Fig. 5.

Gap junction channels formed by growth-arresting isoforms of Cx37 prefer the closed state. (A–C) Representative single-channel traces from the indicated genotypes suggesting that Cx37-S319D and -WT prefer the closed state whereas Cx37-S319A prefers a 60–120 pS substate. For the Cx37-WT and -S319A traces, only one channel is active and its closed state corresponds to the 0 pS line indicated by long dashes. For the Cx37-S319D trace, three channels are open at the start of the pulse (652 pS); their successive stable closures result in the peaks at 440 pS (2 channels open) and 192 pS (1 channel open). The size of observed transitions is shown on the left of each trace; all-points histograms, on the right, indicate the frequency of each conductance state for the illustrated trace. ↓ and ↑ indicate polarity and onset/end of pulse in the partner cell. (D) Relative mean±s.e.m. transition frequencies for all three Cx37 isoforms showing transitions between multiple open states and a closed state, including fully open to closed. Together the traces and histogram suggest Cx37-WT channels frequently transition between the ∼90 pS substate and the closed state [traces and previously published studies (Jacobsen et al., 2017) suggest the closed state is preferred]. The Cx37-S319D channels close frequently from multiple open states, but most commonly from the ∼200 pS conductance state (traces suggest closed state is preferred over the many open states). Cx37-WT: n=17, event no.=1917; Cx37-S319A: n=12, event no.=1280; Cx37-S319D: n=20, event no.=4493.