1. Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Medicine, Tsinghua University, Beijing 100084, China.
2. Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA.
3. Advanced Photon Technology Division, Research Infrastructure Group, SR Life Science Instrumentation Unit, RIKEN/SPring-8 Center, 1-1-1 Kouto Sayo-cho Sayo-gun, Hyogo 679-5148, Japan.
4. Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.
5. Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.
6. Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, USA.
7. Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA.