Phosphorylation of β subunit in F1F0 ATP synthase is associated with increased iron uptake in iron-overloaded heart mitochondria

Abstract

F1F0 ATP synthase was prepared from iron-overloaded heart mitochondria to study the effect of iron on mitochondria. As F1F0 ATP synthase was able to transport iron, proteoliposomes containing F1F0 ATP synthase were prepared to compare iron uptake between control and iron-overloaded mitochondria. A threefold increase in Vmax (nmol/min/mg) (6.35 ± 0.17 vs. 2.08 ± 0.06) and an eightfold increase in Km (μM) (7.5 ± 0.7 vs. 0.85 ± 0.5) by F1F0 ATP synthase for iron uptake were observed in iron-overloaded mitochondria. Mitochondrial ATP synthase prepared from iron-overloaded heart has a canonical subunit composition in an altered stoichiometry compared to the control enzyme: the α, β, γ, OSCP, d, a, δ, and c subunits increased, but the b, e, A6L, and F6 subunits decreased significantly. In addition, the pattern of β subunit isomers with different pIs changed. These isomers appeared to be associated with augmented phosphorylation by excess iron. © 2013 Korean Society for Integrative Biology.