Figure 3
From: ClC chloride channels
A comparison between the molecular design of all known a-helical ion channel proteins and that of the ClC chloride channels, viewed from above the plane of the membrane. The conventional channels form pores between the symmetrically arranged subunits, along the axis of symmetry of the oligomer. Although the ClC channels have a two-fold axis of symmetry between the two ClC subunits, the pore is not on this axis; it is formed off-axis, within a single subunit, and hence with no symmetry.