scholarly journals Structural changes in mitochondria induced by uncoupling reagents. The response to proteolytic enzymes

1968 ◽  
Vol 106 (3) ◽  
pp. 711-717 ◽  
Author(s):  
Eugene C. Weinbach ◽  
Joel Garbus
Keyword(s):  
Structural Changes ◽  
Proteolytic Enzymes ◽  
Free Acid ◽  
Liver Mitochondria ◽  
Mitochondrial Proteins ◽  
Rat Liver Mitochondria ◽  
Phospholipid Complex ◽  
Structural Alterations ◽  
Uncoupling Of Oxidative Phosphorylation ◽  
Contrast Interaction

Interaction of uncoupling reagents with bovine serum albumin markedly inhibited its hydrolysis by proteolytic enzymes. The inhibition presumably is due to conformational transitions in the protein substrate induced by the binding of the ligand–uncoupling reagents. The proteolysis of casein, a protein that does not bind these reagents, was not affected, indicating that the proteinases themselves were not inactivated. In contrast, interaction of uncoupling reagents with freshly isolated rat liver mitochondria enhanced their susceptibility to proteolytic enzymes. This was shown by an increase in the release of ninhydrin-reacting material, by an increase in free acid groups and by a decrease in the turbidity of the mitochondrial suspensions. These effects, although opposite in direction to those obtained with albumin, are also presumed to indicate structural changes in the mitochondrial proteins and a disorganization of the protein–phospholipid complex. It is suggested that such structural alterations are expressed functionally as the uncoupling of oxidative phosphorylation.

STRUCTURAL CHANGES ASSOCIATED WITH THE RELEASE OF ENZYMES FROM RAT-LIVER MITOCHONDRIA BY FREEZING

1966 ◽  
Vol 44 (6) ◽  
pp. 775-781 ◽  
Author(s):  
C. V. Lusena ◽  
C. M. S. Dass
Keyword(s):  
Rat Liver ◽  
Structural Modification ◽  
Structural Changes ◽  
Sodium Deoxycholate ◽  
Liver Mitochondria ◽  
Maximum Activity ◽  
Supernatant Fraction ◽  
Rat Liver Mitochondria ◽  
Mitochondrial Disruption ◽  
Partial Release

Suspensions of rat-liver mitochondria in 0.44 M sucrose, after they were frozen and thawed under defined conditions, were partitioned into three sedimentable and one supernatant fraction by differential centrifugation. These were analyzed for optical density, protein content, and for activities of glutamate dehydrogenase (GD) and 3-hydroxybutyrate dehydrogenase (BD) with exogenous nicotinamide–adenine dinucleotide (NAD) both as maximum activity after sodium deoxycholate treatment and as activity released by freezing. Pellets of the three sedimentable fractions were also examined in the electron microscope. When dehydrogenases were not released by a freezing treatment, no structural changes were detected. Release of BD, which was accompanied by release of GD as well, was associated with mitochondrial disruption and drastic rearrangement of mitochondrial membranes. On the other hand, release of GD without BD occurred from swollen and emptied mitochondria. The partial release of enzymes in a preparation was not associated with a partial structural modification of all of the mitochondria, but rather with drastic structural changes in only some of them.

scholarly journals DB75, a Novel Trypanocidal Agent, Disrupts Mitochondrial Function in Saccharomyces cerevisiae

2004 ◽  
Vol 48 (10) ◽  
pp. 3968-3974 ◽  
Author(s):  
Charlotte A. Lanteri ◽  
Bernard L. Trumpower ◽  
Richard R. Tidwell ◽  
Steven R. Meshnick
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mitochondrial Function ◽  
Early Stage ◽  
Model Organism ◽  
Liver Mitochondria ◽  
Yeast Cells ◽  
Rat Liver Mitochondria ◽  
Pneumocystis Jiroveci ◽  
Cellular Target ◽  
Uncoupling Of Oxidative Phosphorylation

