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

María J Macías , Oscar Teijido , Giovanni Zifarelli , Pau Martin , Ximena Ramirez-Espain , Antonio Zorzano , Manuel Palacín , Michael Pusch , Raúl Estévez , Raúl Estévez (1)

1 Biochemistry and Molecular Biology

Myotonia is a state of hyperexcitability of skeletal muscle fibers. 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, P932L) in a distal C-terminal stretch of residues (CTD region) that are not conserved between CLC proteins. We show that surface expression of these mutants is reduced in Xenopus oocytes compared to 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.

Mots clés: Life Sciences

María J Macías, Oscar Teijido, Giovanni Zifarelli, Pau Martin, Ximena Ramirez-Espain, et al.. Myotonia-related mutations in the distal C-terminus of ClC-1 and ClC-0 chloride channels affect the structure of a poly-proline helix. Biochemical Journal, 2006, 403 (1), pp.79-87. ⟨10.1042/BJ20061230⟩. ⟨hal-00478648⟩