Single-channel SCAM indicates that G45 is a pore-lining residue. (A) Recordings of single G45C hemichannels in excised patches. The top trace is a recording from an inside-out patch held at −40 mV. Exposure to MTSET produced a stepwise reduction in current (discernable levels indicated by dashed lines). The bottom recording is from an outside-out patch held at 40 mV. Exposure to MTSES produced a stepwise increase in current (discernable levels indicated by dashed lines). C and O depict fully closed and open states in both traces. (B) Examples of G45C hemichannel currents before and after (3 min) application of MTS reagents. The left panel shows a single G45C hemichannel recording in the absence of added reagent. The solid line is a fit to the open hemichannel current. The middle and right panels show effects of MTS reagents. Solid black lines represent fits to the open hemichannel I-V relationships before MTS application. Data and fits (gray lines) are after MTS application. (C) Same as in B for single A40C hemichannels. All currents were elicited by 8-s voltage ramps between ±70 mV. Currents were leak subtracted as described in Materials and methods.