NMR Studies of the Q5A, G6S Unmyristylated Feline Immunodeficiency Virus Matrix Protein

Abstract

Feline Immunodeficiency Virus (FIV) has been identified as an animal model for studying Human Immunodeficiency Virus. The Gag polyprotein is targeted to the plasma membrane for viral budding via the matrix protein. A myristate group is covalently bound to the N-terminus of the matrix protein by the enzyme N-Myristyltransferase (NMT). Inhibitors targeted to the matrix protein have been proposed as possible drug treatments. The structure of myristylated FIV matrix protein is being solved using Nuclear Magnetic Resonance Spectroscopy (NMR).In order to myristylate FIV matrix with yeast NMT, mutations (Q5A, G6S) were introduced into the matrix gene. There is an interest, however, in comparing the unmyristylated mutant form of matrix with the unmyristylated wildtype form in order to evaluate the physiological relevance of the mutations. It is hypothesized that because only two residues of the protein were mutated, the overall three-dimensional fold of the mutant would be similar to the wildtype.To test this, FIV unmyristylated Q5A, G6S matrix protein was expressed, labeled with a 15N source, and purified. A Heteronuclear Single Quantum Coherence (HSQC) NMR experiment was performed and compared to HSQC spectra from the wildtype matrix protein. The comparison showed strong similarities between wildtype and mutant unmyristyalated FIV MA. The structures of FIV matrix and HIV matrix can be compared to determine the effectiveness of FIV as an animal model for drug trials.