scholarly journals Structure of heme d 1-free cd 1 nitrite reductase NirS

2020 ◽  
Vol 76 (6) ◽  
pp. 250-256
Author(s):  
Thomas Klünemann ◽  
Wulf Blankenfeldt
Keyword(s):  
Nitric Oxide ◽  
Pseudomonas Aeruginosa ◽  
Nitrite Reductase ◽  
Active Site ◽  
Opportunistic Pathogen ◽  
Active Enzyme ◽  
Free Form ◽  
Nitrate Respiration ◽  
Gram Negative ◽  
Open Conformation

A key step in anaerobic nitrate respiration is the reduction of nitrite to nitric oxide, which is catalysed by the cd 1 nitrite reductase NirS in, for example, the Gram-negative opportunistic pathogen Pseudomonas aeruginosa. Each subunit of this homodimeric enzyme consists of a cytochrome c domain and an eight-bladed β-propeller that binds the uncommon isobacteriochlorin heme d 1 as an essential part of its active site. Although NirS has been well studied mechanistically and structurally, the focus of previous studies has been on the active heme d 1-bound form. The heme d 1-free form of NirS reported here, which represents a premature state of the reductase, adopts an open conformation with the cytochrome c domains moved away from each other with respect to the active enzyme. Further, the movement of a loop around Trp498 seems to be related to a widening of the propeller, allowing easier access to the heme d 1-binding side. Finally, a possible link between the open conformation of NirS and flagella formation in P. aeruginosa is discussed.

scholarly journals Structure of heme d1-free cd1 nitrite reductase NirS

2020 ◽  
Author(s):  
Thomas Klünemann ◽  
Wulf Blankenfeldt
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Nitrite Reductase ◽  
Active Site ◽  
Opportunistic Pathogen ◽  
Free Form ◽  
Nitrate Respiration ◽  
Gram Negative ◽  
Open Conformation ◽  
Heme D1 ◽  
Insight Into

AbstractA key step in anaerobic nitrate respiration is the reduction of nitrite to nitric oxide, which is catalysed by cd1 nitrite reductase NirS in e.g. the gram-negative opportunistic pathogen Pseudomonas aeruginosa. Each subunit of this homodimeric enzyme consists of a cytochrome c domain and an eight-bladed β-propeller that binds the uncommon isobacteriochlorin heme d1 as an essential part of its active site. Although NirS is mechanistically and structurally well studied, the focus of previous studies has been on the active, heme d1-bound form. The heme d1-free form of NirS reported here, representing a premature state of the reductase, adopts an open conformation with the cytochrome c domains moved away from each other with respect to the active enzyme. Further, movement of a loop around W498 seems to be related to a widening of the propeller, allowing easier access to the heme d1 binding side. Finally, a possible link between the open conformation of NirS and flagella formation in P. aeruginosa is discussed.SynopsisThe crystal structure of heme d1-free cd1 nitrite reductase NirS from Pseudomonas aeruginosa has been determined and provides insight into a premature form of the enzyme.

New insights into the activity of Pseudomonas aeruginosa cd1 nitrite reductase

2008 ◽  
Vol 36 (6) ◽  
pp. 1155-1159 ◽  
Author(s):  
Serena Rinaldo ◽  
Alessandro Arcovito ◽  
Giorgio Giardina ◽  
Nicoletta Castiglione ◽  
Maurizio Brunori ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Pseudomonas Aeruginosa ◽  
Nitrite Reductase ◽  
Nitrite Reduction ◽  
Nitrite Reductases ◽  
Cytochrome Cd1 ◽  
Haem Iron ◽  
Shed Light ◽  
Denitrification Process

