A novel coronavirus has recently been identified as the causative agent of SARS (Severe Acute Respiratory Syndrome). Coronaviruses are a major cause of upper respiratory diseases in humans. The genomes of these viruses are positive-stranded RNA approximately 27-31kb in length. The M protein (Membrane protein, Matrix protein) is one of the major structural viral proteins. It is an integral membrane protein involved in the budding of the viral particles and interacts with S (Spike) protein and the nucleocapsid protein. Coronaviruses have four important viral genes with different structural proteins: a spike glycoprotein (S), a small envelope protein (E), a matrix glycoprotein (M), and a nucleocapsid protein (N).