Iron Binding and Oxidation Kinetics in Frataxin CyaY of Escherichia coli

摘要: Friedreich's ataxia is associated with a deficiency in frataxin, conserved mitochondrial protein of unknown function. Here, we investigate the iron binding and oxidation chemistry Escherichia coli frataxin (CyaY), homologue human aim better understanding functional properties this protein. Anaerobic isothermal titration calorimetry (ITC) demonstrates that at least two ferrous ions bind specifically but relatively weakly per CyaY monomer (K(d) approximately 4 microM). Such weak consistent hypothesis functions as an chaperone. The bound Fe(II) oxidized slowly by O(2). However, occurs rapidly completely H(2)O(2) through non-enzymatic process stoichiometry Fe(II)/H(2)O(2), indicating complete reduction to H(2)O. In accord stoichiometry, electron paramagnetic resonance (EPR) spin trapping experiments indicate catalyzed production hydroxyl radical from Fenton greatly attenuated presence CyaY. Fe(III) produced binds six Fe(III)/CyaY independently measured kinetic, UV-visible, fluorescence, analysis pH-stat titrations. many 25-26 Fe(III)/monomer can protein, exhibiting UV absorption similar those hydrolyzed polynuclear species. Analytical ultracentrifugation measurements tetramer formed when added anaerobically protein; multiple aggregates are upon Fe(II). observed may afford mitochondria protection against iron-induced oxidative damage.