FIG. 5.

Control of the inward current by cytosolic K⁺. Plasma membrane conductance at −140 mV plotted as a function of extracellular K⁺ activity. Pipette solutions were LKM and HKM for 10 (■) and 129 (•) mM cytosolic K⁺, respectively. Conductance was calculated as I_ss/(−140 − E_K), where I_ss is the steady-state current and E_K is the equilibrium potential for K⁺. Data are fitted with Michaelis-Menten functions. For 10 mM cytosolic K⁺, K_m was 90 ± 50 mM and V_max was 1.25 ± 0.31 nS; for 129 mM cytosolic K⁺, K_m was 62 ± 55 mM and V_max was 0.44 ± 0.10 nS. Data for 10 mM cytosolic K⁺ were taken from Fig. 2C.