The cytochrome cd1 nitrite reductases are enzymes that catalyse the reduction of nitrite to nitric oxide (NO) in the bacterial energy conversion denitrification process. These enzymes contain two different redox centres: one covalently bound c-haem, which is reduced by external donors, and one peculiar d1-haem, where catalysis occurs. In the present paper, we summarize the current understanding of the reaction of nitrite reduction in the light of the most recent results on the enzyme from Pseudomonas aeruginosa and discuss the differences between enzymes from different organisms. We have evidence that release of NO from the ferrous d1-haem occurs rapidly enough to be fully compatible with the turnover, in contrast with previous hypotheses, and that the substrate nitrite is able to displace NO from the d1-haem iron. These results shed light on the mechanistic details of the activity of cd1 nitrite reductases and on the biological role of the d1-haem, whose presence in this class of enzymes has to date been unexplained.

scholarly journals Involvement of Nitric Oxide in Biofilm Dispersal of Pseudomonas aeruginosa

2006 ◽  
Vol 188 (21) ◽  
pp. 7344-7353 ◽  
Author(s):  
Nicolas Barraud ◽  
Daniel J. Hassett ◽  
Sung-Hei Hwang ◽  
Scott A. Rice ◽  
Staffan Kjelleberg ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Pseudomonas Aeruginosa ◽  
Antimicrobial Agents ◽  
Nitrosative Stress ◽  
Sodium Dodecyl ◽  
Anaerobic Respiration ◽  
Opportunistic Pathogen ◽  
No Donor ◽  
Biofilm Dispersal ◽  
Novel Strategy

ABSTRACT Bacterial biofilms at times undergo regulated and coordinated dispersal events where sessile biofilm cells convert to free-swimming, planktonic bacteria. In the opportunistic pathogen Pseudomonas aeruginosa, we previously observed that dispersal occurs concurrently with three interrelated processes within mature biofilms: (i) production of oxidative or nitrosative stress-inducing molecules inside biofilm structures, (ii) bacteriophage induction, and (iii) cell lysis. Here we examine whether specific reactive oxygen or nitrogen intermediates play a role in cell dispersal from P. aeruginosa biofilms. We demonstrate the involvement of anaerobic respiration processes in P. aeruginosa biofilm dispersal and show that nitric oxide (NO), used widely as a signaling molecule in biological systems, causes dispersal of P. aeruginosa biofilm bacteria. Dispersal was induced with low, sublethal concentrations (25 to 500 nM) of the NO donor sodium nitroprusside (SNP). Moreover, a P. aeruginosa mutant lacking the only enzyme capable of generating metabolic NO through anaerobic respiration (nitrite reductase, ΔnirS) did not disperse, whereas a NO reductase mutant (ΔnorCB) exhibited greatly enhanced dispersal. Strategies to induce biofilm dispersal are of interest due to their potential to prevent biofilms and biofilm-related infections. We observed that exposure to SNP (500 nM) greatly enhanced the efficacy of antimicrobial compounds (tobramycin, hydrogen peroxide, and sodium dodecyl sulfate) in the removal of established P. aeruginosa biofilms from a glass surface. Combined exposure to both NO and antimicrobial agents may therefore offer a novel strategy to control preestablished, persistent P. aeruginosa biofilms and biofilm-related infections.

The Pseudomonas aeruginosa DNR transcription factor: light and shade of nitric oxide-sensing mechanisms

2011 ◽  
Vol 39 (1) ◽  
pp. 294-298 ◽  
Author(s):  
Giorgio Giardina ◽  
Nicoletta Castiglione ◽  
Manuela Caruso ◽  
Francesca Cutruzzolà ◽  
Serena Rinaldo
Keyword(s):  
Nitric Oxide ◽  
Pseudomonas Aeruginosa ◽  
Regulatory Protein ◽  
Structural Data ◽  
Activation Mechanism ◽  
Receptor Protein ◽  
Nitrate Respiration ◽  
Global Changes ◽  
Low Oxygen ◽  
Haem Protein

In response to environmental conditions, NO (nitric oxide) induces global changes in the cellular metabolism of Pseudomonas aeruginosa, which are strictly related to pathogenesis. In particular, at low oxygen tensions and in the presence of NO the denitrification alternative respiration is activated by a key regulator: DNR (dissimilative nitrate respiration regulator). DNR belongs to the CRP (cAMP receptor protein)–FNR (fumarate and nitrate reductase regulatory protein) superfamily of bacterial transcription factors. These regulators are involved in many different pathways and distinct activation mechanism seems to be operative in several cases. Recent results indicate that DNR is a haem protein capable of discriminating between NO and CO (carbon monoxide). On the basis of the available structural data, a suggested activation mechanism is discussed.

