1. Department of Biological Sciences, Columbia University, New York, New York, USA
2. HHMI, Columbia University Medical Center, New York, New York, USA
3. Department of Biochemistry and Molecular Biophysics, Columbia University Medical Center, New York, New York, USA
4. Department of Microbiology and Immunology, Columbia University Medical Center, New York, New York, USA
5. Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia, USA