N-Glycans modulate tilting of HIV-1 envelope glycoprotein.

Human immunodeficiency virus-1 (HIV-1) remains a global health crisis, with over 40 million people living with the virus and no effective vaccine available. Central to HIV infection and immune evasion is the envelope glycoprotein (Env), a heavily glycosylated class I fusion protein that mediates viral entry and is the sole immunogenic target. Despite the recent advancements provided by imaging techniques, the characterization of Env's structure and dynamics within its native membrane environment remains incomplete. Here, we present microsecond-long, all-atom molecular dynamics simulations of the full-length, glycosylated Env glycoprotein embedded in a biologically relevant lipid bilayer. Our simulations, corroborated by cryo-electron tomography, reveal a pronounced tilting motion of Env relative to the membrane. Importantly, we identify a critical role for N-linked glycans at N88 and N611 in modulating the transition to tilted conformations. Alongside illuminating the sites of vulnerability within the glycan shield, the results presented here underscore Env tilting dynamics as a feature that can be leveraged in immunogen design.