Reducing Agents and Light Break an S–S Bond Activating Rhodopsin in Vivo in Chlamydomonas

2000 ◽  
Vol 275 (2) ◽  
pp. 286-291 ◽  
Author(s):  
Jureepan Saranak ◽  
Kenneth W Foster
Keyword(s):  
Reducing Agents ◽  
Light Break

scholarly journals Reductive Mobilization of Iron from Intact Ferritin: Mechanisms and Physiological Implication

2018 ◽  
Vol 11 (4) ◽  
pp. 120 ◽  
Author(s):  
Fadi Bou-Abdallah ◽  
John Paliakkara ◽  
Galina Melman ◽  
Artem Melman
Keyword(s):  
Protein Structures ◽  
Reducing Agents ◽  
Iron Core ◽  
Ferrous Ions ◽  
Major Pathway ◽  
Iron Mobilization ◽  
Iron Mineral ◽  
Mineral Core

Ferritins are highly conserved supramolecular protein nanostructures composed of two different subunit types, H (heavy) and L (light). The two subunits co-assemble into a 24-subunit heteropolymer, with tissue specific distributions, to form shell-like protein structures within which thousands of iron atoms are stored as a soluble inorganic ferric iron core. In-vitro (or in cell free systems), the mechanisms of iron(II) oxidation and formation of the mineral core have been extensively investigated, although it is still unclear how iron is loaded into the protein in-vivo. In contrast, there is a wide spread belief that the major pathway of iron mobilization from ferritin involves a lysosomal proteolytic degradation of ferritin, and the dissolution of the iron mineral core. However, it is still unclear whether other auxiliary iron mobilization mechanisms, involving physiological reducing agents and/or cellular reductases, contribute to the release of iron from ferritin. In vitro iron mobilization from ferritin can be achieved using different reducing agents, capable of easily reducing the ferritin iron core, to produce soluble ferrous ions that are subsequently chelated by strong iron(II)-chelating agents. Here, we review our current understanding of iron mobilization from ferritin by various reducing agents, and report on recent results from our laboratory, in support of a mechanism that involves a one-electron transfer through the protein shell to the iron mineral core. The physiological significance of the iron reductive mobilization from ferritin by the non-enzymatic FMN/NAD(P)H system is also discussed.

scholarly journals Modification of Cysteine Residues In Vitro and In Vivo Affects the Immunogenicity and Antigenicity of Major Histocompatibility Complex Class I–restricted Viral Determinants

1999 ◽  
Vol 189 (11) ◽  
pp. 1757-1764 ◽  
Author(s):  
Weisan Chen ◽  
Jonathan W. Yewdell ◽  
Rodney L. Levine ◽  
Jack R. Bennink
Keyword(s):  
Influenza Virus ◽  
Posttranslational Modifications ◽  
Synthetic Peptides ◽  
Influenza Virus Infection ◽  
Lymphocytic Choriomeningitis ◽  
Reducing Agents ◽  
Cysteine Residues ◽  
T Cell Lines

In studying the subdominant status of two cysteine-containing influenza virus nuclear protein (NP) determinants (NP39–47 and NP218–226) restricted by H-2Kd, we found that the antigenicity of synthetic peptides was enhanced 10–100-fold by treatment with reducing agents, despite the fact that the affinity for Kd was not enhanced. Reducing agents also markedly enhanced the immunogenicity of cysteine-containing peptides, as measured by propagation of long-term T cell lines in vitro. Similar enhancing effects were obtained by substituting cysteine with alanine or serine in the synthetic peptides, demonstrating that sulfhydryl modification of cysteine is responsible for the impaired antigenicity and immunogenicity of NP39–47 and NP218–226. We found similar effects for two widely studied, cysteine-containing peptides from lymphocytic choriomeningitis virus. The major modifications of cysteine-containing synthetic peptides are cysteinylation and dimerization occurring through cysteine residues. We demonstrate that both of these modifications occur in cells synthesizing a cytosolic NP218–226 minigene product and, further, that T cells specific for cysteinylated NP218–226 are induced by influenza virus infection in mice, demonstrating that this modification occurs in vivo. These findings demonstrate that posttranslational modifications affect the immunogenicity and antigenicity of cysteine-containing viral peptides and that this must be considered in studying the status of such peptides in immunodominance hierarchies.

scholarly journals The oxygenation of [3-methyl-3H]desacetoxycephalosporin C [7β-(5-d-aminadipamido)-3-methylceph-3-em-4-carboxylic acid] to [3-hydroxymethyl-3H]desacetylcephalosporin C by 2-oxoglutarate-linked dioxygenases from Acremonium chrysogenum and Streptomyces clavuligerus

