1. Department of Biochemistry; University of Washington, and Howard Hughes Medical Institute; Seattle Washington 98195
2. Research Center of Integrative Molecular Systems; Institute for Molecular Science, National Institute of Natural Sciences (NINS); Okazaki 444-8585 Japan
3. JST, PRESTO; Kawaguchi Saitama 332-0012 Japan
4. Department of Biological Science; Northeast Structural Genomics Consortium, Columbia University; New York New York