ABCG2 ATPase Assay

The ATP hydrolysis activity of ABCG2 ATPase was evaluated using PREDEASY ATPase Kits (TEBU-BIO nv, Boechout, Belgium) with modified protocols (Wu et al., 2019). Membrane vesicles were incubated in assay buffer, followed by the addition of MLN7243. The reaction was initiate by adding 5 mM ATP solution and terminated by adding SDS solution. The ATPase activity was measured by colorimetric method and calculated using the difference of the produced Pi with and without Na₃VO₄, which inhibits plasma membrane ATPases including Na⁺/K⁺-ATPase (Chifflet et al., 1988).