups used fluorescence resonance energy transfer to monitor movement between the subunits of the channel. As residues along the protein sequence near or in the S4 segment were probed, they appeared to alternately move closer or farther apart, suggesting that the S4 region may actually twist in response to voltage changes. Large changes in conformation of the subunits were not detected, and the twisting motion is an appealing model that would help explain how the series of charged residues in the S4 domain can be alternately exposed to the intracellular or extracellular face of the membrane through relatively small movements of regions within the channel subunits.
Cha, A., Snyder, G.E., Selvin, P.R., and Bezanilla, F. (1999) Atomic scale movement of the voltage-sensing region in a potassium channel measured via spectroscopy. Nature 402: 809-813. [Online Journal]
Glauner, K.S., Mannuzzu, L.M., Gandhi, C.S., and Isacoff, E.Y. (1999) Spectroscopic mapping of voltage sensor movement in the Shaker potassium channel. Nature 402: 813-817. [Online Journal]
Citation: Shaker Channels do the Twist. Sci. STKE 1999, tw2 (1999).
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