1. York Structural Biology Laboratory, University of York, Heslington, York YO10 5DD, U.K.
2. State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China
3. Department of Chemistry, Columbia University, New York, New York 10027, United States
4. Department of Systems Biology, Columbia University, New York, New York 10027, United States