Seminal studies in the Carlier lab showed that pathogen-like propulsion could be reproduced in vitro with an appropriate cocktail containing actin, the Arp2/3 complex, N-WASP (or equivalent nucleator of Arp2/3), a capping protein and a severing protein (Loisel et al., 1999). Baculovirus bears at one end a surface receptor (p78/83) that activates the Arp2/3 complex and when the de-enveloped virus is incubated with a “motility cocktail” it induces actin comet tail formation at one end.
Comet tail induced by baculovirus in vitro and visualized in a conventional EM after negative staining.
Cryo-electron tomogram of actin comet formed in vitro in a mixture of baculovirus and the motility cocktail. Movie shows a scan in Z through the tomogram followed by a model of the filaments tracked in green and branch junctions in red.