Retroviral matrix proteins are components of envelope-associated capsids of retroviruses. These proteins line the inner surface of viral envelopes and are associated with viral membranes.[1]
Matrix proteins are produced as N-terminal domains of Gag precursor polyproteins. The Gag polyprotein directs the assembly and release of virus particles from infected cells. The Gag polyprotein has three domains required for activity: an N-terminal membrane-binding (M) domain (which corresponds to the matrix protein) that directs Gag to the plasma membrane, an interaction (I) domain involved in Gag aggregation, and a late assembly (L) domain that mediates the budding process .[2] During viral maturation, the Gag polyprotein is cleaved by the retroviral protease into several corresponding structural proteins, yielding the matrix (MA), capsid (CA), and nucleocapsid (NC) proteins, and some smaller peptides. Gag-derived proteins govern the entire assembly and release of the virus particles, with matrix proteins playing key roles in Gag stability, capsid assembly, transport and budding.