1. MOE Key Laboratory of Protein Science, Tsinghua University, Beijing 100084, P.R. China.
2. School of Life Science, Tsinghua University, Beijing 100084, P.R. China.
3. Peking University–Tsinghua University–National Institute of Biological Sciences Joint Graduate Program, Beijing 100084, China.
4. Howard Hughes Medical Institute and Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, UT 84112, USA.
5. State Key Laboratory of Membrane Biology, Peking-Tsinghua Joint Center for Life Sciences, School of Life Sciences, Peking University, Beijing 100871, China.
6. Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing 100084, China.