Mitochondrial selenium-75 uptake and regulation revealed by kinetic analysis.
TL;DR: The study revealed thiol-selenite interactions of metabolic significance during selenite uptake in mitochondria of the larvae of the insectC.
Abstract: Uptake of Na2
75SeO3 by mitochondria of the larvae of the insectC. cephalonica reared at different dietary selenium (Se) levels revealed:
A differential affinity for Na2
75SeO3 was elicited in the mitochondrial protein fractions of different dietary Se groups and correlated well with the pattern and the ratio of distribution of incorporated75Se in protein to nonprotein fractions. Kinetic studies on75Se uptake by whole mitochondria negated passive diffusion of selenite and revealed a trend of negative cooperativity confirmed by Hill and Scatchard plots. Half saturation value was estimated to be approx 13 nmole Se/mg mitochondrial protein. Scatchard plot for75Se uptake was biphasic and the high affinity binding sites were estimated to be around 5 nmole/mg mitochondrial protein. Calculated dissociation constants revealed maximal affinity for75Se in the 1.5 ppm group (KSe 0.0034 nM) and minimal in the basal group (KSe 0.007 nM). In the mitochondria of all the three dietary Se groups, the estimated low affinity sites amounted to be 15–19 nmole/mg mitochondrial protein. Inherent Se in the mitochondria of the high Se group positively enhanced the incorporation of75Se in the mitochondrial protein fraction. About 20–30% of the total uptake was indicated to be energy linked as revealed by studies with respiratory inhibitors. Addition of sulfite and sulfate (5–25 μM) in the medium, inhibited75Se uptake by 35–55%, suggestive of the involvement of the dicarboxylate port. Thiol interactive75Se uptake was confirmed by the inhibition mediated by mersalyl and NEM up to 50–70%. The study revealed thiol-selenite interactions of metabolic significance during selenite uptake.
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TL;DR: Application of omics integration to model systems reveals a critical role for metal ion homeostasis broadly impacting mitochondrial reprogramming and shows that trans-omics associations are more robust and biologically relevant than single omics associations.
Abstract: Significance: Elucidation of the central importance of mitophagy in homeostasis of cells and organisms emphasizes that mitochondrial functions extend far beyond short-term needs for energy production. In mitochondria systems biology, the mitochondrial genome, proteome, and metabolome operate as a functional network in coordination of cell activities. Organization occurs through subnetworks that are interconnected by membrane potential, transport activities, allosteric and cooperative interactions, redox signaling mechanisms, rheostatic control by post-translational modifications, and metal ion homeostasis. These subnetworks enable use of varied energy precursors, defense against environmental stressors, and macromolecular rewiring to titrate energy production, biosynthesis, and detoxification according to cell-specific needs. Rewiring mechanisms, termed mitochondrial reprogramming, enhance fitness to respond to metabolic resources and challenges from the environment. Maladaptive responses can cause cell death. Maladaptive rewiring can cause disease. In cancer, adaptive rewiring can interfere with effective treatment. Recent Advances: Many recent advances have been facilitated by the development of new omics tools, which create opportunities to use data-driven analysis of omics data to address these complex adaptive and maladaptive mechanisms of mitochondrial reprogramming in human disease. Critical Issues: Application of omics integration to model systems reveals a critical role for metal ion homeostasis broadly impacting mitochondrial reprogramming. Importantly, data show that trans-omics associations are more robust and biologically relevant than single omics associations. Future Directions: Application of omics integration to mitophagy research creates new opportunities to link the complex, interactive functions of mitochondrial form and function in mitochondria systems biology.
17 citations
TL;DR: The present study confirms the controlled nature of 75Se uptake by plant mitochondria, with a cooperative effect during Se transport and the interaction of active thiols in the process.
