Analysis of the Mechanosensor Channel Functionality of TACAN
- Howard Hughes Medical Institute, The Rockefeller University, United States
- Rockefeller University, United States
- The Rockefeller University, United States
Abstract
Mechanosensitive ion channels mediate transmembrane ion currents activated by mechanical forces. A mechanosensitive ion channel called TACAN was recently reported. We began to study TACAN with the intent to understand how it senses mechanical forces and functions as an ion channel. Using cellular patch-recording methods we failed to identify mechanosensitive ion channel activity. Using membrane reconstitution methods we found that TACAN, at high protein concentrations, produces heterogeneous conduction levels that are not mechanosensitive and are most consistent with disruptions of the lipid bilayer. We determined the structure of TACAN using single particle cryo-EM and observe that it forms a symmetrical dimeric transmembrane protein. Each protomer contains an intracellular-facing cleft with a coenzyme-A cofactor, confirmed by mass spectrometry. The TACAN protomers are related in 3-dimensional structure to a fatty acid elongase, ELOVL. Whilst its physiological function remains unclear, we anticipate that TACAN is not a mechanosensitive ion channel.
Data availability
The B-factor sharpened 3D cryo-EM density map and atomic coordinates of wild-type TACAN have been deposited in Worldwide Protein Data Bank (wwPDB) under accession codes 7N0K and EMD-24107.The B-factor sharpened 3D cryo-EM density map and atomic coordinates of His196Ala, His197Ala mutant TACAN have been deposited in Worldwide Protein Data Bank (wwPDB) under accession codes 7N0L and EMD-24108.
Article and author information
Author details
Roderick MacKinnon
Funding
National Institutes of Health (GM43949)
- Roderick MacKinnon
National Institutes of Health (GM109824)
- Brian Chait
National Institutes of Health (GM103314)
- Brian Chait
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Reviewing Editor
- Kenton J Swartz, National Institute of Neurological Disorders and Stroke, National Institutes of Health, United States
Version history
- Received: June 11, 2021
- Preprint posted: June 12, 2021 (view preprint)
- Accepted: August 6, 2021
- Accepted Manuscript published: August 10, 2021 (version 1)
- Version of Record published: August 19, 2021 (version 2)
Copyright
© 2021, Niu et al.
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.
Metrics
-
- 2,477
- views
-
- 351
- downloads
-
- 26
- citations
Views, downloads and citations are aggregated across all versions of this paper published by eLife.
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)
Analysis of the Mechanosensor Channel Functionality of TACAN
eLife 10:e71188.
https://doi.org/10.7554/eLife.71188
Further reading
-
- Structural Biology and Molecular Biophysics
The organization of nucleosomes into chromatin and their accessibility are shaped by local DNA mechanics. Conversely, nucleosome positions shape genetic variations, which may originate from mismatches during replication and chemical modification of DNA. To investigate how DNA mismatches affect the mechanical stability and the exposure of nucleosomal DNA, we used an optical trap combined with single-molecule FRET and a single-molecule FRET cyclization assay. We found that a single base-pair C-C mismatch enhances DNA bendability and nucleosome mechanical stability for the 601-nucleosome positioning sequence. An increase in force required for DNA unwrapping from the histone core is observed for single base-pair C-C mismatches placed at three tested positions: at the inner turn, at the outer turn, or at the junction of the inner and outer turn of the nucleosome. The results support a model where nucleosomal DNA accessibility is reduced by mismatches, potentially explaining the preferred accumulation of single-nucleotide substitutions in the nucleosome core and serving as the source of genetic variation during evolution and cancer progression. Mechanical stability of an intact nucleosome, that is mismatch-free, is also dependent on the species as we find that yeast nucleosomes are mechanically less stable and more symmetrical in the outer turn unwrapping compared to Xenopus nucleosomes.
-
- Cell Biology
- Structural Biology and Molecular Biophysics
Mutations in the human PURA gene cause the neurodevelopmental PURA syndrome. In contrast to several other monogenetic disorders, almost all reported mutations in this nucleic acid-binding protein result in the full disease penetrance. In this study, we observed that patient mutations across PURA impair its previously reported co-localization with processing bodies. These mutations either destroyed the folding integrity, RNA binding, or dimerization of PURA. We also solved the crystal structures of the N- and C-terminal PUR domains of human PURA and combined them with molecular dynamics simulations and nuclear magnetic resonance measurements. The observed unusually high dynamics and structural promiscuity of PURA indicated that this protein is particularly susceptible to mutations impairing its structural integrity. It offers an explanation why even conservative mutations across PURA result in the full penetrance of symptoms in patients with PURA syndrome.
