Structural and functional characterization of an otopetrin family proton channel
- University of Texas Southwestern Medical Center, United States
Abstract
The otopetrin (OTOP) proteins were recently characterized as proton channels. Here we present the cryo-EM structure of OTOP3 from Xenopus tropicalis (XtOTOP3) along with functional characterization of the channel. XtOTOP3 forms a homodimer with each subunit containing 12 transmembrane helices that can be divided into two structurally homologous halves; each half assembles as an α-helical barrel that could potentially serve as a proton conduction pore. Both pores open from the extracellular half before becoming occluded at a central constriction point consisting of three highly conserved residues - Gln232/585-Asp262/Asn623-Tyr322/666 (the constriction triads). Mutagenesis shows that the constriction triad from the second pore is less amenable to perturbation than that of the first pore, suggesting an unequal contribution between the two pores to proton transport. We also identified several key residues at the interface between the two pores that are functionally important, particularly Asp509, which confers intracellular pH-dependent desensitization to OTOP channels.
Data availability
The cryo-EM density map of the XtOTOP3 has been deposited in the Electron Microscopy Data Bank under accession numbers EMDB-0650. Atomic coordinate has been deposited in the Protein Data Bank under accession number 6O84.
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Cryo-EM density map of OTOP3 from xenopus tropicalisElectron Microscopy Data Bank, EMD-0650.
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Atomic coordinates of OTOP3 from xenopus tropicalisProtein Data Bank, 6O84.
Article and author information
Author details
Funding
National Institute of General Medical Sciences (GM079179)
- Youxing Jiang
Howard Hughes Medical Institute
- Youxing Jiang
Welch Foundation (I-1578)
- Youxing Jiang
Cancer Prevention and Research Institute of Texas
- Xiaochen Bai
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2019, Chen 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.
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Structural and functional characterization of an otopetrin family proton channel
eLife 8:e46710.
https://doi.org/10.7554/eLife.46710
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