Figure 4. BART product inhibition is relieved by ARL3 effectors which mediate its turnover.
(A) Nucleotide exchange of ARL3 was assayed in a multiple turnover experiment with a limiting addition of BART. Fluorescence polarisation was measured following nucleotide addition for a mixture of 20 μM ARL3mantGDP, 20 μM ARL13B, and 1 μM BART in the presence of either 150 μM GppNHp (red) or 150 μM GDP (blue). (B) Fluorescence polarisation was measured for a mixture of 5 μM ARL3mantGDP, 100 μM GppNHp, and 1 μM ARL13B18-278 (grey). The measurements were repeated in the presence of 5 μM UNC119A (yellow), 2 μM BART (blue), or a mixture of UNC119A and BART at the aforementioned concentrations (orange). All reactions were initiated by the addition of GppNHp. (C) SPR sensorgrams of ARL3GppNHp (640 nM) bound to immobilised GST-BART undergoing nine washing steps (black arrows) with either running buffer (red), or with 2 μM PDEδ (blue). The data was fitted to a single exponential equation using GraFit, and the fitted curves are shown on the right, along with the corresponding rate constants.