Vectorial transport of proteins by membrane-bound ribosomes of nongrowing and growing Jerusalem artichoke tuber cells

1978 ◽  
Vol 56 (3) ◽  
pp. 167-173
Author(s):  
Joachim Sparkuhl ◽  
George Setterfield
Keyword(s):  
Reductase Activity ◽  
Jerusalem Artichoke ◽  
Jerusalem Artichoke Tuber ◽  
Protease Digestion ◽  
Associated Proteins ◽  
Membrane Bound ◽  
Nadh Cytochrome ◽  
Vectorial Transport

Both nongrowing (water-incubated) and growing (hormonally stimulated) Jerusalem artichoke tuber cells contain membrane-bound (mb) ribosomes. Using a rapid flotation procedure, a membrane fraction was prepared from both types of cells. This fraction was enriched in mb ribosomes, contained NADH cytochrome c reductase activity, had RNA:phospholipid and RNA:protein ratios similar to those reported for rough microsomes from animal tissues, and supported synthesis of preinitiated proteins in vitro. Using puromycin and detergent release, vectorial transport of labelled polypeptides was measured in the in vitro system. Of proteins made by mb ribosomes from nongrowing cells, only 12% remained associated with microsome membranes following chain termination. The comparable figure for proteins from mb ribosomes of growing tissue was 42%. The membrane-associated proteins were preferentially protected from protease digestion. Some possible reasons are suggested for the correlation between cell growth and the association of newly synthesized proteins with microsomes. The role of proteins synthesized by mb ribosomes but not vectorially transported, in both growing and nongrowing cells, is unknown.

scholarly journals Membrane-associated phase separation: organization and function emerge from a two-dimensional milieu

2021 ◽  
Author(s):  
Jonathon A Ditlev
Keyword(s):  
Phase Separation ◽  
Cell Biology ◽  
Cellular Environment ◽  
Condensate Formation ◽  
Associated Proteins ◽  
Available Technology ◽  
And Function ◽  
Surrounding Membrane

Abstract Liquid‒liquid phase separation (LLPS) of biomolecules has emerged as an important mechanism that contributes to cellular organization. Phase separated biomolecular condensates, or membrane-less organelles, are compartments composed of specific biomolecules without a surrounding membrane in the nucleus and cytoplasm. LLPS also occurs at membranes, where both lipids and membrane-associated proteins can de-mix to form phase separated compartments. Investigation of these membrane-associated condensates using in vitro biochemical reconstitution and cell biology has provided key insights into the role of phase separation in membrane domain formation and function. However, these studies have generally been limited by available technology to study LLPS on model membranes and the complex cellular environment that regulates condensate formation, composition, and function. Here, I briefly review our current understanding of membrane-associated condensates, establish why LLPS can be advantageous for certain membrane-associated condensates, and offer a perspective for how these condensates may be studied in the future.

Anti-Aging Effect of Siraitia grosuenorii by Enhancement of Hematopoietic Stem Cell Function

2016 ◽  
Vol 44 (04) ◽  
pp. 803-815 ◽  
Author(s):  
Lin Bai ◽  
Guiying Shi ◽  
Yajun Yang ◽  
Wei Chen ◽  
Lianfeng Zhang
Keyword(s):  
Aging Process ◽  
Cell Function ◽  
Whooping Cough ◽  
Aging Effect ◽  
Guangxi Province ◽  
Facs Analysis ◽  
Hematopoietic Stem ◽  
Associated Proteins

Anti-aging has always been a popular topic, and there are many claims about the existence of factors that can slow, stop, or even reverse the aging process. Siraitia grosuenorii, a local fruit in china, has been used for the treatment of gastritis, sore throats, and whooping cough in traditional Chinese medicine. The individuals who took the juice of Siraitia grosuenorii regularly had increased longevity in the Guangxi Province, which is located in the Southern part of China. In this paper, we fed mice with Siraitia grosuenorii for 10 months to identify the role of Siraitia grosuenorii in anti-aging and to investigate its corresponding mechanism. The results showed that mice fed with Siraitia grosuenorii displayed a slower aging process. The extension of the aging process was due to the enhanced function of HSCs. FACS analysis showed that the number of LSKs, LT-HSCs, ST-HSCs and MPPs from Siraitia grosuenorii mice was decreased. In vitro, a clonigenic assay showed that LT-HSCs from Siraitia grosuenorii mice increased the ability of self-renewal. Moreover, Siraitia grosuenorii mice maintained the quiescence of LSKs, decreased the level of ROS and reduced the amount of senescence associated β-gal positive cells. Furthermore, Siraitia grosuenorii mice decreased the expression of senescence-associated proteins. Siraitia grosuenorii maintained quiescence, decreased senescence and enhanced the function of HSCs, slowing the aging process of mice.

