1. Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
2. Synchrotron Research Center, Life Science Collaborative Access Team, Northwestern University, Argonne, Illinois 60439, United States
3. Center for Structural Biology, Vanderbilt University, Nashville, Tennessee 37232, United States
4. Vanderbilt-Ingram Cancer Center, Nashville, Tennessee 37232, United States