ABSTRACT The aromatic diamidines represent a class of compounds with broad-spectrum antimicrobial activity; however, their development is hindered by a lack of understanding of their mechanism of antimicrobial action. DB75 [2,5-bis(4-amidinophenyl)furan] is a trypanocidal aromatic diamidine that was originally developed as a structural analogue of the antitrypanosomal agent pentamidine. DB289, a novel orally active prodrug of DB75, is undergoing phase IIb clinical trials for early-stage human African trypanosomiasis, Pneumocystis jiroveci carinii pneumonia, and malaria. The purpose of this study was to investigate mechanisms of action of DB75 using Saccharomyces cerevisiae as a model organism. The results of this investigation suggest that DB75 inhibits mitochondrial function. Yeast cells relying upon mitochondrial metabolism for energy production are especially sensitive to DB75. DB75 localizes (by fluorescence) within the mitochondria of living yeast cells and collapses the mitochondrial membrane potential in isolated yeast mitochondria. Furthermore, addition of DB75 to yeast cells or isolated rat liver mitochondria results in immediate uncoupling of oxidative phosphorylation and subsequent inhibition of respiration. We conclude that the mitochondrion is a cellular target of DB75 in yeast cells and anticipate that the results of this study will aid in the target-based design of new antimicrobial aromatic diamidines.

The Effect of Insulin on Mitochondrial Particles

1967 ◽  
Vol 25 ◽  
pp. 160-161 ◽  
Author(s):  
Burton B. Silver ◽  
James C. Hall
Keyword(s):  
Bovine Serum Albumin ◽  
Structural Changes ◽  
Normal Values ◽  
Liver Mitochondria ◽  
Synergistic Action ◽  
Diabetic Rat ◽  
Rat Liver Mitochondria ◽  
Structural Studies

Correlative biochemical and structural studies have shown that insulin and Mg++ may act to alter the configuration and also enhance the efficiency of coupled phosphorylation in sonicated fragments of diabetic rat liver mitochondria. The diabetic preparations had consistently lowered P:O ratios which returned to normal values with addition of insulin in vivo or in vitro. Optimum coupling and structural changes with insulin required a Mg++ concentration of 5 × 10−5 M. Insulin remained effective diluted to a concentration of 2 × 10−4 I.U. per ml. Glutathione, bovine serum albumin, and Zn++ were ineffective in producing either coupling or structural changes. There seems to be a synergistic action of insulin and Mg++ in restoring P:O ratios in diabetic particles while simultaneously altering the structure toward normal control appearances. Fragments negatively stained with phosphotungstate indicated that the normal particles had well defined cristae with numerous evenly distributed, stalked subunits, 90 Å in diameter.

scholarly journals Spectrophotometric studies of acyl-coenzyme A synthetases of rat liver mitochondria

1970 ◽  
Vol 119 (3) ◽  
pp. 553-564 ◽  
Author(s):  
P. B. Garland ◽  
D. W. Yates ◽  
B. A. Haddock
Keyword(s):  
Rat Liver ◽  
Citrate Synthase ◽  
Free Acid ◽  
Spectral Characteristics ◽  
Difference Spectrum ◽  
Liver Mitochondria ◽  
The Other ◽  
Rat Liver Mitochondria ◽  
Synthetase Activity ◽  
Specific Enzyme

