1. Department of Biochemistry and Molecular Biology, Center for Structural Biology, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida, USA
2. Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
3. Cryo-EM Core Facility, University of Massachusetts Medical School, Worcester, Massachusetts, USA
4. Biological Science Imaging Resource, Department of Biological Sciences, Florida State University, Tallahassee, Florida, USA
5. Department of Virology, University of Helsinki, Helsinki, Finland