1. Department of Biochemistry, University of Washington, Seattle, WA 98195, USA.
2. Biomolecular Structure and Design Program, University of Washington, Seattle, WA 98195, USA.
3. Howard Hughes Medical Institute (HHMI), University of Washington, Seattle, WA 98195, USA.
4. Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA.
5. Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.