Affiliation: | 1Department of Microbiology, Immunology, and Molecular Genetics, and the Molecular Biology Institute, University of California, and the David Geffen School of Medicine, Los Angeles, California 90095;2Department of Microbiology, Columbia University Medical Center, New York, New York 10032;3Department of Biochemistry and Molecular Biophysics, Columbia University Medical Center, New York, New York 10032 |