Divalent Metal Ions in Plant Mitochondria and Their role in Interactions with Proteins and Oxidative Stress-Induced Damage to Respiratory Function

Understanding the metal ion content of plant mitochondria and metal ion interactions with the proteome are vital for insightsinto both normal respiratory function and the process of protein damage during oxidative stress. We have analyzed the metalcontent of isolated Arabidopsis (Arabidopsis thaliana) mitochondria, revealing a 26:8:6:1 molar ratio for iron:zinc:copper:manganese and trace amounts of cobalt and molybdenum. We show that selective changes occur in mitochondrial copper andiron content following in vivo and in vitro oxidative stresses. Immobilized metal affinity chromatography charged with Cu2+,Zn2+, and Co2+ was used to identify over 100 mitochondrial proteins with metal-binding properties. There were strongcorrelations between the sets of immobilized metal affinity chromatography-interacting proteins, proteins predicted to containmetal-binding motifs, and protein sets known to be oxidized or degraded during abiotic stress. Mitochondrial respiratorychain pathways and matrix enzymes varied widely in their susceptibility to metal-induced loss of function, showing theselectivity of the process. A detailed study of oxidized residues and predicted metal interaction sites in the tricarboxylic acidcycle enzyme aconitase identified selective oxidation of residues in the active site and showed an approach for broaderscreening of functionally significant oxidation events in the mitochondrial proteome.