1. Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA.
2. Department of Biochemistry, Vanderbilt University, Nashville, TN 37240, USA.
3. Division of Infectious Disease, Department of Pediatrics, Emory University School of Medicine, Atlanta, GA 30322, USA.
4. School of Biology, Georgia Institute of Technology, Atlanta, GA 30332, USA.
5. Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
6. Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
7. Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA.