A40V and G45E mutants make functional cell–cell channels. (A) Bar graph showing junctional conductances, g_j (mean ± SEM), measured in oocyte pairs injected with H₂O (control, n = 10), WT Cx26 (n = 12), A40V (n = 8), and G45E (n = 7). Coupling was robust for WT Cx26 and both mutants compared with the control. Representative examples of junctional currents (left) along with steady-state G_j-V_j relationships (right) obtained from WT Cx26 (n = 4), A40V (n = 3), and G45E (n = 4) cell pairs. G_j is g_j normalized to the maximum about V_j = 0. Records were taken from oocytes that were paired for shorter times to avoid series access resistance errors that accompany strong coupling. V_j steps between ±120 mV were applied in 10-mV increments. (B) Bar graph showing junctional conductances (mean ± SEM) measured in N2A cell pairs transfected with A40V and G45E (n = 42 for A40V, and n = 53 for G45E). Examples of junctional currents are shown below. V_j steps between ±120 mV were applied in 10-mV increments.