Abstract: Uptake of (75Se) added in vitro was followed in mitochondria isolated from Trigonella foenum-graecum seedlings grown under different Se status (0.5–1.0 ppm) and with added mimosine (0.1 mM). Uptake of 75Se followed with added Na275SeO3 upto 20 µM in the medium was nonlinear in all the groups. Kinetic analyses of the uptake of 75Se for 1 min were carried out for all the groups. The results indicated a cooperative effect during Se transport. Graphical analyses using the Hill plot and Scatchard plot confirmed the existence of negative cooperativity during 75Se uptake. Scatchard plots were biphasic, suggesting the probable presence of two classes of binding sites. The presence of succinate or ATP in the incubation medium inhibited 75Se uptake by 40%. Studies with mitochondrial respiratory inhibitors indicated the uptake to be energy independent. A decrease in the uptake of 75Se by 40% effected by HgCl2, N-ethyl maleimide, and iodoacetate confirmed the interaction of active thiols in the process. The present study confirms the controlled nature of 75Se uptake by plant mitochondria.
5 citations
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Journal Article•
TL;DR: Procedures are described for measuring protein in solution or after precipitation with acids or other agents, and for the determination of as little as 0.2 gamma of protein.
289,852 citations
TL;DR: A water-soluble (at pH 8) aromatic disulfide [5,5′-dithiobis(2-nitrobenzoic acid] has been synthesized and shown to be useful for determination of sulfhydryl groups.
23,232 citations
TL;DR: This chapter discusses microsomal lipid peroxidation, a complex process known to occur in both plants and animals that involves the formation and propagation of lipid radicals, the uptake of oxygen, a rearrangement of the double bonds in unsaturated lipids, and the eventual destruction of membrane lipids.
Abstract: Publisher Summary This chapter discusses microsomal lipid peroxidation Lipid peroxidation is a complex process known to occur in both plants and animals It involves the formation and propagation of lipid radicals, the uptake of oxygen, a rearrangement of the double bonds in unsaturated lipids, and the eventual destruction of membrane lipids, producing a variety of breakdown products, including alcohols, ketones, aldehydes, and ethers Biological membranes are often rich in unsaturated fatty acids and bathed in an oxygen-rich, metal-containing fluid Lipid peroxidation begins with the abstraction of a hydrogen atom from an unsaturated fatty acid, resulting in the formation of a lipid radical The formation of lipid endoperoxides in unsaturated fatty acids containing at least 3 methylene interrupted double bonds can lead to the formation of malondialdehyde as a breakdown product Nonenzymic peroxidation of microsomal membranes also occurs and is probably mediated in part by endogenous hemoproteins and transition metals The direct measurement of lipid hydroperoxides has an advantage over the thiobarbituric acid assay in that it permits a more accurate comparison of lipid peroxide levels in dissimilar lipid membranes
11,945 citations
TL;DR: When hemolyzates from erythrocytes of selenium-deficient rats were incubated in vitro in the presence of ascorbate or H2O2, added glutathione failed to protect the hemoglobin from oxidative damage.
Abstract: When hemolyzates from erythrocytes of selenium-deficient rats were incubated in vitro in the presence of ascorbate or H(2)O(2), added glutathione failed to protect the hemoglobin from oxidative damage. This occurred because the erythrocytes were practically devoid of glutathione-peroxidase activity. Extensively purified preparations of glutathione peroxidase contained a large part of the (75)Se of erythrocytes labeled in vivo. Many of the nutritional effects of selenium can be explained by its role in glutathione peroxidase.
6,893 citations
01 Jan 1956
TL;DR: How the respiratory chain and oxidative phosphorylation works and which substances may disable it are explained.
Abstract: The respiratory chain and oxidative phosphorylation are of utter importance for a cell’s metabolism. Here, the energy won from ingested food is being converted into our body’s energy unit (adenosine triphosphate). As the name respiratory chain suggests, oxygen also plays an important role. The following article will explain how exactly this complex mechanism works and which substances may disable it.
1,678 citations