Figure 2

(a) Transmembrane topology and (b) conserved sequences of the ClC chloride channels. The topology of transmembrane helices 4-7 is currently unresolved; two models, based on conflicting experimental results [1,9], are indicated. Transmembrane helices 9-12 form an extensive, almost uninterrupted, hydrophobic region that crosses the membrane either three or five times. In (b), identical residues are shaded gray, and colors are as in (a).