FIGURE 2.
KcsA/MloK1 possesses proton-activated KcsA-like single-channel current activity and is modulated by cAMP at the single-molecule level. A, single-channel recordings from KcsA/MloK1 WT; B, KcsA/MloK1 E71A (which is noninactivating). Single-channel recordings from a representative lipid bilayer containing KcsA/MloK1 E71A perfused from pH 4 (top trace, two channels open at the same time) to pH 5.25 (middle trace) and finally to pH 5.25 and 1 μm cAMP (bottom trace). Traces were obtained in 100 mm symmetrical K+ at 100 mV and filtered at 200 Hz for display. The dashed line corresponds to the closed state. At pH 4 (top trace), two channels are open concomitantly with a Po of ∼1. C, single-channel current-voltage plots from the experiments shown partially in A and B for KcsA/MloK1 WT (black circles) and KcsA/MloK1 E71A (open circles) channels.