1. Department of Pediatrics, Carver College of Medicine, University of Iowa, 25 South Grand Avenue, Iowa City, Iowa 52245, United States
2. Protein and Crystallography Facility, Carver College of Medicine, University of Iowa, 51 Newton Road, Iowa City, Iowa 52245, United States
3. Department of Pediatrics, University of Rochester, 601 Elmwood Avenue, Rochester, New York 14642, United States
4. Department of Biochemistry, University of Texas Southwestern, 5323 Harry Hines Boulevard, Dallas, Texas 75390, United States
5. Department of Biochemistry, Carver College of Medicine, University of Iowa, 51 Newton Road, Iowa City, Iowa 52245, United States
6. Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, 25 South Grand Avenue, Iowa City, Iowa 52245, United States