{"title":"Mapping of oxidative modifications on the alpha-keto glutarate dehydrogenase complex induced by singlet oxygen: Effects on structure and activity","authors":"","doi":"10.1016/j.freeradbiomed.2024.09.024","DOIUrl":null,"url":null,"abstract":"<div><div>The large multi-subunit mitochondrial alpha-keto glutarate dehydrogenase (KGDH) complex plays a key, rate-determining, role in the tricarboxylic acid (Krebs) cycle, catalyzing the conversion of alpha-keto glutarate to succinyl-CoA. This complex is both a source and target of oxidants, but the sites of modification and association with structural changes and activity loss are poorly understood. We report here oxidative modifications induced by Rose Bengal (RB) in the presence of O<sub>2</sub>, a source of singlet oxygen (<sup>1</sup>O<sub>2</sub>). A rapid loss of activity was detected, with this being dependent on light exposure, illumination time, and the presence of RB and O<sub>2</sub>. Activity loss was enhanced by D<sub>2</sub>O (consistent with <sup>1</sup>O<sub>2</sub> involvement), but diminished by both pre- and (to a lesser extent) post-illumination addition of lipoic acid and lipoamide. Aggregates containing all three KGDH subunits were detected on photooxidation. LC-MS experiments provided evidence for oxidation at 45 sites, including specific Met, His, Trp, Tyr residues and the lipoyllysine active-site cofactor. Products include mono- and di-oxygenated species, and kynurenine from Trp. Mapping of the modifications to the 3-D structure showed that these are localized to both the inner channel and the external surface, consistent with reactions of free <sup>1</sup>O<sub>2</sub>, however the sites and extent of modification do not correlate with their solvent accessibility. These products are generated concurrently with loss of activity, indicative of strong links between these events. These data provide evidence for the impairment of KGDH activity by <sup>1</sup>O<sub>2</sub> via the oxidation of specific residues on the protein subunits of the complex.</div></div>","PeriodicalId":12407,"journal":{"name":"Free Radical Biology and Medicine","volume":null,"pages":null},"PeriodicalIF":7.1000,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Free Radical Biology and Medicine","FirstCategoryId":"3","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0891584924006713","RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"BIOCHEMISTRY & MOLECULAR BIOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
The large multi-subunit mitochondrial alpha-keto glutarate dehydrogenase (KGDH) complex plays a key, rate-determining, role in the tricarboxylic acid (Krebs) cycle, catalyzing the conversion of alpha-keto glutarate to succinyl-CoA. This complex is both a source and target of oxidants, but the sites of modification and association with structural changes and activity loss are poorly understood. We report here oxidative modifications induced by Rose Bengal (RB) in the presence of O2, a source of singlet oxygen (1O2). A rapid loss of activity was detected, with this being dependent on light exposure, illumination time, and the presence of RB and O2. Activity loss was enhanced by D2O (consistent with 1O2 involvement), but diminished by both pre- and (to a lesser extent) post-illumination addition of lipoic acid and lipoamide. Aggregates containing all three KGDH subunits were detected on photooxidation. LC-MS experiments provided evidence for oxidation at 45 sites, including specific Met, His, Trp, Tyr residues and the lipoyllysine active-site cofactor. Products include mono- and di-oxygenated species, and kynurenine from Trp. Mapping of the modifications to the 3-D structure showed that these are localized to both the inner channel and the external surface, consistent with reactions of free 1O2, however the sites and extent of modification do not correlate with their solvent accessibility. These products are generated concurrently with loss of activity, indicative of strong links between these events. These data provide evidence for the impairment of KGDH activity by 1O2 via the oxidation of specific residues on the protein subunits of the complex.
期刊介绍:
Free Radical Biology and Medicine is a leading journal in the field of redox biology, which is the study of the role of reactive oxygen species (ROS) and other oxidizing agents in biological systems. The journal serves as a premier forum for publishing innovative and groundbreaking research that explores the redox biology of health and disease, covering a wide range of topics and disciplines. Free Radical Biology and Medicine also commissions Special Issues that highlight recent advances in both basic and clinical research, with a particular emphasis on the mechanisms underlying altered metabolism and redox signaling. These Special Issues aim to provide a focused platform for the latest research in the field, fostering collaboration and knowledge exchange among researchers and clinicians.