Envelope glycoprotein mobility on HIV-1 particles depends on the virus maturation state
Chojnacki J., Waithe D., Carravilla P., Huarte N., Galiani S., Enderlein J., Eggeling C.
Human Immunodeficiency Virus (HIV-1) assembles as immature particles which require the proteolytic cleavage of structural polyprotein Gag and the clustering of envelope glycoprotein Env for infectivity. The details of mechanisms underlying Env clustering remain unknown. Here we determine molecular dynamics of Env on the surface of individual HIV-1 particles using scanning Fluorescence Correlation Spectroscopy on a super-resolution STED microscope (sSTED-FCS). We find that Env undergoes a maturation-induced increase in mobility, highlighting diffusion as one cause for Env clustering. This mobility increase is dependent on Gag-interacting Env tail but not on changes in viral envelope lipid order. Diffusion of Env and other envelope incorporated proteins in mature HIV-1 is two orders of magnitude slower than in the plasma membrane, indicating that HIV-1 envelope is intrinsically a low mobility environment, mainly due to its high lipid order. Our results provide novel insights into dynamic properties of proteins on the surface of individual virus particles.