In Vivo Measurements Of a Ca2+- And Voltage-Activated K+ Channel Intramolecular Distances Using Genetically Encoded Reporters

Abstract

In contrast, at such negative voltages, Hþ at pH ¼ 6.2 was much less effective in increasing open probability, leading to the estimated C value ¼ ~1.3, placing Hþ between Ca2þ and Mg2þ in the ability to promote opening in the absence of voltage sensor activation. Likewise, at the respective saturation concentrations, Hþ was less effective than Ca2þ at regulating channel kinetics. Our electrophysiological measurements and simulations collectively suggest that Hþ is a partial agonist of the RCK1 high-affinity Ca2þ sensor and that a small change in the relative position of His and Asp residues in the sensor, ~0.1 nm, may underlie the activation of the channel by Hþ. Supported by NIH.