1. Department
of Microbiology and Immunobiology, Harvard University, 77 Avenue
Louis Pasteur, Boston, Massachusetts 02115, United States
2. Department
of Chemistry and Chemical Biology, Harvard University, 12 Oxford
Street, Cambridge, Massachusetts 02138, United States
3. Division
of Infectious Diseases, Massachusetts General Hospital, 55 Fruit Street, Boston, Massachusetts 02114, United States
4. Department
of Biochemistry and Molecular Biology, Pennsylvania State University, 206
South Frear Laboratory, University Park, Pennsylvania 16802, United States