1. Department of Cell Biology and Molecular Genetics, University of Maryland , College Park, MD 20742, USA
2. Department of Chemistry and Biochemistry, University of Maryland , College Park, MD 20742, USA
3. CSSB – Centre for Structural Systems Biology , Deutsches Elektronen-Synchrotron (DESY), 22607 Hamburg , Germany
4. Christian-Albrechts-Universität , 24118 Kiel , Germany