Microscopically and as seen in the schematic figure below, coronaviruses have club-shaped trimeric surface spike glycoproteins that give the virions the appearance of a crown, hence their name (from the Latin corona meaning “crown”). Summarized in the table below, coronaviruses contain four major structural proteins: the spike (S), hemagglutinin-esterase (HE) in some betacoronaviruses, membrane (M), and envelope (E) all located on the membrane envelope, and the nucleocapsid (N) protein found in the core. The N proteins associate with the RNA genome to form a long helical ribonucleoprotein (RNP) packaged within the enveloped virus particle. The M protein, the most abundant of the structural proteins, is a transmembrane glycoprotein that gives the envelope its shape. The M protein embedded in the host membrane interacts with the N protein coating the viral RNA and thus helps assembly of enveloped virions. It serves as a “bridge” between the nucleocapsid and the other integral membrane proteins of the virus. The E protein is thought to be critical for coronavirus infectivity.