The three-dimensional solution structure of the matrix protein from the type D retrovirus, the Mason-Pfizer monkey virus, and implications for the morphology of retroviral assembly

The Mason-Pfizer monkey virus (M-PMV) is the prototype of the type D retroviruses. In type B and D retroviruses, the Gag protein pre-assembles before association with the membrane, whereas in type C retroviruses (lentiviruses, BLV/HTLV group) Gag is targeted efficiently to the plasma membrane, where the particle formation occurs, The N-terminal domain of Gag, the matrix protein (MA), plays a critical role in determining this morphogenic difference, We have determined the three-dimensional solution structure of the M-PMV MA by heteronuclear nuclear magnetic resonance, The protein contains four alpha-helices that are structurally similar to the known type C MA structures, This similarity implies possible common assembly units and membrane-binding mechanisms for type C and BID retroviruses. In addition to this, the interpretation of mutagenesis data has enabled us to identify, for the first time, the structural basis of a putative intracellular targeting moth.