1. Molecular Structure & Function, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
2. Department
of Structural Biology, St. Jude Children’s Research Hospital, Memphis, Tennessee 38105, United States
3. Department
of Microbiology, Immunology and Biochemistry, University of Tennessee Health Sciences Center, Memphis, Tennessee 38163, United States
4. Department
of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada