Coronavirus envelope protein

[2] In the beta and gamma groups, a conserved proline residue is found in the C-terminal region likely involved in targeting the protein to the Golgi.

[2] The transmembrane helices of the E proteins of SARS-CoV and SARS-CoV-2 can oligomerize and have been shown in vitro to form pentameric structures with central pores that serve as cation-selective ion channels.

[5] Both viruses' E protein pentamers have been structurally characterized by nuclear magnetic resonance spectroscopy.

[10] In others, including mouse coronavirus[11] and SARS-CoV, E is not essential, though its absence reduces viral titer,[12] in some cases by introducing propagation defects or causing abnormal capsid morphology.

[14] There is good evidence that E is involved in inducing membrane curvature to create the typical spherical coronavirus virion.

[17] The cation leakage may disrupt ion homeostasis, alter membrane permeability, and modulate pH in the host cell, which may facilitate viral release.

[3][18] In SARS-CoV, mutations that disrupt E's ion channel function result in attenuated pathogenesis in animal models despite little effect on viral growth.

Protein-protein interactions between E and proteins in the host cell are best described in SARS-CoV and occur via the C-terminal PDZ domain binding motif.

[21] The conserved nature of the envelope protein among SARS-CoV and SARS-CoV-2 variants has led it to be researched as a potential target for universal coronavirus vaccine development.

Solid-state NMR structure of the pentameric pore formed by the transmembrane helices of the SARS-CoV-2 E protein, which forms a viroporin permeable to cations . [ 5 ] [ 4 ] Rendered from PDB : 7K3G ​.
Illustration of a coronavirus virion in the respiratory mucosa , showing the positions of the four structural proteins and components of the extracellular environment [ 13 ]
The E viroporin opens at acid pH. The open state in pink presents a wide N-terminus. Conversely, the C-terminus narrows in the open state, which brings the polar sidechains of Thr35 and Arg38 close to the hydrophobic gate at Leu28. This presumedly lowers the energy barrier for ions to cross the channel.
Cryo-electron microscopy structure of the interaction between the SARS-CoV-2 E protein PDZ-binding motif (magenta) and a construct containing the PDZ (blue), SH3 (yellow), and guanylate kinase -like (GK, green) domains from a host cell protein, human PALS1 [ 19 ]