The following locations in the sequences of amino acid residues apply specifically to SARS-CoV-2. These vary somewhat with author, and the following are used here. The signal peptide (SP) comprises residues 1–19. On the inside of the lipid membrane, the carboxyl terminus (C-terminus) is comprised of the transmembrane region (TM) comprising residues 1214–1236 and the cytoplasmic tail (CT) residues1237-1273. The extracellular domain of the spike glycoprotein is comprised of N-terminal domain (S1-NTD) comprising residues 20–286, and is of particular interest here. The host cell receptor binding domain (RBD) comprising residues 319–541. In summary the key regions are as follows.SP 1-19
S1-NTD 20–286
RBD 319-541
S2 686-1213
TM 1214-1236
CT 1237-1273