title: Myotonia-related mutations in the distal C-terminus of ClC-1 and ClC-0 chloride channels affect the structure of a poly-proline helix.
abstract: Myotonia is a state of hyperexcitability of skeletal-muscle fibres. Mutations in the ClC-1 Cl- channel cause recessive and dominant forms of this disease. Mutations have been described throughout the protein-coding region, including three sequence variations (A885P, R894X and P932L) in a distal C-terminal stretch of residues [CTD (C-terminal domain) region] that are not conserved between CLC proteins. We show that surface expression of these mutants is reduced in Xenopus oocytes compared with wild-type ClC-1. Functional, biochemical and NMR spectroscopy studies revealed that the CTD region encompasses a segment conserved in most voltage-dependent CLC channels that folds with a secondary 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.
authors.affiliation: Institut de Recerca Biomédica, Parc Científic de Barcelona, Josep Samitier 1-5, Barcelona, E-08028, Spain.
authors.forename: María J
authors.initials: MJ
authors.lastname: Macías
authors.forename: Oscar
authors.initials: O
authors.lastname: Teijido
authors.forename: Giovanni
authors.initials: G
authors.lastname: Zifarelli
authors.forename: Pau
authors.initials: P
authors.lastname: Martin
authors.forename: Ximena
authors.initials: X
authors.lastname: Ramirez-Espain
authors.forename: Antonio
authors.initials: A
authors.lastname: Zorzano
authors.forename: Manuel
authors.initials: M
authors.lastname: Palacín
authors.forename: Michael
authors.initials: M
authors.lastname: Pusch
authors.forename: Raúl
authors.initials: R
authors.lastname: Estévez
mesh_terms: D000595:Amino Acid Sequence; D018118:Chloride Channels / Q000737:chemistry / Q000235:genetics*; D017124:Conserved Sequence; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D009222:Myotonia / Q000235:genetics*; D010449:Peptide Mapping; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation
chemical_list: C086321:CLC-1 channel; D018118:Chloride Channels; D010455:Peptides; C011083:polyproline