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E M Massa

Publications and source records attributed to E M Massa.

At least 19 recordsLinked to original sources
PubMed1999

Characterization of an NADH-linked cupric reductase activity from the Escherichia coli respiratory chain.

Previous results from our laboratory have shown that NADH-supported electron flow through the Escherichia coli respiratory chain promotes the reduction of cupric ions to Cu(I), which mediates damage of the respiratory system by hydroperoxides. The aim of this work was to characterize the NADH-linked cupric reductase activity from the E. coli respiratory chain. We have used E. coli strains that either overexpress or are deficient in the NADH dehydrogenase-2 (NDH-2) to demonstrate that this membrane-bound protein catalyzes the electron transfer from NADH to Cu(II), but not to Fe(III). We also show that purified NDH-2 exhibits NADH-supported Cu(II) reductase activity in the presence of either FAD or quinone, but is unable to reduce Fe(III). The K(m) values for free Cu(II) were 32 +/- 5 pM in the presence of saturating duroquinone and 22 +/- 2 pM in the presence of saturating FAD. The K(m) values for NADH were 6.9 +/- 1.5 microM and 6.1 +/- 0.7 microM in the presence of duroquinone and FAD, respectively. The quinone-dependent Cu(II) reduction occurred through both O(*-)(2)-mediated and O(*-)(2)-independent pathways, as evidenced by the partial inhibitory effect (30-50%) of superoxide dismutase, by the reaction stoichiometry, and by the enzyme turnover numbers for NADH and Cu(II). The cupric reductase activity of NDH-2 was dependent on thiol groups which were accessible to p-chloromercuribenzoate at low, but not at high, ionic strength of the medium, a fact apparently connected to a conformational change of the protein. To our knowledge, this is the first protein with cupric reductase activity to be isolated and characterized in its biochemical properties.

Binding Sites↗
PubMed1997

Specific localization of the respiratory alternative oxidase in meristematic and xylematic tissues from developing soybean roots and hypocotyls.

We used tissue printing and specific immunostaining to examine the localization of the alternative oxidase (AOX) protein in correlation with measurements of AOX capacity. Selected root and hypocotyl regions were analyzed during the first 14 d of growth. It is shown that AOX protein is localized in the apical meristem and in developing xylem. The temporal pattern of expression is coincident with the evolution of AOX capacity. Data suggest that AOX expression is linked to xylem differentiation. Since heat is a major product of the alternative pathway, we speculate that thermogenesis is implicated in morphogenesis.

Gene Expression Regulation, Developmental↗
PubMed1995

Sites of electron transfer to membrane-bound copper and hydroperoxide-induced damage in the respiratory chain of Escherichia coli.

Previous studies in Escherichia coli as a model system for peroxide toxicity (L. Rodríguez-Montelongo, L. C. De la Cruz-Rodríguez, R. N. Farías, and E. M. Massa, 1993, Biochim. Biophys. Acta 1144, 77-84) have shown that electron flow through the respiratory chain supports a membrane-associated Cu(II)/Cu(I) redox cycle involved in irreversible impairment of the respiratory system by tert-butyl hydroperoxide (t-BOOH). In this paper, E. coli mutants deficient in specific respiratory chain components have been used to determine the sites of copper reduction and the targets inactivated by t-BOOH. Two sites of electron transfer to membrane-bound copper were identified: one in the region between NADH and ubiquinone supported by NADH as electron donor and another localized between ubiquinone and the cytochromes supported by electrons coming from NADH, succinate, or D-lactate. Electron flow through the former site in the presence of t-BOOH led to inactivation of NADH dehydrogenase II, whereas electron flow through the latter site in the presence of the hydroperoxide led to damage of ubiquinone. In agreement with the above in vitro results with isolated membranes, copper-dependent inactivation of NADH dehydrogenase and ubiquinone was demonstrated in E. coli cells exposed to t-BOOH. It is proposed that the t-BOOH-induced damage is a consequence of t-butylalkoxy radical generation through a Fenton-type reaction mediated by redox cycling of membrane-bound copper at those two loci of the respiratory chain.

Cell Membrane↗
PubMed1993

Membrane-associated redox cycling of copper mediates hydroperoxide toxicity in Escherichia coli.

We are studying the action of tert-butylhydroperoxide (t-BOOH) on Escherichia coli as a model system for peroxide toxicity. In our previous report (De la Cruz-Rodriguez, L.C., Farías, R.N. and Massa, E.M. (1990) Biochim. Biophys. Acta 1015, 510-516), the respiratory chain was identified as a major target of t-BOOH. In the present paper, we study further the effect of t-BOOH on the NADH oxidase of the E. coli respiratory chain to clarify the mechanism of damage, especially regarding the identity and role of the metal ion involved. The results are: (a) t-BOOH toxicity is mediated by membrane-bound copper ions; (b) a small pool of the membrane-bound copper is reduced from Cu(II) to Cu(I) in the presence of NADH and other respiratory substrates (succinate, D-lactate); (c) this reduction of copper occurs at 37 degrees C but not at 0 degrees C or when the membranes are inactivated by previous heating; (d) the Cu(I) generated by reduction of Cu(II) during membrane preincubation with NADH, is oxidized by t-BOOH with simultaneous inactivation of the NADH oxidase, whereas treatment with only t-BOOH (without NADH) has no effect on the oxidase. It is concluded that the effect of t-BOOH on the respiratory chain is mediated by redox cycling of copper. It is proposed that the damage results from activation of the hydroperoxide through its interaction with Cu(I) in a site-specific Fenton-type reaction.

