Coronavirus Proteins

Coronaviruses are a group of enveloped, positive sense single-stranded RNA viruses that cause respiratory infections in mammals and birds, with symptoms varying from mild to fatal. The primary structural proteins of Coronaviruses are comprised of spike (S) glycoprotein, envelope (E) protein, membrane (M) protein, and nucleocapsid (N) protein. 

The Spike (S) glycoprotein is a transmembrane homotrimer with a molecular weight of about 150 kDa and is found on the outer surface of the viral envelope. Each monomer of the trimeric Spike protein contains two polypeptide subunits-S1 and S2, which mediates host cell attachment and membrane fusion respectively. In SARS-CoV-2, receptor binding domain (RBD) of the Spike protein is located in the C-terminus of S1 subunit and is responsible for the direct contact with ACE2 in host cells. Neutralizing antibodies against the receptor binding domain (RBD) and/or other regions of the Spike protein can prevent ACE2 binding and membrane fusion, thereby blocking viral entry into host cells.

The 3CL main protease (Nsp5), cleaves the sites of nonstructural proteins Nsp4-16 that are translated from the viral RNA.  Replication-essential enzymes such as RdRp or NSP13 are inactive without prior proteolytic release, positioning 3CL main protease as a key enzyme in the viral replication cycle and a promising drug target. Find these and other proteins below.