Cryo-EM structures and functional characterization of the murine lipid scramblase TMEM16F
The lipid scramblase TMEM16F initiates blood coagulation by catalyzing the exposure of phosphatidylserine in platelets. The protein is part of a family of membrane proteins, which encompasses calcium-activated channels for ions and lipids. Here, we reveal features of murine TMEM16F (mTMEM16F) that underlie its function as a lipid scramblase and an ion channel. The cryo-EM data of mTMEM16F in absence and presence of Ca2+ define the ligand-free closed conformation of the protein and the structure of a Ca2+-bound intermediate. Both conformations resemble their counterparts of the scrambling-incompetent anion channel mTMEM16A, yet with distinct differences in the region of ion and lipid permeation. In conjunction with functional data, we demonstrate the relationship between ion conduction and lipid scrambling. Although activated by a common mechanism, both functions appear to be mediated by alternate protein conformations that are at equilibrium in the ligand-bound state.
The three-dimensional cryo-EM density maps as well as the modelled coordinated will be deposited in the Electron Microscopy Data Bank and the Protein Data Bank, respectively. The deposition includes the cryo-EM maps, both half-maps, and the mask used for final FSC calculation. The raw data can be provided upon request.
Cryo-EM structure of calcium-bound mTMEM16F lipid scramblase in digitoninElectron Microscopy Data Bank, EMD-4611.
Cryo-EM structure of calcium-free mTMEM16F lipid scramblase in digitoninElectron Microscopy Data Bank, EMD-4612.
Cryo-EM structure of calcium-bound mTMEM16F lipid scramblase in nanodiscElectron Microscopy Data Bank, EMD-4613.
Cryo-EM structure of calcium-free mTMEM16F lipid scramblase in nanodiscElectron Microscopy Data Bank, EMD-4614.
Article and author information
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (740.018.016)
- Cristina Paulino
H2020 European Research Council (339116)
- Raimund Dutzler
H2020 European Research Council (AnoBest)
- Raimund Dutzler
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
- Kenton Jon Swartz, National Institute of Neurological Disorders and Stroke, National Institutes of Health, United States
- Received: December 12, 2018
- Accepted: February 19, 2019
- Accepted Manuscript published: February 20, 2019 (version 1)
- Version of Record published: March 12, 2019 (version 2)
© 2019, Alvadia 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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