Stepwise activation mechanism of the scramblase nhTMEM16 revealed by cryo-EMKalienkova, V., Mosina, V. C., Bryner, L., Oostergetel, G. T., Dutzler, R. & Paulino, C., 21-Feb-2019, In : eLife. 8, 27 p., 44364.
Research output: Contribution to journal › Article › Academic › peer-review
Scramblases catalyze the movement of lipids between both leaflets of a bilayer. Whereas the X-ray structure of the protein nhTMEM16 has previously revealed the architecture of a Ca2+-dependent lipid scramblase, its regulation mechanism has remained elusive. Here, we have used cryo-electron microscopy and functional assays to address this question. Ca2+-bound and Ca2+-free conformations of nhTMEM16 in detergent and lipid nanodiscs illustrate the interactions with its environment and they reveal the conformational changes underlying its activation. In this process, Ca2+ binding induces a stepwise transition of the catalytic subunit cavity, converting a closed cavity that is shielded from the membrane in the absence of ligand, into a polar furrow that becomes accessible to lipid headgroups in the Ca2+-bound state. Additionally, our structures demonstrate how nhTMEM16 distorts the membrane at both entrances of the subunit cavity, thereby decreasing the energy barrier for lipid movement.
|Number of pages||27|
|Publication status||Published - 21-Feb-2019|
- TMEM16A, PHOSPHATIDYLSERINE, VISUALIZATION, ORIENTATION, PROTEINS, EXPOSURE, CLONING, SYSTEM