S (spike) glycoprotein: This large protein made up of smaller subunits plays an important role in the transmission process – it attaches to a molecule called a receptor on the human cell so the virus can infect it. S proteins cover the outside of the virus – they are embedded in a lipid bilayer. M (membrane) protein: Membrane proteins, visualized in our model in green, are diffusely present on the virus surface, but had not yet been mapped at the time of our research. We decided to use a very simple substitute model for this, similar to the N protein. HE (hemagglutinin esterase) protein Hemagglutinin esterase is a glycoprotein on the surface of the virus that some enveloped viruses, including some Coronaviruses, use as invasion mechanism. HEs are responsible for several important functions in genome maintenance and virus replication. They help the virus attach to and destroy certain sialic acid receptors found on the host cell surface. The HE protein carries out several enzyme activities, including receptor binding, receptor hydrolysis and membrane fusion.
E (envelope) protein: The third protein that makes up the viral envelope, or outer layer, is the envelope protein. This had also not been mapped at the time of our research, so we decided to use a very simple substitute model. N (nucleocapsid) protein: N proteins bind to the virus’s RNA (its genetic material, visualized in red) to help organize and protect it. The host cell translates viral RNA into new viral proteins, some of which are assembled into new copies of the virus, which then continue the cycle by infecting other cells. The N proteins have different orientations, relative to each other and relative to the disordered amino acid strings of the RNA. Since this orientation is still not entirely clear, and given the technical challenge and time limitations for this animation, we applied some artistic license when it came to their organization around the RNA chain.
We wanted our animation peak point to be the moment at which the S protein binds to the host ACE2 cellular receptor of a lung cell. By binding to this specific receptor, the virus makes its way into the cell, starting the infection. For the rendering, we imagined the animation to play out against a warm, pinkish background. We chose this as it could help the viewer imagine the tissues inside the human body, where the virus infects cells. Before settling on this background, we tried other options. We hope you like the animation! Please feel free to provide your contribution should any of the content be revised.