Fig. 6.

Effects of A3G oligomerization on saturated binding. a Average quantities of A3G binding due to fast initial binding (blue) and slow oligomerization (red) for WT A3G and the three mutants. Values are based on A _fast and A _slow obtained from fitting two state binding model. Binding amplitudes are normalized based on total binding by FW mutant at saturation. Error bars are SEM for at least three measurements. b Measured extension of ssDNA due to simultaneous binding of both 50 nM WT and FW A3G. The initial binding occurs at a faster rate than that due to either 50 nM WT or FW alone and results in an extension change in between that due to either WT or FW binding alone. Over time, the extension change decreases as more stably bound WT A3G replaces the more transient FW A3G. c Schematic showing how the formation of A3G oligomers with reduced mobility can prevent full saturated binding of ssDNA substrate. This effect is observed for both WT A3G and the CTD mutants. In contrast, for the NTD (FW) mutant, bound A3G remains in a monomer state for a significantly longer period of time and is able to saturate all binding sites through restricted diffusion before forming oligomers. This model is consistent with previous measurements showing altered sliding and jumping of FW mutant A3G as compared to WT²²