1. Deca-2,4,6,8-tetraenoic acid is a substrate for both ATP-specific (EC 6.2.1.2 or 3) and GTP-specific (EC 6.2.1.–) acyl-CoA synthetases of rat liver mitochondria. The enzymic synthesis of decatetraenoyl-CoA results in new spectral characteristics. The difference spectrum for the acyl-CoA minus free acid has a maximum at 376nm with εmM 34. Isosbestic points are at 345nm and 440nm. 2. The acylation of CoA by decatetraenoate in mitochondrial suspensions can be continuously measured with a dual-wavelength spectrophotometer. 3. By using this technique, three distinct types of acyl-CoA synthetase activity were demonstrated in rat liver mitochondria. One of these utilized added CoA and ATP, required added Mg2+ and corresponded to a previously described `external' acyl-CoA synthetase. The other two acyl-CoA synthetase activities utilized intramitochondrial CoA and did not require added Mg2+. Of these two `internal' acyl-CoA synthetases, one was insensitive to uncoupling agents, was inhibited by phosphate or arsenate, and corresponded to the GTP-specific enzyme. The other corresponded to the ATP-specific enzyme. 4. Atractylate inhibited the activity of the two internal acyl-CoA synthetases only when the energy source was added ATP. 5. The amount of intramitochondrial CoA acylated by decatetraenoate was independent of whether the internal ATP-specific or GTP-specific acyl-CoA synthetase was active. It is concluded that these two internal acyl-CoA synthetases have access to the same intramitochondrial pool of CoA. 6. The amount of intramitochondrial CoA that could be acylated with decatetraenoate was decreased by the addition of palmitoyl-dl-carnitine, 2-oxoglutarate, or pyruvate. These observations indicated that pyruvate dehydrogenase (EC 1.2.4.1), oxoglutarate dehydrogenase (EC 1.2.4.2), carnitine palmitoyltransferase (EC 2.3.1.–), citrate synthase (EC 4.1.3.7), and succinyl-CoA synthetase (EC 6.2.1.4) all have access to the same intramitochondrial pool of CoA as do the two internal acyl-CoA synthetases.

scholarly journals Proteolytic enzymes of rat liver mitochondria. Evidence for a mast cell origin

FEBS Letters ◽  
1979 ◽  
Vol 103 (1) ◽  
pp. 168-171 ◽  
Author(s):  
Rainer Haas ◽  
Peter C. Heinrich ◽  
Dieter Sasse
Keyword(s):  
Mast Cell ◽  
Rat Liver ◽  
Proteolytic Enzymes ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria

scholarly journals THE RATIO OF UBIQUINON REDOX FORMS IN THE RAT LIVER MITOCHONDRIA UNDER CONDITIONS OF DIFFERENT NUTRIENT SUPPLY

2020 ◽  
Vol 66 (6) ◽  
pp. 82-87
Author(s):  
O.M. Voloshchuk ◽  
◽  
G. P. Kopylchuk ◽  
М.S. Ursatyу ◽  
◽  
...  
Keyword(s):  
Free Radical ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Oxidative Modification ◽  
Mitochondrial Proteins ◽  
Rat Liver Mitochondria ◽  
Carbonyl Derivatives ◽  
High Sucrose Diet ◽  
Redox Forms ◽  
High Sucrose

The relationship between the quantitative ratio of redox forms of ubiquinone and the degree of free radical damage to mitochondrial proteins in rat liver against the background of nutritional imbalance was investigated. The animals were divided into the following experimental groups: I – animals receiving full-value semi-synthetic ration (control group); II – animals receiving high-sucrose diet; III – animals receiving low-protein high-sucrose diet. The content of total and oxidized ubiquinone was determined spectrophotometrically at 275 nm, the content of reduced ubiquinone was determined by the difference between the content of total and oxidized ubiquinone. The intensity of the oxidative modification of proteins was assessed by the accumulation of carbonyl derivatives in the reaction with 2,4-dinitrophenylhydrazine (2,4-DNPH), the content of free SH-groups was assessed by using the Elman reagent. It was found that the most pronounced decrease in the content of total ubiquinone (almost twice) and the redistribution of its redox forms (reduction of the content of reduced ubiquinone by 7.2 times against the background of an increase in the level of oxidized ubiquinone by 2 times) in rat liver mitochondria is observed in animals that received a diet high in sucrose against the background of alimentary protein deprivation. In addition, the animals of this group showed the most pronounced free radical oxidation of mitochondrial proteins, as evidenced by a 3.5-fold increase in the content of carbonyl derivatives and a 2.6-fold decrease in the content of free protein SH- groups. It was shown that nutritional protein deficiency is a critical factor affecting the intensity of free radical processes in mitochondria. The established changes in the ratio of the redox forms of ubiquinone and the degree of oxidative modification of mitochondrial proteins in rat liver could be considered as prerequisites for deepening the energy imbalance and violation of the functional activity of mitochondria under conditions of nutritional imbalance.

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