Figure 1

Schematic of experimental strategy for separation of Env entry and stiffness activites. A WT immature particle (top) contains the full Env protein, including ectodomain and CT. Immature virions bearing ΔCT Env (middle left) retain viral entry activity, but lose particle stiffness, while immature particles bearing GFP-TM1 (middle right) lack any entry activity due to their missing Env ectodomain, but retain particle stiffness. Titration of GFP-TM1 into immature particles containing ΔCT Env (bottom) allows measurement of how increasing particle stiffness affects entry activity.