1. QB3 Institute and Department of Molecular and Cell Biology, University of California–Berkeley, Berkeley, CA 94720, USA.
2. Division of Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
3. Department of Biochemistry, University of Washington, Seattle, WA 98195, USA.
4. Institute for Protein Design, Seattle, WA 98195, USA.
5. Howard Hughes Medical Institute, University of California–Berkeley, Berkeley, CA 94720, USA.