Fig. 3

Gc fusion loop unshielding and target membrane insertion. a A volumetric rendering is shown for tomographic reconstruction of purified RVFV virions and liposomes (M) incubated for ~30 s at pH 5.0. Surfaces of RVFV virions (V) were rendered by placing sub-tomogram averages of the virions back in the density. Scale bar, 100 nm. b A close-up of one virion sub-tomogram average with pentameric capsomers labelled (P) and showing a close interaction with the liposome membrane (M). The liposome membrane was rendered by placing sub-tomogram averages of liposome membrane back in the tomogram. Scale bar, 50 nm. c Sub-tomogram average of the pentamer at pH 5.0 with its apical densities embedded in the target liposome membrane (blue). Fitted X-ray structures of Gn and Gc are represented as ribbons and coloured as in Fig. 2. The fusion loop (FL) is in orange. Gn–Gc capsomers are rendered as a grey surface, viral membrane is in teal and liposome membranes are in light blue in a–c. The locations of the two leaflets in both the viral and the liposomal membrane are indicated with a dashed line. Unoccupied densities, assigned to C-terminal parts of the Gc and Gn glycoproteins that are absent from the fitted crystal structures, are indicated with asterisks. d Close-up of the inserted fusion loop. The liposome membrane is shown as a cartoon with lipid head groups in blue and hydrophobic tails in grey. The sub-tomogram average is shown as a mesh