1. State Key Laboratory of Membrane Biology, Tsinghua University, Beijing 100084, China.
2. Tsinghua-Peking Joint Center for Life Sciences, Tsinghua University, Beijing 100084, China.
3. Center for Structural Biology, School of Life Sciences and School of Medicine, Tsinghua University, Beijing 100084, China.
4. National Institute of Biological Sciences, Beijing 102206, China.