The authors are grateful to members of the Kranzusch laboratory for helpful comments and discussion. The work was funded by grants to P.J.K. from the Pew Biomedical Scholars programme, the Burroughs Wellcome Fund PATH programme, The G. Harold and Leila Y. Mathers Charitable Foundation, The Mark Foundation for Cancer Research, the Cancer Research Institute, the Parker Institute for Cancer Immunotherapy, the Massachusetts Consortium on Pathogen Readiness (MassCPR), and the National Institutes of Health (1DP2GM146250-01), S.Y. is supported by a JSPS Overseas Research Fellowships (202360072) and a Human Frontiers Science Program Long-Term Fellowship (LT0051). D.R.W. is supported through a Helen Hay Whitney Foundation postdoctoral fellowship. S.G.F. is supported through a Cancer Research Institute Irvington Postdoctoral Fellowship (CRI14458). X-ray data were collected through support by an agreement between the Advanced Photon Source, a US Department of Energy (DOE) Office of Science user facility operated for the DOE Office of Science by Argonne National Laboratory under contract no. DE-AC02-06CH11357, and the Diamond Light Source, the national synchrotron science facility of the UK, located at the Harwell Science and Innovation Campus in Oxfordshire; at the Advanced Photon Source through the Northeastern Collaborative Access Team beamlines, which are funded by the National Institute of General Medical Sciences from the National Institutes of Health (P30 GM124165) and a NIH-ORIP HEI grant (S10OD021527); and at The Center for Bio-Molecular Structure (CBMS) that is primarily supported by the NIH-NIGMS through a Center Core P30 Grant (P30GM133893), and by the DOE Office of Biological and Environmental Research (KP1607011). NSLS2 is a US DOE Office of Science User Facility operated under Contract No. DE-SC0012704. Cryo-EM data were collected at the Harvard Cryo-EM Center for Structural Biology at Harvard Medical School. ITC data were collected at the Center for Macromolecular Interactions at Harvard Medical School CMI (RRID: SCR_018270).