1. Department of Biochemistry, University of Washington, Seattle, WA 98105, USA.
2. Institute for Protein Design, University of Washington, Seattle, WA 98105, USA.
3. Paul G. Allen School of Computer Science and Engineering, University of Washington, Seattle, WA 98105, USA.
4. Graduate Program in Biological Physics, Structure and Design, University of Washington, Seattle, WA 98105, USA.
5. Howard Hughes Medical Institute, University of Washington, Seattle, WA 98105, USA.
6. School of Biosciences, University of Sheffield, Sheffield S10 2TN, UK.
7. School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea.