Structure of Myristoylated Matrix Protein of Mason-Pfizer Monkey Virus and the Role of Phosphatidylinositol-(4,5)-bisphosphate in its Membrane Binding

Jan Prchal^1,2, Tomas Ruml¹, Richard Hrabal²

¹Department of Biochemistry and Microbiology, Institute of Chemical Technology, Technická 5, 166 28 Prague 6, Czech Republic

²Laboratory of NMR Spectroscopy, Institute of Chemical Technology, Technická 5, 166 28 Prague 6, Czech Republic

richard.hrabal@vscht.cz

During the late phase of the Mason-Pfizer Monkey Virus (M-PMV) life-cycle, its immature virus particles are transported to the plasma membrane and bud out of a cell. Binding to the membrane is facilitated by an N-terminal domain of Gag, the matrix protein (MA), which is N-terminally myristoylated. Structural studies on HIV-1 and HIV-2 MAs have proven that the myristoyl serves as an anchor in the membrane, but while MA is in an unbound state the myristoyl is sequestered in MA. The change between these two states is called a myristoyl-switch. Saad at al. reported that the myristoyl-switch of HIV-1 MA is triggered by a phosphatidylinositol-4,5bisphosphate (PIP), which is a phospholipid found exclusively at cytoplasmic membrane.

We used NMR spectroscopy to determine the structure of myristoylated M-PMV MA and to observe its interaction with PIP. The structure of myristoylated M-PMV MA is generally similar to the structure of nonmyristoylated M-PMV MA, but shows some differences mainly in the orientation of the first helix and in its C-terminal part. The myristoyl is sequestered deeper than in HIV-1 MA. PIP interacts with myristoylated M-PMV MA. It binds to a similar part of M-PMV MA as to HIV-1 MA, but the interaction is weaker and PIP with shorter fatty-acid chains is not sufficient to trigger the myristoyl-switch. These results show that M-PMV MA interacts with the membrane in a similar way as HIV-1 MA, but shows some significant differences that can be contributed to distinctions in the life-cycle of these retroviruses.