1. Z. Songyang, J. Xu, L. C. Cantley, Division of Signal Transduction, Beth Israel Hospital, and Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
2. A. S. Fanning and J. M. Anderson, Departments of Internal Medicine and Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA.
3. C. Fu and A. C. Chan, Howard Hughes Medical Institute, Center for Immunology, Department of Medicine and Pathology, Washington University School of Medicine, St. Louis, MO 63110, USA.
4. S. M. Marfatia and A. H. Chishti, Laboratory of Tumor Cell Biology, Department of Biomedical Research, St. Elizabeth's Medical Center, Tufts University, Boston, MA 02135, USA.
5. A. Crompton, ONYX Pharmaceuticals, 3031 Research Drive, Building A, Richmond, CA 94806, USA.