Effects of Fe(III) binding to the nucleotide-independent site of F-1-ATPase: enzyme thermostability and response to activating anions

Mitochondrial FI-ATPase was induced in different conformations by binding o f specific ligands, such as nucleotides. Then, Fourier transform infrared s pectroscopy (FT-IR) and kinetic analyses were run to evaluate the structura l and functional effects of Fe(Ill) binding to tile nucleotide-independent site. Binding of one equivalent of Fe(III) induced a localised stabilising effect on the FI-ATPase structure destabilised by a high concentration of N aCl, through rearrangements of the ionic network essential for the maintena nce of enzyme tertiary and/or quaternary structure. Concomitantly, a lower response of ATPase activity to activating anions was observed. Both FTIR an d kinetic data were in accordance with the hypothesis of the Fe(III) site l ocation near one of the catalytic sites, i.e. at the alpha/beta subunit int erface. (C) 2001 Published by Elsevier Science B.V. on behalf of the Federa tion of European Biochemical Societies.