Light-Dependent Metabolism of Carbon Compounds by Mesophyll Chloroplasts from Plants with the C4 Pathway of Photosynthesis

1974 ◽  
Vol 1 (1) ◽  
pp. 51 ◽  
Author(s):  
T Kagawa ◽  
MD Hatch
Keyword(s):  
Outer Membrane ◽  
Oxygen Evolution ◽  
Carbon Metabolism ◽  
Initial Rate ◽  
Dihydroxyacetone Phosphate ◽  
C4 Species ◽  
Carbon Compounds ◽  
C4 Pathway

This paper describes the capacities of intact mesophyll chloroplasts prepared from Atviplex spongiosa and maize for the light-dependent metabolism of carbon compounds. Illuminated chloroplasts converted pyruvate to phosphoenolpyruvate but the initial rate was maintained only when either 3-phosphoglycerate or methylviologen was added. Light-dependent oxygen evolution was observed when 3-phosphoglycerate or oxaloacetate was added to chloroplasts, and the concomitant production of dihydroxyacetone phosphate or malate was observed. The addition of ADP or NADP or both did not produce increases in these activities. Addition of the photophosphorylation uncoupler methylamine stimulated the rate of oxaloacetate reduction and inhibited the conversion of 3-phosphoglycerate to dihydroxyacetone phosphate. These chloroplasts were not capable of oxygen evolution upon the addition of bicarbonate and did not fix CO2. The data also provided information about minimum rates of influx or efflux of metabolites through the chloroplast outer membrane. These studies confirmed that mesophyll chloroplasts of C4 species are unique in terms of their cap- acities for carbon metabolism. These activities are discussed in relation to the role of mesophyll chloroplasts in C4-pathway photosynthesis.

The Role of Sodium in the Conversion of Pyruvate to Phosphoenolpyruvate in Mesophyll Chloroplasts of C4 Plants

1996 ◽  
Vol 23 (2) ◽  
pp. 171 ◽  
Author(s):  
PF Brownell ◽  
LM Bielig
Keyword(s):  
Oxygen Evolution ◽  
Malic Enzyme ◽  
Small Samples ◽  
Panicum Miliaceum ◽  
Tight Coupling ◽  
Irreversible Damage ◽  
C4 Species ◽  
The Hill

PEP formation from pyruvate was determined in mesophyll chloroplasts mechanically isolated from sodium-deficient and sodium-replete plants of the NADP malic enzyme-type C4 species, Kochia trichophylla. An extremely sensitive method for estimating PEP was developed which permitted determination of picomole quantities of PEP in small samples taken sequentially from the mesophyll chloroplast suspension concurrently with observations on oxygen evolution. It was shown that PEP formation requires light and depends upon the intactness of the chloroplasts. The rate of formation of PEP from pyruvate increased in the presence of the Hill reagent, oxaloacetate, thus indicating its dependence on non-cyclic photophosphorylation for the supply of ATP required in the conversion of pyruvate to PEP. The optimum inorganic phosphate concentration for PEP formation was approximately 16 mM. The rates of oxygen evolution and PEP formation were equivalent at concentrations of pyruvate up to 20 mM, suggesting tight coupling between electron transport and phosphorylation. In both Kochia trichophylla and the NAD malic enzyme-type, Panicum miliaceum, the rates of PEP formation were greater in the mesophyll chloroplasts from sodium-replete than from sodium-deficient plants. Chloroplasts resuspended in 'sodium-free'media containing less than 30 μM (0.7 ppm) sodium showed reduced rates of PEP formation compared with chloroplasts resuspended in media to which 1.0 mM (23 ppm) sodium had been added. Both media contained 10 mM 'sodium-free' KCI. These results indicate that sodium ions may be required to maintain the functional integrity of the mesophyll chloroplasts and that irreversible damage is sustained when sodium is absent during their isolation.

A ROLE OF PROTEINS OF THE OUTER MEMBRANE OF Shewanella oneidensis MR-1 BACTERIA IN FORMATION AND STABILIZATION OF SILVER SULFIDE NANOPARTICLES

2015 ◽  
pp. 41-48 ◽  
Author(s):  
T. A. Voeikova ◽  
A. S. Shebanova ◽  
Yu. D. Ivanov ◽  
A. L. Kaysheva ◽  
L. M. Novikova ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Shewanella Oneidensis ◽  
Silver Sulfide ◽  
Silver Sulfide Nanoparticles

Effect of various cations on the initial rate of formation of peroxodisulphates

1980 ◽  
Vol 45 (8) ◽  
pp. 2272-2282 ◽  
Author(s):  
Jan Balej ◽  
Martin Kadeřávek
Keyword(s):  
Sulphuric Acid ◽  
Oxygen Evolution ◽  
Anodic Polarization ◽  
Initial Rate ◽  
Degree Of Conversion ◽  
Polarization Curves ◽  
Mixed Solutions ◽  
Low Degree ◽  
Partial Polarization

