1. University of Oxford, Department of Biochemistry, Laboratory of Molecular Biophysics, South Parks Road, Oxford OX1 3QU, UK.
2. Structural Biology Division, The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3050, Australia.
3. University of Oxford, University Laboratory of Physiology, Parks Road, Oxford OX1 3PT, UK.
4. Department of Microbiology and Bioinformatics, Gifu University Graduate School of Medicine, Regeneration, and Advanced Medical Science, 40 Tsukasamachi, Gifu 500-8705, Japan.