Figure 5.

Electron cryo-tomograms of deformations in the liposomal membrane induced by interaction with virions at pH 5.5. Also see Supplementary Movies 1 and 2. (A) In this complex, the liposomal membrane appears to have been breached (white arrowhead, slice 1) at the contact zone where it is coordinated by HA spikes (black arrowheads, slice 1). Sample acidified for 5 min. Microscope defocus 3 μm. (B) In this tomogram, the liposome has been remodeled into a funnel that is apposed to the viral envelope; a putative opening at the funnel's mouth is indicated by the white arrowheads in slices 1 and 2. The virus envelope by contrast is intact. HA spikes (black arrowheads) ring the prefusion locus. Sample acidified for 8 min. Microscope defocus 5 μm; 5.3 nm virtual serial sections through the reconstructed tomograms are shown. Scalebars 50 nm.