Role Of Manganese Research Articles

The role of manganese in promoting multimerization and assembly of human immunodeficiency virus type 1 integrase as a catalytically active complex on immobilized long terminal repeat substrates.

The integration of a DNA copy of the viral genome into the genome of the host cell is an essential step in the replication of all retroviruses. Integration requires two discrete biochemical reactions; specific processing of each viral long terminal repeat terminus or donor substrate, and a DNA strand transfer step wherein the processed donor substrate is joined to a nonspecific target DNA. Both reactions are catalyzed by a virally encoded enzyme, integrase. A microtiter assay for the strand transfer activity of human immunodeficiency virus type 1 integrase which uses an immobilized oligonucleotide as the donor substrate was previously published (D. J. Hazuda, J. C. Hastings, A. L. Wolfe, and E. A. Emini, Nucleic Acids Res. 22;1121-1122, 1994). We now describe a series of modifications to the method which facilitate study of both the nature and the dynamics of the interaction between integrase and the donor DNA. The enzyme which binds to the immobilized donor is shown to be sufficient to catalyze strand transfer with target DNA substrates added subsequent to assembly; in the absence of the target substrate, the complex was retained on the donor in an enzymatically competent state. Assembly required high concentrations of divalent cation, with optimal activity achieved at 25 mM MnCl2. In contrast, preassembled complexes catalyzed strand transfer equally efficiently in either 1 or 25 mM MnCl2, indicating mechanistically distinct functions for the divalent cation in assembly and catalysis, respectively. Prior incubation of the enzyme in 25 mM MnCl2 was shown to promote the multimerization of integrase in the absence of a DNA substrate and alleviate the requirement for high concentrations of divalent cation during assembly. The superphysiological requirement for MnCl2 may, therefore, reflect an insufficiency for functional self-assembly in vitro. Subunits were observed to exchange during the assembly reaction, suggesting that multimerization can occur either before or coincident with but not after donor binding. These studies both validate and illustrate the utility of this novel methodology and suggest that the approach may be generally useful in characterizing other details of this biochemical reaction.

The role of manganese in chronic hepatic encephalopathy

The role of manganese in chronic hepatic encephalopathy

On the role of manganese in photosynthetic water oxidation

On the role of manganese in photosynthetic water oxidation

Serum and urinary manganese levels in patients with Parkinson's disease

To elucidate the possible role of manganese in the risk of developing Parkinson's disease (PD), we compared serum levels of manganese, and 24-h manganese excretion by urine in 29 PD patients and in 27 matched controls. We also measured chromium and cobalt in the same samples. All these values did not differ significantly between the groups, they were not influenced by antiparkinsonian drugs, and they did not correlate with age, age at onset and duration of the PD, scores of the Unified PD Rating Scale or the Hoehn & Yahr staging in the PD group. These results might suggest that serum levels and urinary excretion of manganese are apparently unrelated to the risk of developing PD.

Antioxidants inhibit ethanol-induced gastric injury in the rat. Role of manganese, glycine, and carotene.

Oxygen-derived radicals are implicated in the pathogenesis of tissue damage and ulcerogenesis. This study aimed to examine the effect of manganese, glycine, and carotene, oxygen radical scavengers, on ethanol-induced gastric lesions in the rat and on ethanol cytotoxicity in epithelial cell culture. MnCl2 + glycine (12.5-50 mg/rat) were injected subcutaneously up to 6 h before oral administration of 1 ml of 96% ethanol, and 0.5 ml carrot juice or beta-carotene was given orally 30 min before the ethanol. Mucosal injury was evaluated 1 h later by gross and microscopic scoring. The effect of Mn2+ and carrot juice was also tested in monolayers of radiolabeled epithelial cells exposed to H2O2 + ethanol injury as expressed by the extent of the isotope leakage. Mn2+ and glycine pretreatment dose-dependently reduced ethanol-induced gastric lesion formation. Protection was maximal when treatment was applied 4 h before the insult. Gross damage was also markedly prevented by pretreatment with carotenes and dimethylthiourea (DMTU, 75 mg/kg intraperitoneally) but not by allopurinol. Mixtures of subtoxic concentrations of ethanol and H2O2 were highly lethal for epithelial cell monolayers. In this model, cell death was markedly attenuated by catalase, DMTU, Mn2+, and carrot juice. Ethanol-induced gastric mucosal damage may involve generation of oxygen-derived radicals, independent of the xanthine oxidase system. By acting as oxygen radical scavengers, Mn2+, glycine, and carotenes, like catalase and DMTU, provide significant gastroprotection.