Cell Membrane↗
PubMed1993

Alkoxyl and methyl radical formation during cleavage of tert-butyl hydroperoxide by a mitochondrial membrane-bound, redox active copper pool: an EPR study.

The cleavage of tert-butyl hydroperoxide by submitochondrial particles yielded two distinctive radicals, alkoxyl and methyl radicals, detected by the electron paramagnetic resonance technique in conjunction with the spin trap 5,5'-dimethyl-1-pyrrolyne-N-oxide. Free radical formation was partly sensitive to bathocuproine disulfonate and was augmented upon supplementation of the mitochondrial membranes with copper, thus suggesting that a redox active copper pool in mitochondrial membranes participated actively in the cleavage of the O-O bond of tert-butyl hydroperoxide. This view was experimentally substantiated by the following: first, observation of the maximal EPR signal intensity required the presence of exogenous electron donors, such as succinate or reduced nicotinamide adenine dinucleotide (NADH). Second, copper reduction was accomplished partly by a superoxide radical-dependent mechanism as indicated by the sensitivity of the electron paramagnetic resonance (EPR) signal to superoxide dismutase. Third, the enhancing effect of the respiratory chain inhibitors, antimycin A and rotenone, on free radical yield assessed in the presence of superoxide dismutase pointed to the occurrence of two potential loci in the respiratory chain involved in direct electron transfer to membrane-bound copper: one located between NADH and the rotenone-sensitive site and another, quantitatively less important, between the rotenone- and antimycin-sensitive sites. These results support the notion that a redox pool of copper tightly bound to the mitochondrial membrane contributes significantly to the reductive cleavage of organic peroxides associated with free radical production.

Animals↗
PubMed1993

Starved cells of the fatty acid auxotroph Escherichia coli AK7 develop abnormal sensitivity to media with low osmolarity.

The unsaturated fatty acid auxotroph Escherichia coli AK7 supplied with linolenic acid, while appearing normal during logarithmic growth, showed a fast decline in CFU during starvation as a result of an osmotic downshift when transferred to standard agar plates unsupplemented with an osmolyte such as 300 mosM sucrose or salt (NaCl or KCl). The starved cells could recover their osmoresistance when an energy source was added to the starvation medium.

Culture Media↗
PubMed1990

Damage of Escherichia coli cells by t-butylhydroperoxide involves the respiratory chain but is independent of the presence of oxygen.

The action of t-butylhydroperoxide (tBOOH) on Escherichia coli cells has been studied as a model system for organic peroxide toxicity. Exposure of E. coli cells to tBOOH led to progressive and irreversible impairment of the respiratory function, an effect which was dependent on the availability of substrate. The effect of tBOOH on growth of E. coli with different carbon sources and alternative terminal electron acceptors was investigated. It was found that the sensitivity of E. coli to tBOOH under diverse growth conditions implicating a functional respiratory chain was greater than when the bacterium grew by fermentation. Also the mutant E. coli SASX76, which requires exogenous 5-aminolevulinic acid to synthesize the cytochromes, was more resistant to tBOOH when lacking a functional respiratory chain. These data point to the respiratory chain as a major target in the in vivo action of tBOOH. Experiments with isolated membranes also showed a tBOOH-induced damage of the respiratory chain monitored by impairment of the NADH oxidase. The effect of tBOOH was produced even under anaerobiosis, indicating that development of cell damage was independent of oxygen and, therefore, that neither oxygen-derived radicals nor lipid peroxidation were involved.

Cell Membrane↗
PubMed1988

Influence of unsaturated fatty acid membrane component on sensitivity of an Escherichia coli fatty acid auxotroph to conditions of nutrient depletion.

The unsaturated fatty acid auxotroph Escherichia coli AK7 was provided with either oleic acid (cis 18:1) or linolenic acid (cis 18:3) to vary the degree of unsaturation of cell membrane lipids. The susceptibility of oleic acid- and linolenic acid-grown cells to starvation at 37 degrees C in 154 mM NaCl was compared following the decline in the number of CFU by plating the cells on agar medium. The decline in CFU was faster for linolenic acid-than for oleic acid-grown cells, but it was not indicative of cell death, since culturable CFU was recovered after respirable substrate was added to the starved cell suspension. Cell envelope microviscosity (determined by fluorescence polarization) of oleic acid- and linolenic acid-grown cells was equal in the presence of a respirable substrate, but in its absence the microviscosity of linolenic acid-grown cells was lower than that of oleic acid-grown cells. The results suggest that cell envelope microviscosity is an important factor in determining the sensitivity of E. coli to conditions of nutrient depletion.

