SARS (severe acute respiratory syndrome) is caused by a human coronavirus. Human coronaviruses are the major cause of upper respiratory tract illness, such as the common cold, in humans. Coronaviruses are positive-stranded RNA viruses, featuring the largest viral RNA genomes known to date (27-31 kb). The complete sequence of the SARS virus release the coronavirus contains 25 open reading frames. SARS-E2 glycoprotein precursor is a 139-kDa glycoprotein. It contains a superantigen between residues 690 through 1050 which has relationship to T-cell Receptor alpha-beta V chain protein.