Handbook of Ion Channels

of the channel pore such that helices B and J lie antiparallel on opposite sides of the triangular prism-shaped monomer. Helices Q and P fold back behind O, while H and I fold back behind G to make up the QPHI surface (most of the dimer interface) when viewed from the base of the prism. Crystal positions of the helix–helix linkers are uncertain for ClC-1 and are not drawn to scale but are generally indicative of their respective loop lengths. Importantly, CBS2 lies close to the cytoplasmic helix–helix loops and the linker between CBS2 and the poly-proline (PP) helix lies close to helix r and its linker to CBS1. the structures of the segments linking CBS1 to CBS2 and linking helix PP to the C terminus are quite unknown, as is the position of helix PP, although structural and functional studies (Macías et al., 2007; Feng et al., 2010; Ma et al., 2011) suggest that helix PP and the C terminus lie close to the cytoplasmic face of the membrane resident region of the monomer.