1. Department of Microbiology and Molecular Genetics, School of Medicine, University of Pittsburgh, 450 Technology Drive, Pittsburgh, Pennsylvania 15219, United States
2. Department of Structural Biology, School of Medicine, University of Pittsburgh, 3501 Fifth Avenue, Pittsburgh, Pennsylvania 15260, United States
3. Department of Infectious Disease Research, Drug Development Division, Southern Research Institute, 431 Aviation Way, Frederick, Maryland 21701, United States