Conformational changes required for H(+)/Cl(-) exchange mediated by a CLC transporter.

TitleConformational changes required for H(+)/Cl(-) exchange mediated by a CLC transporter.
Publication TypeJournal Article
Year of Publication2014
AuthorsBasilio D, Noack K, Picollo A, Accardi A
JournalNat Struct Mol Biol
Date Published2014 May
KeywordsBiological Transport, Chloride Channels, Crystallography, X-Ray, Escherichia coli K12, Escherichia coli Proteins, Models, Molecular, Mutation, Protein Structure, Tertiary

CLC-type exchangers mediate transmembrane Cl(-) transport. Mutations altering their gating properties cause numerous genetic disorders. However, their transport mechanism remains poorly understood. In conventional models, two gates alternatively expose substrates to the intra- or extracellular solutions. A glutamate was identified as the only gate in the CLCs, suggesting that CLCs function by a nonconventional mechanism. Here we show that transport in CLC-ec1, a prokaryotic homolog, is inhibited by cross-links constraining movement of helix O far from the transport pathway. Cross-linked CLC-ec1 adopts a wild-type-like structure, indicating stabilization of a native conformation. Movements of helix O are transduced to the ion pathway via a direct contact between its C terminus and a tyrosine that is a constitutive element of the second gate of CLC transporters. Therefore, the CLC exchangers have two gates that are coupled through conformational rearrangements outside the ion pathway.

Alternate JournalNat. Struct. Mol. Biol.
PubMed ID24747941
PubMed Central IDPMC4040230
Grant ListGM085232 / GM / NIGMS NIH HHS / United States
R01 GM085232 / GM / NIGMS NIH HHS / United States