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Fig. 7. Voltage-gating properties of homotypic 3, and heteromeric 8-G22R and 3 channels. (A) The decay in junctional current (I_j) induced by transjunctional voltage (V_j) was plotted as a function of time for channels comprised of 3 (left), and 8-G22R plus 3 (right). V_j was stepped in 20-mV increments to ±120 mV. At all potentials >±20 mV, heteromeric 8-G22R and 3 channels showed a more rapid current decay of greater magnitude. (B) Analysis of channel kinetics. Representative initial current decays for gap junctions comprised of homotypic 3 connexin (left), and heteromeric 8-G22R with 3 connexins (right) after application of +80 mV transjunctional voltage. Current traces were fit to a mono-exponential decay to determine the time constant, . Heteromeric 8-G22R and 3 channels closed significantly faster than homotypic 3 channels (P<0.05). values are the mean ± s.e. of four independent experiments. (C) Comparison of equilibrium conductance. Steady-state conductance was measured when current decay reached equilibrium, normalized to the values at ±20 mV and plotted as a function of V_j. The steady-state reduction in conductance for heteromeric 8-G22R and 3 channels was greater than the reduction for homotypic 3 channels at V_j values. Smooth lines are fits to the Boltzmann equation whose parameters are given in Table 2. Consistent with the formation of heteromeric channels, co-expression of 8-G22R with wild-type 3 results in significantly altered gating properties.

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