Characterization of the binding of Fe(III) to F₁ATPase from bovine heart mitochondria

Fe(III) Binding to Bacillus PS3 F1ATPase, αβ Subcomplexes and Isolated α- and β-Subunits

“…Considering that isolated ␤-subunit binds iron both in "empty" and "closed" conformation induced by Mg 2ϩ -ADP, it is plausible to suppose that the region containing the Fe(III) site can be accessible in the closed conformation of free ␤ but not in the closed conformation of ␤ in TF 1 as a consequence of intersubunit contacts. This strongly suggests that the region may be that facing the ␣/␤ interface, in accordance with our previous proposal that the Fe(III) site is located near the nucleotide binding site (4).…”

“…Fe(III)-TF 1 and Fe(III)-MF 1 adducts show characteristic EPR signals at g ϭ 4.3, which have similar shapes (4,5). In MF 1 , EPR provides evidence for the location of the Fe(III) site near one of the six nucleotide binding sites.…”

“…In MF 1 , EPR provides evidence for the location of the Fe(III) site near one of the six nucleotide binding sites. This has been proposed on the basis of the changes of the EPR spectrum induced by phosphate binding to the two kinds of sites for this anion existing in the enzyme (4,13). Considering the high homology of the nucleotide-binding subunits in F 1 ATPase (14), it is possible to infer that also in TF 1 the Fe(III) site is located in one of the large subunits.…”

“…In fact, it has been described both in MF 1 (4) and in Thermophilic Bacillus PS3 F 1 ATPase (TF 1 ) (5). In both enzymes, Fe(III) binding to such site occurs irrespective of the filling of the proteins with Mg 2ϩ -free nucleotides and the site is named Fe(III) nucleotideindependent site.…”

Excessive ATP hydrolysis in ischemic myocardium by mitochondrial F1F0-ATPase: effect of selective pharmacological inhibition of mitochondrial ATPase hydrolase activity

“…This small 80-amino acid protein specifically inhibits the ATP hydrolase activity of F 1 F 0 -ATPase (5,20,26). The binding of IF 1 to F 1 F 0 -ATPase is optimal at pH 6.7 and requires the hydrolysis of ATP in the absence of an electrochemical gradient, conditions also seen during myocardial ischemia (13,19). The inhibition of the ATP hydrolase activity by IF 1 is reversible upon restoration of the mitochondrial electrochemical gradient and increased pH as might be seen during reperfusion (30).…”