1. NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Frederick, Maryland 21701, United States
2. Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, 1450 3rd Street, San Francisco, California 94158, United States
3. Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, Maryland 21702, United States