Cell Membrane↗
PubMed1985

Study of a time lag in the assay of Escherichia coli membrane-bound dehydrogenases based on tetrazolium salt reduction.

The Escherichia coli membrane-bound D-lactate dehydrogenase and succinate dehydrogenase were assayed on the basis of the phenazine methosulfate- (PMS-) mediated reduction of the tetrazolium salt, MTT. An initial slower phase (lag) in the time-course of the reaction was observed and analyzed. The results were as follows. (1) The time lag in the assay of the D-lactate dehydrogenase was eliminated by preincubating the membranes with PMS plus D-lactate, with PMS plus succinate, or with PMS plus NADH (conditions which implicated PMS reduction). (2) When the D-lactate dehydrogenase was assayed by another method based on the measurement of the pyruvate formed, neither was a time lag observed nor was the enzyme activity affected by membrane preincubation with PMS plus D-lactate. (3) Although the superoxide radical was involved in MTT reduction, this radical seemed not to participate in the generation of the time lag. (4) Membranes whose D-lactate dehydrogenase activity had previously been destroyed by heating at 80 degrees C for 1 min, were able to prolong the time lag in MTT reduction when added to the assay medium for the D-lactate dehydrogenase from untreated membranes, whereas membranes previously heated at 100 degrees C instead of 80 degrees C did not have this effect. It was concluded that the E. coli membranes interfered in the dehydrogenase assay based on the PMS-mediated reduction of MTT. The time lag was interpreted as a period during which the interfering substance reacted with reduced PMS inhibiting the reduction of MTT.

Escherichia coli↗
PubMed1983

Effect of auto-oxidized phospholipids on oxidative enzyme assays based on tetrazolium salt reduction.

The influence of auto-oxidized phospholipids on the reduction of the tetrazolium salt MTT coupled to the NAD+-dependent lactate dehydrogenase reaction was studied. The following results were obtained: (1) peroxidized phosphatidylcholine interfered in the time-course of the lactate dehydrogenase-mediated MTT reduction; (2) there was a time-dependent decrease in the hydroperoxide content of phosphatidylcholine vesicles during the incubation; (3) the diminution of phosphatidylcholine hydroperoxides required the presence of all the components of the system except MTT; (4) hydroperoxide diminution and MTT reduction were mediated by the superoxide radical O2-, since both processes were inhibited by superoxide dismutase; (5) EDTA inhibited the hydroperoxide decrease and abolished the interference of peroxidized phosphatidylcholine with MTT reduction. It was concluded that hydroperoxides compete with MTT for the electrons coming from substrate oxidation. The superoxide radical O2- and traces of some contaminating metal ion are involved in the process. This is a potential complication in the study of the effect of lipids on enzymatic activities assayed by the tetrazolium salt method.

Edetic Acid↗
PubMed1976

Differentiation of cholesterol compartments in the immature chick testis.

The behaviour of testicular free and esterified cholesterol during early posthatching development and after stimulation with human chorionic gonadotrophin was studied in the immature chick using combined electron microscope and biochemical techniques. The interstitial cells represented about 65% of the testicular tissue and the lipid droplets in the cytoplasm of these cells were considerably depleted after HCG treatment. The lipid droplets isolated from 7-day-old testis contained about 95% of the total esterified cholesterol which was significantly reduced in the testis and isolated lipid droplets after HCG stimulation. The bulk of free cholesterol was associated with the microsomal fraction whose membranes and cholesterol content increased during normal maturation and after gonadotrophin-induced differentiation.

Animals↗
PubMed1975

Subcellular compartmentation of free and esterified cholesterol in the interstitial cells of the mouse testis.

The subcellular distribution of free and esterified cholesterol in mouse testis and the changes occurring in cholesterol content of whole testes and cell fractions after inhibition of gonadotropins with methallibure (ICI 33, 828) and restimulation with human chorionic gonadotropin (HCG) are reported in the present paper. In subcellular fractions, the bulk of free cholesterol is associated with organelles sedimented in the microsomal fraction while esterified cholesterol is mainly stored in isolated lipid droplets. The latter compartment increases in methallibure-treated mice 2.3 fold and is remarkably depleted after administration of HCG. There is a close parallelism between the changes in esterified cholesterol content and the variation in the numbers of lipid droplets found in electron micrographs of interstitial cells of mice receiving similar treatments. By contrast no significant changes were noticed in either free cholesterol concentrations of the microsomal fractions or in the fine structure of organelles associated with this fraction. The dynamic nature of steroidogenesis in the microsomal fraction requires the existence of a free cholesterol pool with a high turnover rate for use as an intermediate in androgen synthesis. On the other hand, the large content of free cholesterol in microsomes and its stability under different conditions suggest the presence of a cholesterol compartment with a slow turnover, as a constituent of the membranes.

Animals↗