Myotonia-related mutations in the distal C-terminus of ClC-1 and ClC-0 chloride channels affect the structure of a poly-proline helix

structure containing a short type II poly-proline helix. We found that the myotonia-causing mutation A885P disturbs this structure by extending the poly-proline helix. We hypothesize that this structural modification results in the observed alteration of the common gate that acts on both pores of the channel. We provide the first experimental investigation of structural changes resulting from myotonia-causing mutations.