1. Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555-1019, USA
2. Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555-1019, USA
3. Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555-1019, USA
4. Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, Texas 77555, USA