scholarly journals Studies in vitro on the effects of 1H,2H,4H(5H)-octafluorocyclohexane and 1H,4H(2H)-nonafluorocyclohexane on enzymes and organelles

1969 ◽  
Vol 114 (4) ◽  
pp. 785-792 ◽  
Author(s):  
Jayasree Nath ◽  
H G Bray
Keyword(s):  
Adenosine Triphosphatase ◽  
Marked Decrease ◽  
Reductase Activity ◽  
Electron Microscopic Examination ◽  
Electron Microscopic ◽  
Toxic Compound ◽  
Marked Inhibition ◽  
Liver Homogenates ◽  
Nadh Cytochrome

A comparison has been made of the effect of 1H,2H,4H(5H)-octafluorocyclohexane, which is highly toxic (LD50 17mg./kg. in rats), and of 1H,4H(2H)-nonafluorocyclohexane, which is relatively non-toxic (LD50>440mg./kg. in rats), on the respiration of rat liver homogenates and mitochondria in vitro. 1H,2H,4H(5H)-Octafluorocyclohexane strongly inhibited the respiration of both homogenates and mitochondria, but neither compound had any significant effect on glycolysis or on glutamate dehydrogenase or NADH–cytochrome c reductase activity. 1H,2H,4H(5H)-Octafluorocyclohexane, however, caused a very marked inhibition of cytochrome oxidase activity, causing an almost complete lesion in this region of the respiratory chain. 1H,4H(2H)-Nonafluorocyclohexane was without effect in this respect. A marked decrease in turbidity of mitochondrial suspensions at 520nm. was caused by addition of both compounds, the effect being greater with 1H,2H,4H(5H)-octafluorocyclohexane. ATP, Mg2+ and bovine serum albumin did not reverse these changes. Mitochondrial adenosine triphosphatase activity was increased twofold by the toxic compound, but only slightly by the non-toxic compound. Electron-microscopic examination of mitochondria treated with 1H,2H,4H(5H)-octafluorocyclohexane revealed gross morphological damage, whereas the effect of 1H,4H(2H)-nonafluorocyclohexane appeared to be merely to cause swelling. The results obtained account, to some extent at any rate, for the toxic effects of 1H,2H,4H(5H)-octafluorocyclohexane.

scholarly journals Medawar’s PostEra: Galectins Emerged as Key Players During Fetal-Maternal Glycoimmune Adaptation

2021 ◽  
Vol 12 ◽  
Author(s):  
Ellen Menkhorst ◽  
Nandor Gabor Than ◽  
Udo Jeschke ◽  
Gabriela Barrientos ◽  
Laszlo Szereday ◽  
...  
Keyword(s):  
Immune Cell ◽  
Successful Pregnancy ◽  
Fetal Health ◽  
The Past ◽  
Mammalian Embryogenesis ◽  
Carbohydrate Ligands ◽  
Membrane Bound

Lectin-glycan interactions, in particular those mediated by the galectin family, regulate many processes required for a successful pregnancy. Over the past decades, increasing evidence gathered from in vitro and in vivo experiments indicate that members of the galectin family specifically bind to both intracellular and membrane bound carbohydrate ligands regulating angiogenesis, immune-cell adaptations required to tolerate the fetal semi-allograft and mammalian embryogenesis. Therefore, galectins play important roles in fetal development and placentation contributing to maternal and fetal health. This review discusses the expression and role of galectins during the course of pregnancy, with an emphasis on maternal immune adaptions and galectin-glycan interactions uncovered in the recent years. In addition, we summarize the galectin fingerprints associated with pathological gestation with particular focus on preeclampsia.

Dissociation of FAD from the NAD(P)H-Nitrate Reductase Complex from Ankistrodesmus braunii and Role of Flavin in Catalysis

1982 ◽  
Vol 37 (1-2) ◽  
pp. 24-30 ◽  
Author(s):  
Miguel A. De la Rosa ◽  
Antonio J. Márquez ◽  
José M. Vega
Keyword(s):  
Nitrate Reductase ◽  
Reductase Activity ◽  
Prosthetic Group ◽  
Original Activity ◽  
Enzyme Preparations ◽  
Fluorescence Studies ◽  
Transport Chain ◽  
Sulphydryl Groups ◽  
Nadh Cytochrome

Ankistrodesmus braunii NAD(P)H-nitrate reductase is a complex hemoflavomolybdoprotein composed by eight similar subunits. The flavin prosthetic group, identified as FAD, is essential for the NAD(P)H-dependent activities of the complex, and is located before the heme chromo- phore in the enzyme electron transport chain from reduced pyridine nucleotides to nitrate. Fluorescence studies indicate that nitrate reductase can dissociate about 80% of its FAD by incubation at room temperature, the flavin dissociation being followed by a parallel decrease of NADH-nitrate reductase activity. Dissociation of FAD from the protein is easily increased by dilution or prolonged dialysis of the enzyme preparations. However, exogenous FAD specifically prevents the dissociation of enzyme-bound flavin, and protects the NAD(P)H-dependent activities. The Km for FAD, as a protector of NADH-cytochrome c reductase activity, is 4 nᴍ. In addition, dithioerythritol also prevents the flavin dissociation, and therefore the presence of free sulphydryl groups in the FAD-domain is suggested. FAD-depleted nitrate reductase, obtained by several methods, is unable to recover its original activity when incubated in the presence of FAD alone or with thiols.