Mn-Catalyzed Oxidation of Multiple-Ringed Aromatics

The role of manganese (Mn) oxides in catalyzing the abiotic oxidation of polynuclear aromatic compounds (PNAs) has been investigated by monitoring the oxidation of dihydrodiol and dione PNAs and corresponding reduction of Mn in an aqueous environment. 1,4-, 1,3-, and 2,3-naphthalenediol, 1,4-naphthoquinone, and l,4-dihydroxy-9,10-anthracenedione (Quinizarin) were oxidized in an oxic, aqueous environment, where each of these organic compounds is soluble in water, except Quinizarin. A mathematical model is presented, which describes the redox reactions, and suggests that electron transfer/organic release from the oxide surface is rate limiting with the reaction apparently proceeding through a free-radical formation. Results indicate significant oxidation of the organics, that the oxidation of the diols is kinetically more favorable than that of the dione, and that lower molecular weight PNAs containing diol and dione functional groups are susceptible to abiotic-catalyzed oxidation, thereby suggesting that progressively more complex PNA molecules may also be susceptible to oxidation.

Addition of manganese to iron catalysts supported on silicalite-1 and its effect on CO hydrogenation

The addition of manganese to iron catalysts supported on silicalite-1 increases the selectivity of the catalysts to alkenes in CO hydrogenation. The catalysts were prepared by impregnating the support with metal nitrates followed by calcination and in situ reduction in hydrogen. The Mossbauer spectra of the calcined samples showed that the addition of manganese reduced the size of the α-Fe2O3 particles. This was confirmed by XRD and TPR results. The active phase consists of Hagg carbide and some oxides of FeI I I, the latter being responsible for the increased alkene formation. The role of manganese is to reduce the particle size of the iron oxide precursor, making carburization unfavourable. This leads to an increase in the amount of the oxide phase in the catalyst, thereby increasing the selectivity to alkenes.

Mechanism of manganese porphyrin-catalyzed oxidation of alkenes. Role of manganese(IV)-oxo species

The mechanism for the bimolecular reaction of meso-tetrakis(2,6-dichlorophenyl)porphinato-oxo-manganese-(IV), [(Cl 8 TPP)Mn IV (O)], with alkenes has been investigated by kinetics and product identification. Kinetic studies were carried out with 11 alkenes (trans-4-methoxystilbene, cis-4-methoxystilbene, 1,4-diphenyl-1,3-butadiene, 4-methoxystyrene, 1,1-diphenylethylene, 4-methylstyrene, 2,3-dimethyl-2-butene, trans-stilbene, cis-stilbene, styrene, 4-acetoxystyrene) in methylene chloride solution (30 o C) in air. The reactivities of the alkenes show that the trans alkenes are slightly more reactive than their cis isomers and that electron releasing substituents slightly favor the reaction

The role of manganese and nitrogen nutrition in the susceptibility of wheat plants to take-all in Western Australia

