INTERACTION OF THE N-TERMINAL MYRISTIC ACID WITH MATRIX PROTEIN FROM MASON-PFIZER MONKEY VIRUS.

 

Jan Prchal1, Michal Dolezal1, Jiri Vlach1, Jan Lipov1, Michaela Rumlova2, Eric Hunter3, Tomas Ruml1, Richard Hrabal1

 

1Institute of Chemical Technology in Prague, Prague, Czech Republic; 2Institute of Organic chemistry and Biochemistry, Prague, Czech Republic; 3Emory Vaccine Center at Yerkes Nat. Primate Res.C., Atlanta, USA

 

Polyprotein Gag as a precursor of structural proteins plays a key role in formation and budding of retroviral particles. The N-terminal domain of Gag, the matrix protein (MA) interacts with the cytoplasmic membrane of infected cell through the bipartite signal that involves a cluster of basic residues and myristic acid which is covalently attached to the amino-terminal glycine.

In this work we focus on the determination of molecular basis of the phenotypic changes of M-PMV double-mutants T41I/T78I and Y28F/Y67F, which are unable to bud through the cytoplasmic membrane and rather accumulate on it. In contrast, they do not affect assembly and transport of immature virus particles. We determined the three-dimensional structures of unmyristoylated species of both mutants using isotopically aided NMR spectroscopy. Comparison of their structures with the structure of the wild type MA shows that the mutation caused only marginal changes of the structural motif. In both cases it increased the size and hydrophobicity of the protein interior. Isoleucines 41 and 78 in T41I/T78I and phenylalanines 28 and 67 are oriented to the protein core in contrast to the original amino acid residues and they influence the interaction of the matrix protein interior with the myristic acid. This finding supports a hypothesis that the phenotypic change of the mutant is caused by an enhanced interaction of the myristic acid with more hydrophobic protein core, which prevents its exposure and finally abrogates the interaction of immature viral particles with the cytoplasmic membrane. To prove  the hypothesis we focus on the  determination of structure of myristoylated MA proteins with the emphasis to the interaction of the myristoyl with protein core.

 

This work was supported by the Czech Ministry of Education 1M6837805002, MSM 6046137305, and ME 904, Grant Agency of Czech Republic # 203/07/0872 and grant # CA 27834 from the National Institutes of Health.