To infect a cell, an enveloped virus must first find a specific receptor protein studding the host cell's plasma membrane, lock onto it with its surface spike proteins, and then trigger membrane fusion — merging its own lipid envelope with the cell's membrane so its genome can slip into the cytoplasm. This scene stages that sequence: search, docking, receptor binding, fusion-pore formation, and genome release.
*Real membranes and viral particles are on a nanometre scale (a coronavirus spike is about 20nm tall); this simulation exaggerates size and slows every stage so the molecular choreography of entry is visible to the eye.
A spiked virus particle drifts toward a receptor-studded cell membrane, docks, locks onto a receptor, and drives membrane fusion so its genome can slip into the cytoplasm.
Receptor density and spike–receptor affinity control how quickly the virus finds and binds a receptor; protease priming controls how fast the fusion pore opens and the genome is released into the cell.
Adjust receptor density and binding affinity, toggle protease priming, and switch to the cutaway view to watch the fusion pore open through a cross-section of the membrane.
SARS-CoV-2's spike protein binds the ACE2 receptor, but many spikes must first be cleaved by a host protease such as TMPRSS2 before they can refold and pull the viral and cell membranes together.