1. Laboratory of Molecular Immunology, The Rockefeller University, New York, NY 10065, USA.
2. Laboratory of Retrovirology, The Rockefeller University, New York, NY 10065, USA.
3. Laboratory of Virology and Infectious Disease, The Rockefeller University, New York, NY 10065, USA.
4. Structural Biology Resource Center, The Rockefeller University, New York, NY 10065, USA.
5. Institute for Research in Biomedicine, Università della Svizzera italiana, 6500 Bellinzona, Switzerland.
6. Howard Hughes Medical Institute, The Rockefeller University, New York, NY 10065, USA.