Action des rayons gamma du Cobalt 60 sur la teneur en acides nucléiques et l'histogenèse des tissus de tubercule de topinambour cultivés in vitro

1983 ◽  
Vol 61 (5) ◽  
pp. 1448-1455 ◽  
Author(s):  
Janine Schaeverbeke-Sacré ◽  
Béatrice Matheron
Keyword(s):  
Radiation Dose ◽  
Gamma Irradiation ◽  
Gamma Rays ◽  
Cytological Study ◽  
Jerusalem Artichoke ◽  
Dna And Rna ◽  
Jerusalem Artichoke Tuber ◽  
Outer Area

DNA and RNA contents are studied in Jerusalem artichoke tuber explants cultured in vitro after gamma irradiation (0–5 × 105 rads (1 rad = 10 mGy)). The lower part of the explants is stimulated as soon as in contact with the medium. This stimulated area is still able to synthesize DNA and RNA up to 104 rads. An histological and cytological study shows that tissue neoformations can be observed up to 6000 rads in this outer area and that gamma rays seem to keep the cells in a "premitotic" state for a longer or shorter period according to the applied radiation dose.

scholarly journals Manganese Induces Oxidative Stress, Redox State Unbalance and Disrupts Membrane Bound ATPases on Murine Neuroblastoma Cells In Vitro: Protective Role of Silymarin

2011 ◽  
Vol 36 (8) ◽  
pp. 1546-1557 ◽  
Author(s):  
Yassine Chtourou ◽  
Khaled Trabelsi ◽  
Hamadi Fetoui ◽  
Ghada Mkannez ◽  
Héla Kallel ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Redox State ◽  
Neuroblastoma Cells ◽  
Protective Role ◽  
Murine Neuroblastoma ◽  
Membrane Bound

scholarly journals Resolution of Distinct Membrane-Bound Enzymes from Enterobacter cloacae SLD1a-1 That Are Responsible for Selective Reduction of Nitrate and Selenate Oxyanions

2006 ◽  
Vol 72 (8) ◽  
pp. 5173-5180 ◽  
Author(s):  
Helen Ridley ◽  
Carys A. Watts ◽  
David J. Richardson ◽  
Clive S. Butler
Keyword(s):  
Nitrate Reductase ◽  
Reductase Activity ◽  
Selective Reduction ◽  
Enterobacter Cloacae ◽  
Anaerobic Growth ◽  
Elemental Selenium ◽  
Membrane Bound ◽  
Membrane Bound Enzymes ◽  
Distinct Membrane

ABSTRACT Enterobacter cloacae SLD1a-1 is capable of reductive detoxification of selenate to elemental selenium under aerobic growth conditions. The initial reductive step is the two-electron reduction of selenate to selenite and is catalyzed by a molybdenum-dependent enzyme demonstrated previously to be located in the cytoplasmic membrane, with its active site facing the periplasmic compartment (C. A. Watts, H. Ridley, K. L. Condie, J. T. Leaver, D. J. Richardson, and C. S. Butler, FEMS Microbiol. Lett. 228:273-279, 2003). This study describes the purification of two distinct membrane-bound enzymes that reduce either nitrate or selenate oxyanions. The nitrate reductase is typical of the NAR-type family, with α and β subunits of 140 kDa and 58 kDa, respectively. It is expressed predominantly under anaerobic conditions in the presence of nitrate, and while it readily reduces chlorate, it displays no selenate reductase activity in vitro. The selenate reductase is expressed under aerobic conditions and expressed poorly during anaerobic growth on nitrate. The enzyme is a heterotrimeric (αβγ) complex with an apparent molecular mass of ∼600 kDa. The individual subunit sizes are ∼100 kDa (α), ∼55 kDa (β), and ∼36 kDa (γ), with a predicted overall subunit composition of α3β3γ3. The selenate reductase contains molybdenum, heme, and nonheme iron as prosthetic constituents. Electronic absorption spectroscopy reveals the presence of a b-type cytochrome in the active complex. The apparent Km for selenate was determined to be ∼2 mM, with an observed V max of 500 nmol SeO4 2− min−1 mg−1 (k cat, ∼5.0 s−1). The enzyme also displays activity towards chlorate and bromate but has no nitrate reductase activity. These studies report the first purification and characterization of a membrane-bound selenate reductase.

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