Fig. 1. Effect of DIDS on KCNQ1 channels depends on the presence of KCNE1. A. Structural depiction of 4,4'-Diisothiocyanato-2,2'-stilbenedisulfonic acid (DIDS) as structural formula and as space fill representation (CPK coloring). The symmetric structure of DIDS contains two aromatic benzyl rings, two outer amides and two sulfonic groups. The molecule thus combines aromatic regions with charged regions. B. Representative current traces of KCNQ1 or KCNQ1/KCNE1 expressed at a ratio of 1 to 2 recorded in Xenopus laevis oocytes before (black) and after (gray) application of 10 µM DIDS.