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J B Hughes

Publications and source records attributed to J B Hughes.

30 records · Page 2Linked to original sources
PubMed1984

Evidence for the involvement of coupling factor B in the H+ channel of the mitochondrial H+-ATPase.

Membrane energization by ATP has been measured in vesicles containing purified bovine heart mitochondrial H+-ATPase (ATP synthase) with the voltage-sensitive dye oxonol VI. The dithiol chelator, Cd2+, and the thiol oxidant, copper o-phenanthroline, produced discharge of the membrane potential when added at the steady state and inhibited its establishment when added prior to energization by ATP. These effects, which were reversed by dithiothreitol, were not accompanied by an increase in the nonspecific H+ permeability of the membrane. Passive H+ conduction in proteoliposomes containing F0 (hydrophobic segment of ATP synthase) was assayed by the quenching of 9-aminoacridine fluorescence after establishing a K+ diffusion potential. This conductance was blocked by Cd2+, an inhibitor of coupling factor B (FB). Labeling of F0 with 115Cd2+ at the concentrations that inhibited the F0 conductance followed by gel electrophoresis yielded a single radioactive band with a molecular weight corresponding to FB, the presence of which in the F0 preparation was confirmed by immunoblot staining. The data offer strong evidence that FB is an essential component of the H+ channel of F0, because H+ conduction through the channel is inhibited by chemical modification of FB.

Adenosine Triphosphatases↗
PubMed1982

On the role of factor B and oligomycin on generation and discharge of the proton gradient.

Bovine mitochondrial coupling factor B (FB) stimulates oxidative phosphorylation as well as other energy-linked reactions which are supported by ATP hydrolysis. Extraction of FB from submitochondrial particles results in a decrease in ATP-dependent proton translocation (delta pH) and binding of the voltage-sensitive dye, oxonol VI. Reconstitution of deficient particles with FB restores ATP-dependent proton translocation and oxonol binding but has little effect on oxonol binding supported by respiratory substrates.l In contrast, low levels of oligomycin stimulate oxonol binding supported by either ATP or NADH. In the case of oligomycin, the stimulatory effect is associated with a decrease in the rate of discharge of the proton gradient, but the depletion of FB or its restoration has no detectable effect on the discharge rate. The data indicate that the primary effect of FB is upon the rate of H+ translocation coupled to ATP hydrolysis, while that of low oligomycin is on the H+ permeability of the membrane.

Animals↗
PubMed1981

Inhibition of coupling factor B activity by cadmium ion, arsenite-2,3-dimercaptopropanol, and phenylarsine oxide, and preferential reactivation by dithiols.

Coupling factor B activity was measured by the stimulation of the ATP-driven NAD+ reduction by succinate or the 32Pi-ATP exchange activity of Factor B-depleted submitochondrial particles. Half-maximal coupling activity was inhibited by 30 microM cadmium, 5 microM phenylarsine oxide, or 0.3 mM arsenite-2,3-dimercaptopropanol. The inhibition was relieved by slight excess of dithiol but not by a 10-fold molar excess of 2-mercaptoethanol. Inhibition of coupling activity by phenylarsine oxide or cadmium was not due to interference in binding of Factor B to depleted particles. Isolated Factor B binds phenylarsine oxide resulting in loss of ability to stimulate depleted submitochondrial particles. The inhibition was largely overcome by dithiol but not by monothiols. The residual coupling activity of depleted submitochondrial particles was highly resistant to cadmium or arsenical. Moreover, binding of arsenical to the depleted particles per se, did not result in inhibition of Factor B-stimulated activity. Furthermore, the addition of phenylarsine oxide to H+-ATPase resulted in loss of Pi-ATP exchange and stimulation of oligomycin-sensitive ATPase activities. Both effects were further potentiated by 2-mercaptoethanol and reversed by dithiols. These effects parallel uncoupling of oxidative phosphorylation in mitochondria by these inhibitors and point to Factor B as the probable component sensitive to these inhibitors.

Adenosine Triphosphatases↗
PubMed1981

Occurrence of proteins immunoreactive with anti-coupling factor B in phosphorylating membrane preparations.

Coupling factor B has been isolated from beef heart mitochondria, apparently in multiple forms which differ in molecular weight and specific activity. Since it has no known intrinsic catalytic activity, detection and quantitation have been based upon the factor B-dependent stimulation of ATP-linked activities in factor B-deficient sub-mitochondrial particles. This communication reports the development of a reliable and more universally applicable enzyme-linked immunosorbent assay (ELISA) for detection and quantitation of factor B in soluble or membranous preparations. The assay requires nanoliter volumes of rabbit antiserum raised against purified factor B and will detect nanogram amounts of the coupling factor. Analysis of beef heart submitochondrial particles using a competitive binding ELISA indicated a factor B content of 0.27 nmol/mg protein, making factor B stoichiometric with F1 (0.3--0.6 nmol/mg). Furthermore, application of the factor B ELISA has indicated the presence of material cross-reacting with the beef heart factor B-antiserum in phosphorylating membranes from chloroplasts, Escherichia coli, Paracoccus denitrificans and the thermophilic bacterium, PS3. Negative results were obtained with mitochondria and microsomes from rat liver, purple membranes from Halobium halobacterium and sarcoplasmic reticulum from rabbit skeletal muscle.

Animals↗
PubMed1981

Activation of potassium-dependent H+ efflux from mitochondria by cadmium and phenylarsine oxide.

Addition of Cd2+ or phenylarsine oxide (PhAsO) to respiring rat liver mitochondria results first in acidification of the medium (H+ efflux) followed by disappearance of H+ (discharge of the pH gradient or uncoupling). The first phase of H+ efflux is dependent upon the presence of K+ in the medium, and is not seen in the presence of valinomycin, which is consistent with the conclusion that H+ efflux is linked to membrane potential-dependent uptake of K+. These effects are abolished by low levels of 2,3-dimercaptopropanol but potentiated by excess of 2-mercaptoethanol, showing involvement of a dithiol type of group in the response. Mersalyl produces only the H+ efflux, and subsequent addition of Cd2+ of PhAsO produces collapse of the delta pH.

Animals↗
PubMed1976

Therapy with gastrin antibody in the Zollinger-Ellison syndrome.

The therapeutic effectiveness of parenterally administered rabbit antigastrin antibody was evaluated in a patient with the Zollinger-Ellison syndrome who had a fasting serum gastrin level of 3020 pg/ml and a basal gastric acid secretion of 48.9 mEq/hr. Control globulin reduced gastric secretion to 32 mEq/hr. Gastrin antibody reduced it futher to 8.7 mEq/hr. Betazole hydrochloride which was given 75 min after administration of gastrin antibody stimulated acid secretion to 57.2 mEq/hr. One day later basal acid secretion was uninhibited although some antibody activity was present in the patient's serum. The results suggested that gastrin antibody acutely inhibited basal but not betazole-stimulated secretion.

Adult↗
PubMedDate not supplied

Utilization of bioremediation processes for the treatment of PAH-contaminated sediments.

The widespread contamination of aquatic sediments by polycyclic aromatic hydrocarbons (PAHs) has created a need for cost-effective remediation processes. Many common PAHs are biodegradable, leading to studies investigating the potential of sediment bioremediation. This article reviews several factors that currently complicate the implementation of sediment bioremediation processes: the effect of complex mixtures of contaminants on the rate and extent of degradation observed, the bioavailability of PAHs in sorbed- and nonaqueous-phase, and methods being evaluated to enhance degradation/availability (surfactant-enhanced solubility, nutrient addition, and bioaugmentation).

Bacteria↗