1. Hartwell Center for Bioinformatics and Biotechnology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
2. Department of Infectious Diseases, Division of Virology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
3. Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
4. Department of Pathology, University of Tennessee Health Science Center, Memphis, TN 38163, USA.