1. Department of Biochemistry, University of Washington, Seattle, Washington 98195-7350, United States
2. Department of Biochemistry and Structural Biology, Centre for Molecular Protein Science, Chemical Centre, Lund University, PO Box 124, SE-22100 Lund, Sweden
3. Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, United States
4. Department of Molecular Biology and Biochemistry, Center for Advanced Biotechnology and Medicine, and Northeast Structural Genomics Consortium, Rutgers University, Piscataway, New Jersey 08854, United States
5. Howard Hughes Medical Institute, University of Washington, Seattle, Washington 98195-7350, United States