1. Institute for Chemical Biology & Drug Discovery, Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400
2. Rocky Mountain Regional Center of Excellence and Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado 80523-1682
3. Center for Structural Biology, Stony Brook University, Stony Brook, New York 11794-5115
4. Rudolf Virchow Center for Experimental Biomedicine, Institute for Structural Biology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany