About the Authors
European Molecular Biology Laboratory, Heidelberg, Germany
Laboratory of Cellular and Structural Biology, The Rockefeller University, New York, New York, United States of America
The authors have declared that no competing interests exist.
The author(s) have made the following declarations about their contributions: Conceived and designed the experiments: RSM JF DPD. Performed the experiments: RSM JF AJ MG UB DPD. Analyzed the data: RSM JF AB IWM DPD. Contributed reagents/materials/analysis tools: AB IWM. Wrote the paper: RSM IWM DPD.