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114 results on '"Gardner, Paul R."'

31. Pseudomonas aeruginosa Anaerobic Respiration in Biofilms

Author

Yoon, Sang Sun, primary, Hennigan, Robert F., additional, Hilliard, George M., additional, Ochsner, Urs A., additional, Parvatiyar, Kislay, additional, Kamani, Moneesha C., additional, Allen, Holly L., additional, DeKievit, Teresa R., additional, Gardner, Paul R., additional, Schwab, Ute, additional, Rowe, John J., additional, Iglewski, Barbara H., additional, McDermott, Timothy R., additional, Mason, Ronald P., additional, Wozniak, Daniel J., additional, Hancock, Robert E.W., additional, Parsek, Matthew R., additional, Noah, Terry L., additional, Boucher, Richard C., additional, and Hassett, Daniel J., additional

Published
2002
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34. Dioxygen-Dependent Metabolism of Nitric Oxide.

Author

Walker, John M., Hassid, Aviv, Gardner, Paul R., Gardner, Anne M., and Hallstrom, Craig K.

Abstract

Nitric oxide (NO) serves critical signaling, energetic, and toxic functions throughout the biosphere. NO steady-state levels and functions are controlled in part by NO metabolism or degradation. Dioxygen-dependent NO dioxygenases (EC 1.14.12.17) and dioxygen-independent NO reductases (EC 1.7.99.7) are being identified as major routes for NO metabolism in various life forms. Here we describe the use of the Clark-type NO electrode, mechanistic inhibitors, and nitrate/nitrite assays to measure, characterize, and identify major NO metabolic pathways and enzymes in bacteria, fungi, plants, mammalian cells, and organelles. The methods may prove to be particularly useful for mechanistic investigations and the development of inhibitors, inducers, and other novel NO-modulating therapeutics. [ABSTRACT FROM AUTHOR]

Published
2004
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48. Steady-state and Transient Kinetics of Escherichia coliNitric-oxide Dioxygenase (Flavohemoglobin)

Author

Gardner, Anne M., Martin, Lori A., and Gardner, Paul R.

Abstract

Escherichia coliexpresses an inducible flavohemoglobin possessing robust NO dioxygenase activity. At 37 °C, the enzyme shows a maximal turnover number (Vmax) of 670 s−1andKmvalues for NADH, NO, and O2equal to 4.8, 0.28, and ∼100 μm, respectively. Individual reduction, ligand binding, and NO dioxygenation reactions were examined at 20 °C, where Vmaxis ∼94 s−1. Reduction by NADH occurs in two steps. NADH reduces bound FAD with a rate constant of ∼15 μm−1s−1, and heme iron is reduced by FADH2with a rate constant of 150 s−1. Dioxygen binds tightly to reduced flavohemoglobin, with association and dissociation rate constants equal to 38 μm−1s−1and 0.44 s−1, respectively, and the oxygenated flavohemoglobin dioxygenates NO to form nitrate. NO also binds reversibly to reduced flavohemoglobin in competition with O2, dissociates slowly, and inhibits NO dioxygenase activity at [NO]/[O2] ratios of 1:100. Replacement of the heme pocket B10 tyrosine with phenylalanine increases the O2dissociation rate constant ∼80-fold and reduces NO dioxygenase activity ∼30-fold, demonstrating the importance of the tyrosine hydroxyl for O2affinity and NO scavenging activity. At 37 °C,Vmax/Km(NO) is 2,400 μm−1s−1, demonstrating that the enzyme is extremely efficient at converting toxic NO into nitrate under physiological conditions.

Published
2000
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49. Pseudomonas aeruginosa Anaerobic Respiration in Biofilms Relationships to Cystic Fibrosis Pathogenesis

Author

Yoon, Sang Sun, Hennigan, Robert F., Hilliard, George M., Ochsner, Urs A., Parvatiyar, Kislay, Kamani, Moneesha C., Allen, Holly L., DeKievit, Teresa R., Gardner, Paul R., Schwab, Ute, Rowe, John J., Iglewski, Barbara H., McDermott, Timothy R., Mason, Ronald P., Wozniak, Daniel J., Hancock, Robert E.W., Parsek, Matthew R., Noah, Terry L., Boucher, Richard C., and Hassett, Daniel J.

Subjects
biochemical phenomena, metabolism, and nutrition
Abstract

Recent data indicate that cystic fibrosis (CF) airway mucus is anaerobic. This suggests that Pseudomonas aeruginosa infection in CF reflects biofilm formation and persistence in an anaerobic environment. P. aeruginosa formed robust anaerobic biofilms, the viability of which requires rhl quorum sensing and nitric oxide (NO) reductase to modulate or prevent accumulation of toxic NO, a byproduct of anaerobic respiration. Proteomic analyses identified an outer membrane protein, OprF, that was upregulated ∼40-fold under anaerobic versus aerobic conditions. Further, OprF exists in CF mucus, and CF patients raise antisera to OprF. An oprF mutant formed poor anaerobic biofilms, due, in part, to defects in anaerobic respiration. Thus, future investigations of CF pathogenesis and therapy should include a better understanding of anaerobic metabolism and biofilm development by P. aeruginosa.

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