Retroviral matrix proteins (or major core proteins) are components of envelope-associated capsids, which line the inner surface of virus envelopes and are associated with viral membranes PMID:9657938. Matrix proteins are produced as part of Gag precursor polyproteins. During viral maturation, the Gag polyprotein is cleaved into major structural proteins by the viral protease, yielding the matrix (MA), capsid (CA), nucleocapsid (NC), 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. Although matrix proteins from different retroviruses appear to perform similar functions and can have similar structural folds, their primary sequences can be very different.

This entry represents matrix proteins from immunodeficiency lentiviruses, such as Human immunodeficiency virus (HIV) and Simian immunodeficiency virus (SIV-cpz) PMID:12465460. The structure of the HIV protein consists of 5 alpha helices, a short 3.10 helix and a 3-stranded mixed beta-sheet PMID:7966331.

PFAM:PF00540,INTERPRO:IPR000071