1978 ◽  
Vol 173 (3) ◽  
pp. 839-850 ◽  
Author(s):  
M K Turner ◽  
J E Farthing ◽  
S J Brewer
Keyword(s):  
Carboxylic Acid ◽  
Deae Cellulose ◽  
Streptomyces Clavuligerus ◽  
Reducing Agents ◽  
Side Chain ◽  
Acremonium Chrysogenum ◽  
Hydroxymethyl Group ◽  
Methyl Group ◽  
Full Activity

Cell-free extracts of Acremonium chrysogenum and Streptomyces clavuligerus oxidize the 3-methyl group of desacetoxycephalosporin C to a 3-hydroxymethyl group. The enzyme responsible for this reaction in these organisms was purified 20- and 30-fold respectively by chromatography on DEAE-cellulose. The enzymes, which were assayed with [3-methyl-3H]desacetoxycephalosporin C as substrate, have the properties expected of 2-oxoglutarate-linked dioxygenases. They require 2-oxoglutarate, Fe2+ cations and a mixture of reducing agents (dithiothreitol and ascorbate) for full activity. The enzyme from A. chrysogenum, but not that S. clavuligerus, is activated about 10-fold when it is preincubated with a reaction mixture from which either desacetoxycephalosporin C or 2-oxoglutarate is omitted. Fe2+ cations seem to play a key role in this activation. Both enzymes seem highly specific for cephalosporins with the natural 7beta-(5-D-aminoadipamido) side chain and are likely to be responsible for the oxidation of the 3-methylcephem nucleus in vivo.

The Efficacy of Reducing Agents or Antioxidants in Blocking the Formation of Dense Cells and Irreversibly Sickled Cells In Vitro

Blood ◽  
1998 ◽  
Vol 91 (11) ◽  
pp. 4373-4378 ◽  
Author(s):  
Xunda A. Gibson ◽  
Archil Shartava ◽  
Jonah McIntyre ◽  
Carlos A. Monteiro ◽  
Yalin Zhang ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Reduced Glutathione ◽  
Cell Formation ◽  
Reducing Agents ◽  
Cellular Dehydration ◽  
Dense Cell ◽  
Human Use

Abstract We show that N-acetylcysteine (NAC) has the ability to cause statistically significant diminishment in the in vitro formation of irreversibly sickled cells (ISCs) at concentrations greater than 250 μmol/L. Other antioxidants, approved for human use (cysteamine, succimer, dimercaprol), were not efficacious. NAC had the ability to cause statistically significant conversion of ISCs formed in vivo back to the biconcave shape. NAC was also shown to reduce the formation of dense cells and increase the available thiols in β-actin. We showed that diminishing reduced glutathione (GSH), by treatment with 1-chloro-2,4-dinitrobenzene, resulted in increased dense cells. We conclude the NAC blocks dense cell formation and ISC formation by targeting channels involved in cellular dehydration and β-actin, respectively. The efficacy of NAC is probably due to its combined antioxidant activity and ability to increase intracellular GSH.

The Efficacy of Reducing Agents or Antioxidants in Blocking the Formation of Dense Cells and Irreversibly Sickled Cells In Vitro

Blood ◽  
1998 ◽  
Vol 91 (11) ◽  
pp. 4373-4378 ◽  
Author(s):  
Xunda A. Gibson ◽  
Archil Shartava ◽  
Jonah McIntyre ◽  
Carlos A. Monteiro ◽  
Yalin Zhang ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Reduced Glutathione ◽  
Cell Formation ◽  
Reducing Agents ◽  
Cellular Dehydration ◽  
Dense Cell ◽  
Human Use

We show that N-acetylcysteine (NAC) has the ability to cause statistically significant diminishment in the in vitro formation of irreversibly sickled cells (ISCs) at concentrations greater than 250 μmol/L. Other antioxidants, approved for human use (cysteamine, succimer, dimercaprol), were not efficacious. NAC had the ability to cause statistically significant conversion of ISCs formed in vivo back to the biconcave shape. NAC was also shown to reduce the formation of dense cells and increase the available thiols in β-actin. We showed that diminishing reduced glutathione (GSH), by treatment with 1-chloro-2,4-dinitrobenzene, resulted in increased dense cells. We conclude the NAC blocks dense cell formation and ISC formation by targeting channels involved in cellular dehydration and β-actin, respectively. The efficacy of NAC is probably due to its combined antioxidant activity and ability to increase intracellular GSH.

