E glycoproteins are small proteins that are composed of approximately 76 to 109 amino acids. About 30 amino acids in the N-terminus of the E proteins allow attachment to the membrane of viruses. In addition, coronavirus E proteins play a critical role in the assembly and morphogenesis of virions within the cell. In one study coronavirus E and M proteins were expressed together with mammalian expression vectors to form virus-like structures within the cell. In another study, there was a significant decrease in the abikity of the recombinant mouse hepatitis virus (MHV) and SARS viruses to elicit E protein expression in the genome to support this status.