Voltage gating of homotypic Cx47 gap junctions inXenopus oocytes (A, B) and transfected HeLa cells (C, D). A, Graph of initial and steady-state G_j(filled and open triangles, respectively) as a function of V_j. G_j isg_j normalized to its value atV_j = 0. Data represent mean values obtained from five Xenopus oocyte cell pairs with maximum g_j values < 10 μS. Thesolid line is the Boltzmann fit of the steady-state data (see text). B, Representative junctional currents forV_j steps up to ±120 mV in 20 mV increments. Upward and downward currents are elicited by negative and positive V_j values, respectively. Calibration: 500 nA, 2 sec. C, Graph of steady-stateG_j as a function ofV_j in HeLa–Cx47 (filled circles) and HeLa–Cx47-EGFP (open circles) cell pairs. G_j is normalized as described in A. The solid line is a fit of the experimental data to the Boltzmann equation (see text).D, Examples of junctional currents in response to ±30, 50, and 65 mV V_j steps applied to one cell of a HeLa–Cx47 cell pair. Small, repeated positive and negative 20 mV V_j steps were applied to the same cell in between the longer durationV_j steps to regularly monitorI_j. wt, Wild type.