文摘
The effect of increased expression or reconstitution of the mitochondrial inhibitor protein (IF1)on the dimer/monomer ratio (D/M) of the rat liver and bovine heart F1F0-ATP synthase was studied. The2-fold increased expression of IF1 in AS-30D hepatoma mitochondria correlated with a 1.4-fold increasein the D/M ratio of the ATP synthase extracted with digitonin as determined by blue native electrophoresisand averaged densitometry analyses. Removal of IF1 from rat liver or bovine heart submitochondrialparticles increased the F1F0-ATPase activity and decreased the D/M ratio of the ATP synthase.Reconstitution of recombinant IF1 into submitochondrial particles devoid of IF1 inhibited the F1F0-ATPaseactivity by 90% and restored partially the D/M ratio of the whole F1F0 complex as revealed by bluenative electrophoresis and subsequent SDS-PAGE or glycerol density gradient centrifugation. Thus, theinhibitor protein promotes or stabilizes the dimeric form of the intact F1F0-ATP synthase. A possiblelocation of the IF1 protein in the dimeric structure of the rat liver F1F0 complex is proposed. Accordingto crystallographic and electron microscopy analyses, dimeric IF1 could bridge the F1-F1 part of the dimericF1F0-ATP sythase in the inner mitochondrial membrane.