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. Department of Microbiology, Immunology and Physiology, Meharry Medical College, Nashville, Tennessee 37208, United States
4. Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, United States
5. Center for Structural Biology, Vanderbilt University, Nashville, Tennessee 37232, United States