Preparation of peroxodisulphates by electrolysis of mixed solutions of sulphuric acid and various sulphates was studied at low degree of conversion; the partial polarization curves of peroxodisulphate formation and of oxygen evolution obtained from the overall anodic polarization curves and current yields of the principal anodic processes were examined. The mechanism of the effect of various cations on the rate of anodic formation of peroxodisulfates is discussed.

scholarly journals A structurally versatile nickel phosphite acting as a robust bifunctional electrocatalyst for overall water splitting

2018 ◽  
Vol 11 (5) ◽  
pp. 1287-1298 ◽  
Author(s):  
Prashanth W. Menezes ◽  
Chakadola Panda ◽  
Stefan Loos ◽  
Florian Bunschei-Bruns ◽  
Carsten Walter ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Water Splitting ◽  
Oxygen Evolution ◽  
Bifunctional Electrocatalyst ◽  
Overall Water Splitting

The mechanistically distinct and synergistic role of phosphite anions in hydrogen evolution and nickel cations in oxygen evolution have been uncovered for active and durable overall water splitting catalysis in nickel phosphite.

scholarly journals MexAB-OprM Efflux Pump Interaction with the Peptidoglycan of Escherichia coli and Pseudomonas aeruginosa

2021 ◽  
Vol 22 (10) ◽  
pp. 5328
Author(s):  
Miao Ma ◽  
Margaux Lustig ◽  
Michèle Salem ◽  
Dominique Mengin-Lecreulx ◽  
Gilles Phan ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Pseudomonas Aeruginosa ◽  
Cell Division ◽  
Membrane Proteins ◽  
Outer Membrane ◽  
Efflux Pump ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Active Efflux

One of the major families of membrane proteins found in prokaryote genome corresponds to the transporters. Among them, the resistance-nodulation-cell division (RND) transporters are highly studied, as being responsible for one of the most problematic mechanisms used by bacteria to resist to antibiotics, i.e., the active efflux of drugs. In Gram-negative bacteria, these proteins are inserted in the inner membrane and form a tripartite assembly with an outer membrane factor and a periplasmic linker in order to cross the two membranes to expulse molecules outside of the cell. A lot of information has been collected to understand the functional mechanism of these pumps, especially with AcrAB-TolC from Escherichia coli, but one missing piece from all the suggested models is the role of peptidoglycan in the assembly. Here, by pull-down experiments with purified peptidoglycans, we precise the MexAB-OprM interaction with the peptidoglycan from Escherichia coli and Pseudomonas aeruginosa, highlighting a role of the peptidoglycan in stabilizing the MexA-OprM complex and also differences between the two Gram-negative bacteria peptidoglycans.

The role of exudation in chronic subdural hematomas

2007 ◽  
Vol 107 (2) ◽  
pp. 290-295 ◽  
Author(s):  
Mehmet Tokmak ◽  
A. Celal Iplikcioglu ◽  
Sirzat Bek ◽  
Cem Atilla Gökduman ◽  
Mustafa Erdal
Keyword(s):  
Outer Membrane ◽  
Clinical Status ◽  
Ct Scans ◽  
Subdural Hematomas ◽  
The Mean ◽  
Grade 3 ◽  
Age Range ◽  
Exudation Rate

Object Chronic subdural hematomas (SDHs) are a local inflammatory process that causes the formation of a granulation tissue often referred to as the external or outer membrane. This membrane has abnormally permeable macrocapillaries. Therefore, exudation from the macrocapillaries in the outer membrane of chronic SDH may play an important role in the enlargement of chronic SDH. In this study the authors investigated the role of exudation in chronic SDH. Methods The authors examined 24 patients (16 men and eight women; age range 38–86 years [mean age 61.4 years]) with 27 chronic SDHs. The clinical status of the patients was evaluated according to the classification described by Markwalder. The diagnosis was established on computed tomography (CT) scans in all cases. The authors also used the Nomura Classification for judging the lesion's appearance on CT scans. Immediately after the diagnosis, all patients were administered 20 mCi (740 mBq) technetium-99m human serum albumin. Four hours later, blood and SDH samples were taken and radioactivity levels were measured in each. The ratio of activity of the samples taken from chronic SDH to the radioactivity of blood was determined as a percentage and defined as the exudation rate. On the follow-up CT scan obtained on postoperative Day 20, subdural collections thicker than 5 mm were determined to be a reaccumulation. Results The correlations between the exudation rate and age of the patients, clinical grades, CT appearances, and amount of reaccumulation were investigated. In this series the average exudation rate was 13.24% (range 2.05–28.88%). The mean exudation rates according to the clinical grades assigned to patients were as follows: Grade 0, 8.67 ± 5.64% (three patients); Grade 1, 5.07 ± 1.43% (eight patients); Grade 2, 17.87 ± 3.73% (seven patients); and Grade 3, 19.65 ± 7.67% (six patients). Exudation rates in patients with Grades 2 and 3 were significantly higher than those in Grades 0 and 1 (p < 0.05). The mean exudation rates according to the lesion's appearance on CT scans were found as follows: hypodense appearance, 6.55 ± 4.52% (eight patients); isodense appearance, 11.07 ± 6.32% (five patients); hyperdense appearance, 19.47 ± 13.61% (three patients); and mixed-density appearance, 17.40 ± 5.80% (nine patients). The differences among the groups were significant (p < 0.05). The average exudation rate was statistically higher in the patients with reaccumulation (16.30 ± 8.16%) than that in the patients without reaccumulation (9.96 ± 6.84%) (p < 0.05). Conclusions The exudation rate in chronic SDH is correlated with a higher clinical grade (Markwalder Grade 2 or 3), mixed-density CT appearance, and reaccumulation. Therefore, exudation from macrocapillaries in the outer membrane of chronic SDH probably plays an important role in the pathophysiology and the growth of chronic SDH.

