Figure 12.

Junctional current (Ij) and single channel conductance (γj) monitored by a double, whole-cell clamp in HeLa cells stably transfected with Cx43, during uncoupling by 100% CO₂. At Vj = 55 mV, the fast Vj-gating of the last five open channels (left side) is manifested by quick (~2 ms) Ij flickering between open (γj main state; top yellow line), and residual (γj residual; pink dashed-line), states, with a γj (residual)/γj (main state) ratio of 20%–25%. In contrast, the chemical/slow gate closes the channel completely (bottom yellow line) by a slow Ij transition (~10 ms; insets a and c). Each channel reopens by a slow transition (~10 ms) from closed to open state (right side and insets b and d). Sampling points (green dots in a and b, and circles in c and d) were recorded at 1 ms intervals. The slow transitions often display fluctuations during channel closing (inset c) or opening (inset d), suggesting that a large particle, like a CaM lobe, flickers in and out of the channel’s mouth (or competes with other CaM lobes) before settling in its final position. Adapted from Reference [161].