The 3.0 Å cryo-EM structure we present here delineates the tripartite epitope of 11886 down the arête of the GP chalice, bridging and pinning together the GP2 N-terminus, GP1 core and the GC into a pre-fusion conformation, thereby likely preventing the rearrangements required for receptor binding, membrane fusion and infection. Here, GTPBP1 is linked to infection.