Myristoylation and Oligonucleotide Interaction Modulate Peptide and Protein Surface Properties: The Case of the HIV-1...

Myristoylated proteins typically develop a tight association with membranes. One example is the matrix domain (MA) of the HIV-1 Gag protein. In addition, MA is able to bind the Sel25 RNA sequence, a ligand that can act as a competitor for the interaction with the membrane. These properties make HIV-1 MA an attractive molecule to understand how protein and peptide surface properties can be controlled by myristoylation and oligonucleotide interaction. In this line, we analyzed the stability, thermodynamics, and the topography of Langmuir monolayers composed of the myristoylated or unmyristoylated versions of MA in the presence or the absence of a single-strand DNA (ssDNASel25) analogue of the Sel25 RNA sequence. With a similar approach, we compared the MA surface properties with those obtained from monolayers of myristoylated and unmyristoylated MA-derived peptides (first 21 residues of the MA sequence). Our results show that the protein or peptide films are destabilized by the presence of ssDNASel25, inducing solubilization of the monolayer components into the bulk phase. In addition, the oligonucleotide affects the protein-protein or peptide-peptide lateral interactions, provoking interfacial topography changes of the monolayers, visualized by Brewster angle microscopy. Furthermore, we also show how the myristoyl group has major effects on the lateral stability and the elasticity of the monolayers. Altogether, here we propose a general model considering the effect of myristoylation and the interaction with oligonucleotides on the interfacial properties of MA and derived peptides. In this model, we introduce a new role of the core region of MA (sequence of MA after the 21st residue) that confers higher lateral interfacial stability to the protein.