1. Department of Biochemistry, Vanderbilt University, Nashville, TN 37240, USA.
2. Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA.
3. Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA.
4. Department of Pharmacology, Vanderbilt University, Nashville, TN 37240, USA.
5. Department of Bioinformatics, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
6. Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA.
7. Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA.