Assembly of MHC class I peptide complexes from the perspective of disulfide bond formation

Assembly of functional major histocompatibility complex (MHC) class I peptide complexes within the endoplasmic reticulum is critically important for the development of an adaptive immune response. The highly regulated loading of peptides onto MHC class I molecules is controlled by a multi-component chaperone system called the MHC class I peptide loading complex. The recent identification of the thioredoxin family member ERp57 as a component of the loading complex led to an interesting question: Why is there a thiol-disulfide oxidoreductase inside a complex dedicated to inserting peptides into a receptor binding site? Most recently, specific ERp57-mediated disulfide bond rearrangements have been identified inside the loading complex. What these biochemical events mean for the peptide loading process remains a matter of conjecture. While several important questions wait to be answered, this review intends to summarize our current view of the oxidative folding of MHC class I molecules and addresses the question of how the receptor ligand interaction might be regulated by thiol-based redox reactions.     

Structure/function analysis of a critical disulfide bond in the active site of l-xylulose reductase

l-Xylulose reductase (XR) is involved in water re-absorption and cellular osmoregulation. The crystal structure of human XR complemented with site-directed mutagenesis (Cys138Ala) indicated that the disulfide bond in the active site between Cys138 and Cys150 is unstable and may affect the reactivity of the enzyme. The effects of reducing agents on the activities of the wild-type and mutant enzymes indicated the reversibility of disulfide-bond formation, which resulted in three-fold decrease in catalytic efficiency. Furthermore, the addition of cysteine (>2 mM) inactivated human XR and was accompanied by a 10-fold decrease in catalytic efficiency. TOF-MS analysis of the inactivated enzyme showed the S-cysteinylation of Cys138 in the wild-type and Cys150 in the mutant enzymes. Thus, the action of human XR may be regulated by cellular redox conditions through reversible disulfide-bond formation and by S-cysteinylation. Received 25 January 2009; received after revision 12 February 2009; accepted 16 February 2009 H.-T. Zhao, S. Endo: These two authors contribute equally to this work.     

Synthesis of Eel-Calcitonin and [Asu1,7]-Eel-Calcitonin: Contribution of the disulfide bond to the hormonal activity

Summary Eel-calcitonin and its [Asu^1,7]-analog, deamino-dicarba-analog, were synthesized by the conventional solution method. The natural-type product showed 4300 MRC U/mg in the hypocalcemic potency which was comparable to that of the natural hormone isolated from eel. Hormonal activity of the Asu-analog was also as high as 3400 MRC U/mg.     

Differential effect of oxidized glutathione or acetylphenylhydrazine on individual electrophoretic components of red cell acid phosphatases

Riassunto Le frazioni che costituiscono il normale quadro elettroforetico delle fosfatasi acide eritrocitarie mostrano una differente resistenza al trattamento con glutatione ossidato o con acetilfenilidrazina: le frazioni lente dei genotipi studiati sono apparse infatti più stabili.     

Time course study of the changes in blood glutathione induced by acute ethanol intoxication in the rat

Acute ethanol treatment of rats (5 g/kg) has a biphasic effect on the glutathione content of the erythrocyte. After 3 h of intoxication there is a diminution in total GSH equivalents, followed by a recovery to basal values 6 h after treatment. The decrease of total GSH equivalents is mainly due to a diminution of the oxidized form of the tripeptide. Concomitantly a marked increase in the plasma level of glutathione was found at 3 h, followed by a diminution to values obtained at time zero.     

Nonspecific reaction of a thiol:Protein disulfide oxidoreductase with the disulfide bonds of insulin

Summary A thiol:protein disulfide oxidoreductase from bovine liver was isolated after separation from protein disulfide isomerase. The enzyme, after activation (reduction) with glutathione, was reacted with stoichiometric amounts of insulin and the sulfhydryl groups of the partially reduced hormone were labeled with iodo (l-¹⁴C)acetamide. After separation of the insulin chains, the radioactivity was found in both the peptides, with a ratio A-chain/B-chain equal to 2/1.     

Nonspecific reaction of a thiol: protein disulfide oxidoreductase with the disulfide bonds of insulin

A thiol: protein disulfide oxidoreductase from bovine liver was isolated after separation from protein disulfide isomerase. The enzyme, after activation (reduction) with glutathione, was reacted with stoichiometric amounts of insulin and the sulfhydryl groups of the partially reduced hormone were labeled with iodo (l-14C)acetamide. After separation of the insulin chains, the radioactivity was found in both the peptides, with a ratio A-chain/B-chain equal to 2/1.     

The effects of vitamin A nutritional status on glutathione,glutathione transferase and glutathione peroxidase activities in rat intestine

Summary In rat intestine, the glutathione level was increased, glutathione peroxidase activity decreased and glutathione-S-transferase unchanged by vitamin A deficiency.     

The effects of vitamin A nutritional status on glutathione, glutathione transferase and glutathione peroxidase activities in rat intestine

In rat intestine, the glutathione level was increased, glutathione peroxidase activity decreased and glutathione-S-transferase unchanged by vitamin A deficiency.     

The redox cleavage of the sulfur-sulfur bond and carbon-sulfur bond in organic disulfides by a model coenzyme

Résumé Le N-Benzyl-1,4-dihydronicotinamide réduit, par un mécanisme redox de transfert d'un électron, laliaison disulfide de plusieurs disulfides organiques tels que le diphényl disulfide, l'-lipoamide et le tétraméthylthiuram disulfide. Les réactions chimiques sont comparées à l'oxydation enzymique de la nicotinamide-adénine nucléotide.     

Unusual lability of the amide bond in N-methylhippuric acid

Zusammenfassung Bei 100° und pH 2,2 bis 3,5 wird die Amidbindung der N-Methylhippursäure weitgehend hydrolytisch gespalten, während Hippursäure unter denselben Bedingungen stabil ist.     

The glutathione status of the rat liver

Summary For the determination of cellular total glutathione, a new method is presented based on a fluorometric procedure. The relation between reduced glutathione, mixed glutathione disulfides and disulfide glutathione will be designated the glutathione status.Supported by DFG (Ha 743/3).     

On the stability of the guanine-cytosine hydrogen bond

Zusammenfassung Die Änderung des molaren Extinktionskoeffizienten natürlicher Desoxyribonucleinsäuren wurde untersucht in Abhängigkeit der Basenzusammensetzung. Aus den experimentellen Befunden wird geschlossen, dass die Wasserstoffbindung zwischen Cytosin und Guanin im Doppelhelix schwach ist und in wässriger Lösung ohne die stabilisierende Wirkung benachbarter Adenin-Tyminbindungen nicht vorliegt. Die mit der Nucleinsäure verbundenen Proteine liefern einen zusätzlichen Stabilisationsfaktor zur Guanin- und Cytosinbindung.     

Hydrogen bonding by the sulphydryl group of glutathione

Summary The occurrence of hydrogen bond in the sulphydryl group of glutathione was investigated by means of Raman Spectroscopy. Evidence is obtained that SH group is free and H-bonding does not occur.     

The glutathione status of the rat liver.

For the determination of cellular total glutathione, a new method is presented based on a fluorometric procedure. The relation between reduced glutathione, mixed glutathione disulfides and disulfide glutathione will be designated the glutathione status.     

Changes in the cardiac glutathione status after ischemia and reperfusion

Summary In the isolated and perfused rabbit heart ischemia induced a rapid decline of contractility, associated with a reduction of the content of tissue GSH with no significant changes in GSSG. Reperfusion induced a small recovery of contractility, a substantial release of total glutathione and a further decrease in the content of tissue GSH with a significant increase of tissue GSSG. Glutathione reductase and glutathione peroxidase activities were not affected by ischemia and reperfusion. This study suggests a possible role for glutathione in the determination of functional damage induced by myocardial ischemia and reperfusion.This study was supported by a grant from Ministero Pubblica Istruzione and CNR Rome (no 8202331.56).     

Changes in the cardiac glutathione status after ischemia and reperfusion

In the isolated and perfused rabbit heart ischemia induced a rapid decline of contractility, associated with a reduction of the content of tissue GSH with no significant changes in GSSG. Reperfusion induced a small recovery of contractility, a substantial release of total glutathione and a further decrease in the content of tissue GSH with a significant increase of tissue GSSG. Glutathione reductase and glutathione peroxidase activities were not affected by ischemia and reperfusion. This study suggests a possible role for glutathione in the determination of functional damage induced by myocardial ischemia and reperfusion.     

Influence of glutathione on serum cholesterol in rabbits

Zusammenfassung In Kaninchen erfolgt auf intramuskuläre Injektionen von 0.1 g reduziertem Glutathion nach 24 h ein hoch signifikanter Anstieg des Serumcholesterins. Kleinere Dosen, oder orale Verabreichung von 0.1 g, haben keine derartige Wirkung.Oxydiertes Glutathion,dl-Cystein und Glykokoll zeigen bei Kaninchen keinen eindeutigen und unmittelbaren Einfluss auf Serumcholesterin.

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This investigation was supported by a research grant H-4568 from the National Heart Institute, Public Health Service (U.S.A.).     

Hydrogen bonding by the sulphydryl group of glutathione.

The occurrence of hydrogen bond in the sulphydryl group of glutathione was investigated by means of Raman Spectroscopy. Evidence is obtained that SH group is free and H-bonding does not occur.