Five field experiments are described which measured the effect of take-all on grain yield of wheat when 5 levels of manganese fertilizer were applied in a factorial combination with 5 different types of nitrogen fertilizer. Ammonium nitrogen fertilizer, either as ammonium sulphate or ammonium chloride, lowered the severity of take-all. By contrast, sodium nitrate had no effect on the incidence and severity of take-all. Ammonium chloride and ammonium sulphate were equally effective at controlling take-all, suggesting that the chloride or sulphate ion had little or no effect on the disease. Manganese sulphate decreased take-all severity at two trial sites. Where manganese was deficient, an application of manganese lowered the severity of take-all, had no effect on the incidence and increased the dry matter and grain yields of the wheat plants. There were no beneficial effects of applied manganese if the wheat plants were adequately supplied with soil manganese. The results suggest that take-all is more severe where plants are deficient in either manganese or nitrogen. The work also suggests that manganese deficiency is not necessarily the reason why the wheat plants grown on the acid soils of south-west Western Australia are prone to take-all.

The role of manganese in photosynthetic water oxidation

The process of photosynthetic water oxidation to dioxygen under proton release takes place via a sequence of four univalent redox steps in a manganese-containing unit. In this mini-review the current state of knowledge is briefly described with special emphasis on the following topics: (a) the nature of the catalytic site, (b) the structure of the redox chemistry of the manganese-containing active site, (c) the ligand structure and the entry of substrate water into the redox cycle, and (d) problems of the stoichiometry of proton release coupled with individual redox steps and the possible role of other cofactors (Cl−, Ca2+).

The Role of Manganese in Model Systems Related to Lignin Biodegradation

Des etudes electrochimiques et biomimetiques montrent que certains acides carboxyliques stabilisent le manganese(III) en solution aqueuse par formation de complexes. Parmi ces acides, l'acide malonique est le ligand le plus efficace. On montre que les complexes Mn(III)-acide α-hydroxycarboxylique fonctionnent comme oxydants diffusables dans l'oxydation des composes modeles de la lignine et que l'efficacite de ces complexes n'est pas liee directement a leur potentiel redox

A New Functional Test of Manganese Status

There is limited clinical interest in the role ofmanganese in the pathogenesis and therapy of disease despite the fact that some research has shown it to be an important trace mineral. One of the reasons for this may be the difficulty in the accurate measurement of Mn concentration in biological fluids with the expertise and expense required. A functional test for Mn status is described based upon the activation ofisocitrate dehydrogenase by Mn. The results obtained from this test are compared with more conventional indices of Mn status, i.e. serum and sweat concentrations. The possible limitations are discussed along with its advantages as a simple and inexpensive screening test.

Photoactivation of water by p-benzoquinone and the role of manganese(III) complexes in oxygen evolution: molecular orbital theory

Photoactivation of water by p-benzoquinone and the role of manganese(III) complexes in oxygen evolution: molecular orbital theory

Specific role of manganese and magnesium on RNA synthesis in rabbit bone marrow erythroid cell nuclei

Specific roles of manganese (Mn) and magnesium (Mg) on the activities of DNA-dependent RNA polymerases I and II isolated from rabbit bone marrow erythroid cell nuclei were investigated. Three main polymerases were separated from the cell nuclei. When RNA polymerase I and Mg were added to the RNA synthesis assay mixture containing erythroid cell DNA as template, RNA transcription activity was highest, but when Mg was replaced with Mn, denatured calf thymus DNA formed a better template than erythroid cell DNA. In contrast, nucleoplasmic DNA from erythroid cell and liver DNA were the best templates to stimulate RNA transcription when RNA polymerase II and Mn were added to the assay mixture. However, if Mn was replaced with Mg, RNA synthesis activity was drastically reduced when the template was nucleoplasmic DNA of erythroid cell. RNA polymerase I and Mg synthesized GC rich RNA, whereas RNA polymerase II and Mn synthesized AU rich RNA. Sedimentation analysis showed that the molecular weights of the RNA produced by polymerase I were larger when the enzyme was activated with Mg than with Mn, whereas those of the RNA produced by polymerase II were larger with Mn than with Mg. Furthermore, RNA produced by polymerase I and Mg using chromatin as a template hybridized better with nucleolar DNA than with nucleoplasmic DNA, whereas that produced by polymerase II and Mn hybridized better with nucleoplasmic DNA than with nucleolar DNA. These results suggest that RNA synthesis is dependent on the activity of specific RNA polymerases and the presence of specific divalent cations and templates, and that the cofactor and template for RNA polymerase I are, respectively, Mg and the nucleolar DNA of cell nuclei, whereas those for RNA polymerase II are Mn and nucleoplasmic DNA.

A Review of the Role of Manganese in Pine Plantations

SYNOPSIS The literature on the physiological role of manganese in trees is reviewed. Manganese (Mn) deficiency is associated with strongly-podzolised soils and good drainage. Deficiency symptoms and foliar nutrient trace element levels are given for the Southern Cape. Future research should concentrate on soil tests: monitoring of foliar levels in second-rotation stands and the evaluation of enzymatic physiological assay techniques.

Secondary Role of Manganese During Iron Deprivation of Brochothrix thermosphacta

Summary Manganese was found to partially replace the iron requirement of Brochothrix thermosphacta under ironlimiting conditions, during aerobic incubation in minimal medium broth (MMB) at 25°C. Inhibition by iron chelation using 10 μmol/ml ethylenediamine di(o-hydroxyphenyl acetic acid), (EDDA), was partially overcome with the addition of 0.5–4.0 μg/ml ultrapure manganese. Reversal of inhibition was independent of the time at which manganese was added after exposure to EDDA between 0 and 5 hours. Addition of 2.0 or 12.3 μg//ml manganese to MMB had no stimulatory growth effect relative to the control when iron was not limiting. Atomic absorption data indicated that manganese was transported intracellularly in proportion to medium Mn concentration whether or not iron was limiting.

Role of Manganese in Chronic Hemodialysis Patients

Role of Manganese in Chronic Hemodialysis Patients

The electrochemical mechanism of photosystem II functioning in chloroplasts

The electrochemical aspects of oxygen evolution in photosynthesis are considered. A four-electron mechanism is proposed for the photooxidation of water in the reaction center of photosystem II of chloroplasts. It is supposed that water can be oxidized by a reaction center consisting of four chloropyll molecules, a Mn cluster, two pheophytin molecules and several plastoquinone molecules. The catalytic complex responsible for the oxidation of water is assumed to include four manganese ions. Two cations are necessary for the catalytic formation of the hydrated chlorophyll dimer; these can be substituted by other cations of multivalent metals. The partition of protons between the inner and outer side of thylakoid membranes can be controlled by the pool of plastoquinones, lipids, polar groups of proteins and ATP-synthetase. The probability of the four-electron is analyzed thermodynamically and kinetically. The role of manganese in photosynthesis is discussed.

Role of manganese in alloy-porcelain bonding

Role of manganese in alloy-porcelain bonding

A Role for manganese in the Regulation of Soybean Nitrate Reductase Activity?

The effect of manganese nutrient levels and light treatments on nitrate reductase activity (NRA) of soybean leaves was studied. Under dark conditions, soybean Mn-deficient leaves showed higher NRA than normal leaves, using the in vivo and in vitro assays. Under light, the differences in activities depended on the incubation media in the in vivo assay, whereas under the same conditions in the in vitro assay the differences observed between (- Mn)- and ( + Mn)-leaves were lower. In leaf homogenates, MV- and FMNH(2)-NR activities were also reduced in ( + Mn)-leaves in comparison to Mn-limiting leaves but DCPIP-NADH reductase was not affected. Apparently, differences in NRA could be localized on the final step of nitrate reduction, though reactivation by the addition of ferricyanide could not be obtained. Partial purification of NADH-NR-inhibitor from both, (- Mn)- and ( + Mn)-leaves, and activity assays showed lower inhibition rates of NRA by those fractions obtained from the Mn-deficient leaves. On the basis of the results obtained, an indirect role of manganese on the regulation of NRA is proposed.