1. Department of Pharmaceutical Chemistry, University of CaliforniaSan Francisco, 600 16th Street, San Francisco, California 94143-2280, Department of Microbiology, University of Georgia, Athens, Georgia 30602, Departments of Biochemistry, Molecular and Medical Genetics, and Medical Biophysics, University of Toronto, Toronto, Ontario M5S 1A8, Canada, and Division of Cancer Genomics and Proteomics, Ontario Cancer Institute/Princess Margaret Hospital, Toronto, Ontario M5G 2M9, Canada