Distinct Gag interaction properties of HIV-1 RNA 5′ leader conformers reveal a mechanism for dimeric genome selection

Gag binds to 5′L_P with higher affinity at high salt concentrations, and the complex is more stable. The interaction between Gag and 5′L_P or 5′L_T was measured by fluorescence anisotropy (FA) at 50 mM (A), 300 mM (B), or 500 mM (C) sodium chloride. Data representative of at least three independent trials are shown. (D) In the FA salt titration assay, preformed Gag–5′L_P or Gag–5′L_T complexes were titrated with increasing concentrations of sodium chloride. FA was measured and fitted to sigmoidal curves.