Molecular pathology of the R117H cystic fibrosis mutation is explained by loss of a hydrogen bond

  1. Márton A Simon
  2. László Csanády  Is a corresponding author
  1. Semmelweis University, Hungary


The phosphorylation-activated anion channel CFTR is gated by an ATP hydrolysis cycle at its two cytosolic nucleotide binding domains, and is essential for epithelial salt-water transport. A large number of CFTR mutations cause cystic fibrosis. Since recent breakthrough in targeted pharmacotherapy, CFTR mutants with impaired gating are candidates for stimulation by potentiator drugs. Thus, understanding the molecular pathology of individual mutations has become important. The relatively common R117H mutation affects an extracellular loop, but nevertheless causes a strong gating defect. Here we identify a hydrogen bond between the side chain of arginine 117 and the backbone carbonyl group of glutamate 1124 in the cryo-electronmicroscopic structure of phosphorylated, ATP-bound CFTR. We address the functional relevance of that interaction for CFTR gating using macroscopic and microscopic inside-out patch-clamp recordings. Employing thermodynamic double-mutant cycles, we systematically track gating-state dependent changes in the strength of the R117-E1124 interaction. We find that the H-bond is formed only in the open state, but neither in the short-lived "flickery" nor in the long-lived 'interburst' closed state. Loss of this H-bond explains the strong gating phenotype of the R117H mutant, including robustly shortened burst durations and strongly reduced intraburst open probability. The findings may help targeted potentiator design.

Data availability

All data generated or analysed during this study are included in the main text figures, tables, and supporting figures.

Article and author information

Author details

  1. Márton A Simon

    Department of Biochemistry, Semmelweis University, Budapest, Hungary
    Competing interests
    No competing interests declared.
  2. László Csanády

    Department of Biochemistry, Semmelweis University, Budapest, Hungary
    For correspondence
    Competing interests
    László Csanády, Reviewing editor, eLife.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-6547-5889


European Union (Horizon 2020 Research and Innovation Program,739593)

  • László Csanády

Magyar Tudományos Akadémia (Lendület Award,LP2017-14/2017)

  • László Csanády

Cystic Fibrosis Foundation (Research Grant,CSANAD21G0)

  • László Csanády

Ministry for Innovation and Technology (New National Excellence Program,ÚNKP-20-3-I-SE-34)

  • Márton A Simon

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.


Animal experimentation: This study was performed in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. All of the animals were handled according to approved institutional animal care and use committee (IACUC) protocols of Semmelweis University (last approved 06-03-2021, expiration 06-03-2026).

Reviewing Editor

  1. Andrés Jara-Oseguera, The University of Texas at Austin, United States

Version history

  1. Received: October 13, 2021
  2. Preprint posted: October 21, 2021 (view preprint)
  3. Accepted: December 3, 2021
  4. Accepted Manuscript published: December 6, 2021 (version 1)
  5. Version of Record published: December 15, 2021 (version 2)


© 2021, Simon & Csanády

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.


  • 1,996
    Page views
  • 153
  • 7

Article citation count generated by polling the highest count across the following sources: Crossref, PubMed Central, Scopus.

Download links

A two-part list of links to download the article, or parts of the article, in various formats.

Downloads (link to download the article as PDF)

Open citations (links to open the citations from this article in various online reference manager services)

Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)

  1. Márton A Simon
  2. László Csanády
Molecular pathology of the R117H cystic fibrosis mutation is explained by loss of a hydrogen bond
eLife 10:e74693.

Share this article

Further reading

    1. Structural Biology and Molecular Biophysics
    Fouad Ouasti, Maxime Audin ... Francoise Ochsenbein
    Research Article

    Genome and epigenome integrity in eukaryotes depends on the proper coupling of histone deposition with DNA synthesis. This process relies on the evolutionary conserved histone chaperone CAF-1 for which the links between structure and functions are still a puzzle. While studies of the Saccharomyces cerevisiae CAF-1 complex enabled to propose a model for the histone deposition mechanism, we still lack a framework to demonstrate its generality and in particular, how its interaction with the polymerase accessory factor PCNA is operating. Here, we reconstituted a complete SpCAF-1 from fission yeast. We characterized its dynamic structure using NMR, SAXS and molecular modeling together with in vitro and in vivo functional studies on rationally designed interaction mutants. Importantly, we identify the unfolded nature of the acidic domain which folds up when binding to histones. We also show how the long KER helix mediates DNA binding and stimulates SpCAF-1 association with PCNA. Our study highlights how the organization of CAF-1 comprising both disordered regions and folded modules enables the dynamics of multiple interactions to promote synthesis-coupled histone deposition essential for its DNA replication, heterochromatin maintenance, and genome stability functions.

    1. Chromosomes and Gene Expression
    2. Structural Biology and Molecular Biophysics
    Matthew R Marunde, Harrison A Fuchs ... Catherine A Musselman
    Research Article Updated

    Histone post-translational modifications (PTMs) play a critical role in chromatin regulation. It has been proposed that these PTMs form localized ‘codes’ that are read by specialized regions (reader domains) in chromatin-associated proteins (CAPs) to regulate downstream function. Substantial effort has been made to define [CAP: histone PTM] specificities, and thus decipher the histone code and guide epigenetic therapies. However, this has largely been done using the reductive approach of isolated reader domains and histone peptides, which cannot account for any higher-order factors. Here, we show that the [BPTF PHD finger and bromodomain: histone PTM] interaction is dependent on nucleosome context. The tandem reader selectively associates with nucleosomal H3K4me3 and H3K14ac or H3K18ac, a combinatorial engagement that despite being in cis is not predicted by peptides. This in vitro specificity of the BPTF tandem reader for PTM-defined nucleosomes is recapitulated in a cellular context. We propose that regulatable histone tail accessibility and its impact on the binding potential of reader domains necessitates we refine the ‘histone code’ concept and interrogate it at the nucleosome level.