About the Authors
Institute of Structural Molecular Biology, University College London and Birkbeck College, London, United Kingdom
Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts, United States of America
Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
The authors have declared that no competing interests exist.
DV and EB performed the experiments. EB and GW designed the experiments. DV, EB, and GW wrote the paper. GW and SJH provided reagents.