scholarly journals Role of Phosphatidylethanolamine in the Biogenesis of Mitochondrial Outer Membrane Proteins

2013 ◽  
Vol 288 (23) ◽  
pp. 16451-16459 ◽  
Author(s):  
Thomas Becker ◽  
Susanne E. Horvath ◽  
Lena Böttinger ◽  
Natalia Gebert ◽  
Günther Daum ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Outer Membrane ◽  
Outer Membrane Proteins ◽  
Proper Function ◽  
Mitochondrial Outer Membrane ◽  
Tom Complex ◽  
Precursor Proteins ◽  
Helical Proteins ◽  
The Stability

The mitochondrial outer membrane contains proteinaceous machineries for the import and assembly of proteins, including TOM (translocase of the outer membrane) and SAM (sorting and assembly machinery). It has been shown that the dimeric phospholipid cardiolipin is required for the stability of TOM and SAM complexes and thus for the efficient import and assembly of β-barrel proteins and some α-helical proteins of the outer membrane. Here, we report that mitochondria deficient in phosphatidylethanolamine (PE), the second non-bilayer-forming phospholipid, are impaired in the biogenesis of β-barrel proteins, but not of α-helical outer membrane proteins. The stability of TOM and SAM complexes is not disturbed by the lack of PE. By dissecting the import steps of β-barrel proteins, we show that an early import stage involving translocation through the TOM complex is affected. In PE-depleted mitochondria, the TOM complex binds precursor proteins with reduced efficiency. We conclude that PE is required for the proper function of the TOM complex.

scholarly journals Role of Hemagglutinin Surface Density in the Initial Stages of Influenza Virus Fusion: Lack of Evidence for Cooperativity

2000 ◽  
Vol 74 (6) ◽  
pp. 2714-2720 ◽  
Author(s):  
Susanne Günther-Ausborn ◽  
Pieter Schoen ◽  
Ingrid Bartoldus ◽  
Jan Wilschut ◽  
Toon Stegmann
Keyword(s):  
Influenza Virus ◽  
Surface Density ◽  
Initial Rate ◽  
Fusion Activity ◽  
Cooperative Action ◽  
Lipid Ratio ◽  
Virus Fusion ◽  
Influenza Virus Hemagglutinin ◽  
Optimal Fusion

ABSTRACT Membrane fusion mediated by influenza virus hemagglutinin (HA) is believed to proceed via the cooperative action of multiple HA trimers. To determine the minimal number of HA trimers required to trigger fusion, and to assess the importance of cooperativity between these HA trimers, we have generated virosomes containing coreconstituted HAs derived from two strains of virus with different pH dependencies for fusion, X-47 (optimal fusion at pH 5.1; threshold at pH 5.6) and A/Shangdong (optimal fusion at pH 5.6; threshold at pH 6.0), and measured fusion of these virosomes with erythrocyte ghosts by a fluorescence lipid mixing assay. Virosomes with different X-47-to-A/Shangdong HA ratios, at a constant HA-to-lipid ratio, showed comparable ghost-binding activities, and the low-pH-induced conformational change of A/Shangdong HA did not affect the fusion activity of X-47 HA. The initial rate of fusion of these virosomes at pH 5.7 increased directly proportional to the surface density of A/Shangdong HA, and a single A/Shangdong trimer per virosome appeared to suffice to induce fusion. The reciprocal of the lag time before the onset of fusion was directly proportional to the surface density of fusion-competent HA. These results support the notion that there is no cooperativity between HA trimers during influenza virus fusion.

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