scholarly journals Identification of OprF as a Complement Component C3 Binding Acceptor Molecule on the Surface of Pseudomonas aeruginosa

2015 ◽  
Vol 83 (8) ◽  
pp. 3006-3014 ◽  
Author(s):  
Meenu Mishra ◽  
Adam Ressler ◽  
Larry S. Schlesinger ◽  
Daniel J. Wozniak
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Opportunistic Pathogen ◽  
Gram Negative Bacteria ◽  
Acceptor Molecule ◽  
Wild Type ◽  
Gram Negative ◽  
Content Type ◽  
Persistent Infections ◽  
Structural Identity ◽  
Complement Component C3

Pseudomonas aeruginosais a versatile opportunistic pathogen that can cause devastating persistent infections. Complement is a highly conserved pathway of the innate immune system, and its role in the first line of defense against pathogens is widely appreciated. One of the earliest events in the complement cascade is the conversion of C3 to C3a and C3b, the latter typically binds to one or more acceptor molecules on the pathogen surface. We previously demonstrated that complement C3b binding acceptors exist on theP. aeruginosasurface. In the current study, we utilized either C3 polyclonal or C3b monoclonal antibodies in a far-Western technique followed by mass spectroscopy to identify the C3b acceptor molecule(s) on theP. aeruginosasurface. Our data provide evidence that OprF (an outer membrane porin, highly conserved in thePseudomonadaceae) binds C3b. AnoprF-deficientP. aeruginosastrain exhibits reduced C3 deposition compared to the wild type. We observed reduced internalization ofoprF-deficient bacteria by neutrophils after opsonization compared with wild-typeP. aeruginosa. Heterologous expression of OprF significantly enhanced C3b binding and increased serum-mediated bactericidal effects in complement-susceptibleEscherichia coli. Furthermore, the predicted secondary structure of the C-terminal, surface-exposed region of OprF has high structural identity to the OmpA domain of several other Gram-negative bacteria, one of which is known to bind C3b. Therefore, these findings provide new insights into the biology of complement interactions withP. aeruginosaand other Gram-negative bacteria.

Exploration of the Pharmacodynamics for Pseudomonas aeruginosa Biofilm Eradication by Tobramycin

2021 ◽  
Author(s):  
Devin Sindeldecker ◽  
Shaurya Prakash ◽  
Paul Stoodley
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Drug Resistance ◽  
Treatment Duration ◽  
Area Under The Curve ◽  
Opportunistic Pathogen ◽  
Multi Drug Resistance ◽  
Antibiotic Concentration ◽  
Antibiotic Resistant ◽  
Gram Negative

Pseudomonas aeruginosa is a Gram-negative, opportunistic pathogen which is involved in numerous infections. It is of growing concern within the field of antibiotic resistant and tolerance and often exhibits multi-drug resistance. Previous studies have shown the emergence of antibiotic resistant and tolerant variants within the zone of clearance of a biofilm lawn after exposure to aminoglycosides. As concerning as the tolerant variant emergence is, there was also a zone of killing (ZOK) immediately surrounding the antibiotic source from which no detectable bacteria emerged or were cultured. In this study, the ZOK was analyzed using both in vitro and in silico methods to determine if there was a consistent antibiotic concentration versus time constraint (area under the curve, (AUC)) which is able to completely kill all bacteria in the lawn biofilms in our in vitro model. Our studies revealed that by achieving an average AUC of 4,372.5 μg*hr/mL, complete eradication of biofilms grown on both agar and hydroxyapatite was possible. These findings show that appropriate antibiotic concentrations and treatment duration may be able to treat antibiotic resistant and tolerant biofilm infections.

