Fig. 2. Voltage-gating properties of homotypic wild-type Cx50 channels and channels co-expressing Cx50-S50P and wild-type Cx50 subunits. (A,B) Junctional current was measured and plotted as a function of time, showing that channels co-expressing (B) both wild-type and mutant Cx50 proteins did not visibly alter current decay when compared with (A) homotypic Cx50 channels. (C) Analysis of channel closure kinetics. Representative current traces plotting the initial 250 mseconds of I_j recordings were fit to a monoexponential decay to determine the mean time constant . The co-expression of (C) wild-type and mutant Cx50 transcripts produce a mean value of 52 ms (n=5) a value significantly different (P<0.05, Student's t-test) from the 61 msecond mean channel closure time (n=4) exhibited by the homotypic wild-type channel during an 80 mV potential. I_j measurements recorded during a 120 mV voltage application show a significant decrease in the mean values from 34 mseconds for the (E) homotypic wild-type channel (n=4) to 25 ms shown by the (F) co-injected gap junctions (n=5, P<0.05, Student's t-test).