Redox Regulation of Arabidopsis Mitochondrial Citrate Synthase

• Published in: Molecular plant Vol. 7; no. 1; pp. 156 - 169
• Main Authors: Schmidtmann, Elisabeth, König, Ann-Christine, Orwat, Anne, Leister, Dario, Hartl, Markus, Finkemeier, Iris
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 2014; Cell Press
• Subjects: Amino Acid Sequence; Arabidopsis; Arabidopsis - cytology; Arabidopsis - enzymology; Arabidopsis - metabolism; Bacteriology; Citrate (si)-Synthase - chemistry; Citrate (si)-Synthase - metabolism; citrate synthase; Conserved Sequence; Cysteine; cysteine residues; Disulfides - chemistry; Enzyme Activation - drug effects; Enzymes; Hydrogen Peroxide - pharmacology; Isoenzymes - chemistry; Isoenzymes - metabolism; mitochondria; Mitochondria - enzymology; Mitochondria - metabolism; Models, Molecular; Molecular Sequence Data; Mutation; Oxidation-Reduction; Protein Conformation; redox regulation; TCA cycle; TCA循环; thioredoxin; Thioredoxins - metabolism; 半胱氨酸残基; 拟南芥; 柠檬酸合成酶; 氧化还原; 硫氧还蛋白; 线粒体; 转录后调控; citrate synthase; redox regulation; thioredoxin; Arabidopsis; mitochondria; TCA cycle; cysteine residues
• ISSN: 1674-2052; 1752-9867
• DOI: 10.1093/mp/sst144

Citrate synthase has a key role in the tricarboxylic （TCA） cycle of mitochondria of all organisms, as it cata- lyzes the first committed step which is the fusion of a carbon-carbon bond between oxaloacetate and acetyl CoA. The regulation of TCA cycle function is especially important in plants, since mitochondrial activities have to be coordinated with photosynthesis. The posttranslational regulation of TCA cycle activity in plants is thus far almost entirely unexplored. Although several TCA cycle enzymes have been identified as thioredoxin targets in vitro, the existence of any thioredoxin-dependent regulation as known for the Calvin cycle, yet remains to be demonstrated. Here we have investigated the redox regulation of the Arabidopsis citrate synthase enzyme by site-directed mutagenesis of its six cysteine residues. Our results indicate that oxidation inhibits the enzyme activity by the formation of mixed disulfides, as the partially oxidized citrate synthase enzyme forms large redox-dependent aggregates. Furthermore, we were able to demonstrate that thioredoxin can cleave diverse intraas well as intermolecular disulfide bridges, which strongly enhances the activity of the enzyme. Activity measurements with the cysteine variants of the enzyme revealed important cysteine residues affecting total enzyme activity as well as the redox sensitivity of the enzyme.