Abstract
The F1F0-ATP synthase translates a proton flux across the inner mitochondrial membrane into a mechanical rotation, driving anhydride bond formation in the catalytic portion. The complex’s membrane-embedded motor forms a proteinaceous channel at the interface between Atp9 ring and Atp6. To prevent unrestricted proton flow dissipating the H+-gradient, channel formation is a critical and tightly controlled step during ATP synthase assembly. Here we show that the INA complex (INAC) acts at this decisive step promoting Atp9-ring association with Atp6. INAC binds to newly synthesized mitochondrial-encoded Atp6 and Atp8 in complex with maturation factors. INAC association is retained until the F1-portion is built on Atp6/8 and loss of INAC causes accumulation of the free F1. An independent complex is formed between INAC and the Atp9 ring. We conclude that INAC maintains assembly intermediates of the F1 F0-ATP synthase in a primed state for the terminal assembly step–motor module formation.
Highlights
The F1F0-ATP synthase translates a proton flux across the inner mitochondrial membrane into a mechanical rotation, driving anhydride bond formation in the catalytic portion
We have found that a lack of the INA complex affects the biogenesis of the F1F0-ATP synthase leading to the accumulation of unassembled, free F1-subcomplexes
Our analyses show that the last F1F0-ATP synthase assembly step, the connection of Atp6/Atp8-containing assembly intermediates with the Atp[9] ring, is impaired by a lack of INA complex (INAC)
Summary
The F1F0-ATP synthase translates a proton flux across the inner mitochondrial membrane into a mechanical rotation, driving anhydride bond formation in the catalytic portion. An independent complex is formed between INAC and the Atp[9] ring. The F1F0-ATP synthase utilizes the proton gradient across the mitochondrial inner membrane, generated by the respiratory chain, to drive. Protons translocate from the intermembrane space across the inner membrane into the matrix through a channel that is formed by Atp[6] (subunit a in E. coli) and a ring of Atp[9] subunits (subunit c in E. coli). Coli) and a ring of Atp[9] subunits (subunit c in E. coli) This process converts the electrochemical gradient into a mechanical force eventually catalyzing formation of the anhydride bond in ATP1–3. S. cerevisiae enzyme can be divided into two major parts: (i) the matrix-exposed soluble F1, which is composed of the catalytic head and a central stalk that translates motor rotation to the catalytic centers; (ii) the membrane-bound F0, which contains the peripheral stalk and the membrane-embedded rotor segment
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