Fine Structural Changes in the Microvasculature of the Mouse Pinna: Aging and Radiation Injury

1974 ◽  
Vol 32 ◽  
pp. 54-55
Author(s):  
S. Phyllis Steamer ◽  
Rosemarie L. Devine
Keyword(s):  
Structural Changes ◽  
Radiation Treatment ◽  
Arterial Stenosis ◽  
Ultrastructural Changes ◽  
Vascular Effects ◽  
Microvascular Changes ◽  
Surrounding Connective Tissue ◽  
Fission Neutrons ◽  
Total Body

The importance of radiation damage to the skin and its vasculature was recognized by the early radiologists. In more recent studies, vascular effects were shown to involve the endothelium as well as the surrounding connective tissue. Microvascular changes in the mouse pinna were studied in vivo and recorded photographically over a period of 12-18 months. Radiation treatment at 110 days of age was total body exposure to either 240 rad fission neutrons or 855 rad 60Co gamma rays. After in vivo observations in control and irradiated mice, animals were sacrificed for examination of changes in vascular fine structure. Vessels were selected from regions of specific interest that had been identified on photomicrographs. Prominent ultrastructural changes can be attributed to aging as well as to radiation treatment. Of principal concern were determinations of ultrastructural changes associated with venous dilatations, segmental arterial stenosis and tortuosities of both veins and arteries, effects that had been identified on the basis of light microscopic observations. Tortuosities and irregularly dilated vein segments were related to both aging and radiation changes but arterial stenosis was observed only in irradiated animals.

Induction and Differentiation of Dental Epithelium in Vivo and in Vitro

1982 ◽  
Vol 40 ◽  
pp. 142-145
Author(s):  
E. J. Kollar
Keyword(s):  
Connective Tissue ◽  
Oral Mucosa ◽  
Basal Lamina ◽  
Functional Derivatives ◽  
Specific Source ◽  
Dental Epithelium ◽  
Connective Tissue Stroma

The differentiation and maintenance of many specialized epithelial structures are dependent on the underlying connective tissue stroma and on an intact basal lamina. These requirements are especially stringent in the development and maintenance of the skin and oral mucosa. The keratinization patterns of thin or thick cornified layers as well as the appearance of specialized functional derivatives such as hair and teeth can be correlated with the specific source of stroma which supports these differentiated expressions.

Ultrastructural Correlations between Clonal Human Tumor Colonies and in Vivo Neoplasms

1982 ◽  
Vol 40 ◽  
pp. 210-211
Author(s):  
M.J. Murphy ◽  
R.R. Price ◽  
J.C. Sloman
Keyword(s):  
Cultured Cells ◽  
Human Tumor ◽  
Cell Type ◽  
Tumor Mass ◽  
Initial Cell ◽  
Cloning Assay ◽  
Human Tumor Cloning ◽  
The Relationship

The in vitro human tumor cloning assay originally described by Salmon and Hamburger has been applied recently to the investigation of differential anti-tumor drug sensitivities over a broad range of human neoplasms. A major problem in the acceptance of this technique has been the question of the relationship between the cultured cells and the original patient tumor, i.e., whether the colonies that develop derive from the neoplasm or from some other cell type within the initial cell population. A study of the ultrastructural morphology of the cultured cells vs. patient tumor has therefore been undertaken to resolve this question. Direct correlation was assured by division of a common tumor mass at surgical resection, one biopsy being fixed for TEM studies, the second being rapidly transported to the laboratory for culture.

Structural analysis of the photosynthetic membrane from Ectothiorhodospira halochloris

1983 ◽  
Vol 41 ◽  
pp. 740-741
Author(s):  
H. Engelhardt ◽  
R. Guckenberger ◽  
W. Baumeister
Keyword(s):  
Lattice Structure ◽  
Bacterial Species ◽  
Hexagonal Lattice ◽  
Reaction Centre ◽  
Photosynthetic Membrane ◽  
Rhodopseudomonas Viridis ◽  
Photosynthetic Membranes ◽  
Ectothiorhodospira Halochloris ◽  
Main Components

Bacterial photosynthetic membranes contain, apart from lipids and electron transport components, reaction centre (RC) and light harvesting (LH) polypeptides as the main components. The RC-LH complexes in Rhodopseudomonas viridis membranes are known since quite seme time to form a hexagonal lattice structure in vivo; hence this membrane attracted the particular attention of electron microscopists. Contrary to previous claims in the literature we found, however, that 2-D periodically organized photosynthetic membranes are not a unique feature of Rhodopseudomonas viridis. At least five bacterial species, all bacteriophyll b - containing, possess membranes with the RC-LH complexes regularly arrayed. All these membranes appear to have a similar lattice structure and fine-morphology. The lattice spacings of the Ectothiorhodospira haloohloris, Ectothiorhodospira abdelmalekii and Rhodopseudomonas viridis membranes are close to 13 nm, those of Thiocapsa pfennigii and Rhodopseudomonas sulfoviridis are slightly smaller (∼12.5 nm).

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