Spike protein (S protein) is a highly glycosylated transmembrane protein. Spike proteins are assembled on the virus surface to form the distinctive "corona", or crown-like appearance. The S protein consists of two subunits, S1 and S2. The so-called ectodomain (ECD) is the part of the protein (S1+S2) which is located outside the virus membrane and expresses the epitopes that are accessible to antibodies.
Recombinant, expressed in Baculovirus