1. Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
2. Faculty of Medicine, Health and Life Science, Swansea University, Swansea SA2 8PP, U.K.
3. Synchrotron Research Center, Life Science Collaborative Access Team, Northwestern University, Argonne, Illinois 60439, United States
4. Vanderbilt Institute of Chemical Biology, Nashville, Tennessee 37232, United States
5. Center for Structural Biology, Vanderbilt University, Nashville, Tennessee 37232, United States