Chemical gating and single-channel conductance of Cx47 and Cx47-EGFP expressed in HeLa cells. A, B, Heptanol (2 mm) and CO₂ uncouple Cx47-EGFP homotypic junctions in transfected HeLa cells. Junctional currentI_j was measured by applying repeatedV_j steps to one cell of a pair.A, Application of heptanol (horizontal bar) to a cell pair in whichg_j = 10 nS produced full uncoupling and relatively fast recovery after washout. B, Application of 100% CO₂ (horizontal bar) to a cell pair with g_j = 13 nS fully uncoupled the cells within ∼20 sec, followed by slow recovery after washout. C, Illustration of Cx47 (top) and Cx47-EGFP (bottom) single-channel conductance and gating obtained in cell pairs during the early phase of recovery from full uncoupling with 100% CO₂ is shown. Records are of single-channel currents in response to repeated segments of ±17 mV, 200 msec V_j steps followed by ±65–85 mV, 2 sec V_j ramps. In both cases, a single-channel conductance of ∼55 pS and a substate conductance of ∼8 pS were approximated from the slopes of theI_j –V_j relations (solid and dashed lines, respectively).