SCAM analysis of the four TM segments of Panx1, with MBB as thiol reagent. The amino acids are arranged in ascending order for TM1 and TM3 and in descending order for TM2 and TM4 to reflect their directional orientation in the membrane. Means ± SE of irreversible current inhibition by 100 µM MBB are plotted. The number of oocytes analyzed is indicated on the right. NC, no channel activity was detected. *, P < 0.05; **, P < 0.01 (vs. Panx1 C426S control).