The surface behavior of the HIV-GAG MA domain and its N-terminal peptides is finely-tuned by protein myristoylation and nucleic acid binding

PÉREZ SOCAS, LUIS BENITO; AMBROGGIO ERNESTO ESTEBAN

Tucuman

Congreso; III Latin American Federation of Biophysical Societies (LAFeBS) ? IX IberoAmerican Congress of Biophysics ? XLV Reunion Anual SAB 2016 / Sica, Mauricio P, 1a ed. ? San Carlos de Bariloche: Sociedad Argentina de Biofísica, 2016; 2016

Sociedad Argentina de Biofísica

Within the lifecycle of HIV, the capsid protein GAG has a fundamentalrole in coordinating the assembly process of the virus at the plasmaticmembrane. The interaction of this protein with the lipid bilayeris mediated by its N-terminal myristoylated MA domain. In addition,MA possess a highly basic region (HBR) responsible for the interactionwith the negative lipids of the plasmatic membrane, especiallywith PIP2. It is known that this domain also interacts with the viralgenome, in what could be a regulatory step of the assembly process.Here we show the modulation of the surface properties of theMA domain and N-terminal peptides (GAGnt) provoked by the presenceof DNA. We performed protein Langmuir monolayer experimentsusing the recombinant MA protein and synthetic GAGnt peptides, inboth myristoilated and unmyristoilated variants, and in the presenceor absence of the DNA sequence Sel25, which is known to interactwith MA domain with nanomolar affinity. Furthermore, we carriedout Brewster angle microscopy (BAM) experiments to visualize the effectsof the oligonucleotide on the monolayer lateral structure. Experimentsfrom pure-peptide monolayers show clear-cut differences whenthe peptide was myristoylated and in the presence of DNA respect tothe un-myristoylated peptide mononayer. Notable variations on the filmstability was observed, with a noticeable higher collapse pressure formyrGAGnt monolayers than for GAGnt films. This parameter is alsoaffected by the presence of DNA, being the case of myrGAGnt themost drastic change, in which the isotherm almost vanishes when Sel25is present. On the other hand, MA and myrMA proteins show slightdifferences on the surface biophysical properties. Lateral-compressionisotherms from pure protein monolayer are apparently not affected bythe presence of DNA. However, for the case of myrMA it is remarkablethe presence of laterally-separated structural domains, observed withBAM, wich disappear in the presence of DNA.