During the ongoing SARS outbreak, it has been discovered that the novel virus has developed a new viral entry mechanism by binding S protein to angiotensin-converting enzyme 2 (ACE2) receptors (Li et al., 2003), as the identification mark of SARS-CoV adaptation which has been caused by the mutations on S protein residues between 318–510 that named as receptor binding protein (RBD) (Wong et al., 2004; Li et al., 2005). The gene discussed is PROS1; the disease is severe acute respiratory syndrome.