Two positively charged amino acid side-chains in the inner vestibule of the CFTR channel pore play analogous roles in controlling anion binding and anion conductance

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Résumé

Positively charged amino acid side-chains play important roles in anion binding and permeation through the CFTR chloride channel. One pore-lining lysine residue in particular (K95) has been shown to be indispensable for anion binding, conductance, and selectivity. Here, we use functional investigation of CFTR to show that a nearby arginine (R134) plays a functionally analogous role. Removal of this positive charge (in the R134Q mutant) drastically reduces single-channel conductance, weakens binding of both permeant and blocking anions, and abolishes the normal anion conductance selectivity pattern. Each of these functional effects was reversed by a second-site mutation (S1141K) that introduces an ectopic positive charge to a nearby pore-lining residue. Substituted cysteine accessibility experiments confirm that R134—but not nearby residues in the same transmembrane helix—is accessible within the pore lumen. These results suggest that K95 and R134, which are very close together within the inner vestibule of the pore, play analogous, important roles, and that both are required for the normal anion binding and anion conductance properties of the pore. Nevertheless, that fact that both positive charges can be “transplanted” to other sites in the inner vestibule with little effect on channel permeation properties indicates that it is the overall number of charges—rather than their exact locations—that controls pore function.

Langue d'origineEnglish
Pages (de-à)5213-5223
Nombre de pages11
JournalCellular and Molecular Life Sciences
Volume78
Numéro de publication12
DOI
Statut de publicationPublished - juin 2021

Note bibliographique

Funding Information:
This work was supported by a grant from the Natural Sciences and Engineering Research Council of Canada (RGPIN/05124–2017).

Publisher Copyright:
© 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG.

ASJC Scopus Subject Areas

  • Molecular Medicine
  • Molecular Biology
  • Pharmacology
  • Cellular and Molecular Neuroscience
  • Cell Biology

PubMed: MeSH publication types

  • Journal Article

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