1. Department of Biochemistry, University of Wisconsin , Madison, WI , United States
2. Cryo-Electron Microscopy Research Center, Department of Biochemistry, University of Wisconsin , Madison, WI , United States
3. Midwest Center for Cryo-Electron Tomography, Department of Biochemistry, University of Wisconsin , Madison, WI , United States
4. Department of Chemistry, University of Wisconsin , Madison, WI , United States
5. Department of Biochemistry and Molecular Biology, University of Georgia , Athens, GA , United States
6. Max Planck Institute of Biochemistry , Martinsried , Germany
7. Morgridge Institute for Research , Madison, WI , United States