1. Department of Biochemistry, University of Wisconsin-Madison , Madison, WI 53706 , USA
2. Department of Chemistry, University of Wisconsin-Madison , Madison, WI 53706 , USA
3. Cryo-Electron Microscopy Research Center, University of Wisconsin-Madison , Madison, WI 53706 , USA
4. Midwest Center for Cryo-Electron Tomography, Department of Biochemistry, University of Wisconsin-Madison , Madison, WI 53706 , USA
5. Department of Chemistry and Biochemistry, Kalamazoo College , Kalamazoo, MI 49006 , USA
6. Neuroscience Training Program, University of Wisconsin-Madison , Madison, WI 53705 , USA
7. Department of Biology, Stanford University , Stanford, CA 94305 , USA
8. Department of Neuroscience, University of Wisconsin-Madison , Madison, WI 53705 , USA
9. Departments of Pediatrics and Biological Sciences, University of California, San Diego , La Jolla, CA 92093 , USA
10. Morgridge Institute for Research, University of Wisconsin-Madison , Madison, WI 53715 , USA