Pseudomonas aeruginosa

2020 ◽  
pp. 1041-1044
Author(s):  
G.C.K.W. Koh ◽  
Sharon J. Peacock
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Urinary Tract ◽  
Opportunistic Pathogen ◽  
Selective Advantage ◽  
Innocent Bystander ◽  
Negative Bacterium ◽  
Gram Negative ◽  
Skin Ulcers ◽  
Wide Range ◽  
Pathogen Diagnosis

Pseudomonas aeruginosa is a highly versatile environmental Gram-negative bacterium that can be isolated from a wide range of habitats, including soil, marshes, and the ocean, as well as from plant and animal tissues. It is resistant to many disinfectants and antibiotics, giving it a selective advantage in hospitals. It rarely causes infection in the healthy host but is a major opportunistic pathogen. Diagnosis is usually straightforward when the organism is cultured from samples collected from normally sterile sites, but is often challenging when infection is suspected in non-sterile sites such as a catheterized urinary tract, burns, or skin ulcers, because P. aeruginosa may be either a pathogen or an innocent bystander. Treatment can be challenging as P. aeruginosa is intrinsically resistant to a broad range of antimicrobials.

The catalytic mechanism of Pseudomonas aeruginosa cd1 nitrite reductase

2011 ◽  
Vol 39 (1) ◽  
pp. 195-200 ◽  
Author(s):  
Serena Rinaldo ◽  
Giorgio Giardina ◽  
Nicoletta Castiglione ◽  
Valentina Stelitano ◽  
Francesca Cutruzzolà
Keyword(s):  
Nitric Oxide ◽  
Pseudomonas Aeruginosa ◽  
Active Site ◽  
Catalytic Mechanism ◽  
Product Inhibition ◽  
Electron Donors ◽  
Nitrite Reduction ◽  
Nitrite Reductases ◽  
Shed Light ◽  
Denitrification Process

The cd1 NiRs (nitrite reductases) are enzymes catalysing the reduction of nitrite to NO (nitric oxide) in the bacterial energy conversion denitrification process. These enzymes contain two distinct redox centres: one covalently bound c-haem, which is reduced by external electron donors, and another peculiar porphyrin, the d1-haem (3,8-dioxo-17-acrylate-porphyrindione), where nitrite is reduced to NO. In the present paper, we summarize the most recent results on the mechanism of nitrite reduction by the cd1 NiR from Pseudomonas aeruginosa. We discuss the essential catalytic features of this enzyme, with special attention to the allosteric regulation of the enzyme's activity and to the mechanism employed to avoid product inhibition, i.e. trapping of the active-site reduced haem by the product NO. These results shed light on the reactivity of cd1 NiRs and assign a central role to the unique d1-haem, present only in this class of enzymes.

scholarly journals ELIMINATION OF PSEUDOMONAS AERUGINOSA FROM WATER SYSTEMS: A REVIEW

2019 ◽  
Vol 8 (5) ◽  
Author(s):  
Kabirdas B. Ghorpade ◽  
Milind Suryawanshi ◽  
Sharda M. Shinde
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Natural Waters ◽  
Water System ◽  
Opportunistic Pathogen ◽  
Water Systems ◽  
Free Living ◽  
Gram Negative ◽  
Physical Conditions ◽  
Wide Range ◽  
Living Bacteria

Pseudomonads free-living bacteria that live primarily in soil, seawater, and fresh water. They also colonize plants and animals. Pseudomonads can grow in distilled water also. Pseudomonas spp., ubiquitous Gram negative bacilli, are found in natural waters such as lakes and rivers. On account of their tolerance to a wide variety of physical conditions and minimal nutrition requirements, Pseudomonas also can colonize biofilms in manmade systems such as drinking water. Pseudomonas aeruginosa is a major human opportunistic pathogen species of this group, which can cause a wide range of infections. In this review we have discussed effect of Bacteria on human health and the methods to control the Pseudomonas aeruginosa in water system. Keywords: Pseudomonas aeruginosa, Bacteriophages, water decontamination, Copper-silver ionization, Ozone, Pathogens.

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