1. Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX 75235.
2. Department of Process Sciences, Genentech, Inc., South San Francisco, CA 94080.
3. Department of Medicinal and Analytical Chemistry, Genentech, Inc., South San Francisco, CA 94080.
4. Department of Molecular Biology, Genentech, Inc., South San Francisco, CA 94080.