scholarly journals Functional design of bacterial superoxide:quinone oxidoreductase

2021 ◽  
Author(s):  
Christoph von Ballmoos ◽  
Abbas Abou-Hamdan ◽  
Roman Mahler ◽  
Philipp Grossenbacher ◽  
Olivier Biner ◽  
...  
Keyword(s):  
Defense Mechanisms ◽  
Forward Direction ◽  
Superoxide Reductase ◽  
Diffusion Limit ◽  
Cellular Functions ◽  
Midpoint Potential ◽  
E Coli ◽  
Cellular Defense ◽  
Cytochrome B561 ◽  
Hydroxyl Anion

The superoxide anion - molecular oxygen reduced by a single electron - is produced in large amounts by enzymatic and adventitious reactions and can perform a range of cellular functions, including bacterial warfare and iron uptake, signalling and host immune response in eukaryotes. However, it also serves as precursor for more deleterious species such as the hydroxyl anion or peroxynitrite and therefore, cellular defense mechanisms for superoxide neutralization have evolved. In addition to the soluble proteins superoxide dismutase and superoxide reductase, recently the membrane embedded diheme cytochrome b561 (CybB) from E. coli has been proposed to act as a superoxide:quinone oxidoreductase. Here, we confirm superoxide and cellular ubiquinones or menaquinones as natural substrates and show that quinone binding to the enzyme accelerates the reaction with superoxide. The reactivity of the substrates is in accordance with the here determined midpoint potential of the two b hemes (+48 and -23 mV / NHE). Our data suggest that the enzyme can work near the diffusion limit in the forward direction and can also catalyse the reverse reaction efficiently under physiological conditions. The data is discussed in context of described cytochrome b561 proteins and potential physiological roles of CybB.

scholarly journals In Vitro Reconstitution of an NADPH-Dependent Superoxide Reduction Pathway from Pyrococcus furiosus

2005 ◽  
Vol 71 (3) ◽  
pp. 1522-1530 ◽  
Author(s):  
Amy M. Grunden ◽  
Francis E. Jenney ◽  
Kesen Ma ◽  
Mikyoung Ji ◽  
Michael V. Weinberg ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Pyrococcus Furiosus ◽  
Expression System ◽  
Anaerobic Bacteria ◽  
Flavin Mononucleotide ◽  
Superoxide Reductase ◽  
Recombinant Enzymes ◽  
Significant Similarity ◽  
Midpoint Potential

ABSTRACT A scheme for the detoxification of superoxide in Pyrococcus furiosus has been previously proposed in which superoxide reductase (SOR) reduces (rather than dismutates) superoxide to hydrogen peroxide by using electrons from reduced rubredoxin (Rd). Rd is reduced with electrons from NAD(P)H by the enzyme NAD(P)H:rubredoxin oxidoreductase (NROR). The goal of the present work was to reconstitute this pathway in vitro using recombinant enzymes. While recombinant forms of SOR and Rd are available, the gene encoding P. furiosus NROR (PF1197) was found to be exceedingly toxic to Escherichia coli, and an active recombinant form (rNROR) was obtained via a fusion protein expression system, which produced an inactive form of NROR until cleavage. This allowed the complete pathway from NAD(P)H to the reduction of SOR via NROR and Rd to be reconstituted in vitro using recombinant proteins. rNROR is a 39.9-kDa protein whose sequence contains both flavin adenine dinucleotide (FAD)- and NAD(P)H-binding motifs, and it shares significant similarity with known and putative Rd-dependent oxidoreductases from several anaerobic bacteria, both mesophilic and hyperthermophilic. FAD was shown to be essential for activity in reconstitution assays and could not be replaced by flavin mononucleotide (FMN). The bound FAD has a midpoint potential of −173 mV at 23°C (−193 mV at 80°C). Like native NROR, the recombinant enzyme catalyzed the NADPH-dependent reduction of rubredoxin both at high (80°C) and low (23°C) temperatures, consistent with its proposed role in the superoxide reduction pathway. This is the first demonstration of in vitro superoxide reduction to hydrogen peroxide using NAD(P)H as the electron donor in an SOR-mediated pathway.

DIAGNOSTIC LUNG PUNCTURE IN THE PNEUMONIAS OF INFANTS AND CHILDREN

PEDIATRICS ◽  
1969 ◽  
Vol 44 (4) ◽  
pp. 486-492
Author(s):  
Jerome O. Klein
Keyword(s):  
Defense Mechanisms ◽  
Underlying Disease ◽  
Etiologic Agent ◽  
Upper Respiratory Tract ◽  
E Coli ◽  
Pure Cultures ◽  
Lung Puncture ◽  
Lower Respiratory Disease ◽  
And Staphylococcus Aureus ◽  
Etiologic Diagnosis

Lung punctures were performed on 32 occasions in 28 infants with pneumonia to assist in specific bacteriologic diagnosis. The aspirates yielded pure cultures of Diplococcus pneumoniae and Staphylococcus aureus each in four patients and E. coli in two patients. The procedure is performed as for a thoracentesis and requires no special instruments. Three children had pneumothoraces and one had a small hemoptysis following the procedure, but only one child exhibited even minimal respiratory distress as a result of the tap. The literature on lung aspirates was reviewed with respect to the value and potential liability of the procedure. At present, diagnostic lung punctures should be considered in three groups of children with lower respiratory disease: (1) the critically ill child in whom a specific etiologic diagnosis is of major importance to guide antimicrobial therapy, (2) the child who has deteriorated while on therapy and in whom an etiologic agent is not available from the usual upper respiratory tract cultures, and (3) the child with pneumonia complicated by underlying disease or drugs limiting normal host defense mechanisms. In these three instances, the advantages of a specific etiologic diagnosis outweighs the small risk from the lung puncture.

The role of corneal crystallins in the cellular defense mechanisms against oxidative stress

2008 ◽  
Vol 19 (2) ◽  
pp. 100-112 ◽  
Author(s):  
Natalie Lassen ◽  
William J. Black ◽  
Tia Estey ◽  
Vasilis Vasiliou
Keyword(s):  
Oxidative Stress ◽  
Defense Mechanisms ◽  
Cellular Defense

scholarly journals Comparative characterisation of Plasmodium falciparum Hsp70-1 relative to E. coli DnaK reveals functional specificity of the parasite chaperone

2020 ◽  
Author(s):  
Charity Mekgwa Lebepe ◽  
Pearl Rutendo Matambanadzo ◽  
Xolani Henry Makhoba ◽  
Ikechukwu Achilonu ◽  
Tawanda Zininga ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Molecular Chaperone ◽  
Chimeric Protein ◽  
Cellular Functions ◽  
E Coli ◽  
Adenosylmethionine Decarboxylase ◽  
Comparative Structure ◽  
Functional Features ◽  
Self Association

ABSTRACTHsp70 is one of the most prominent molecular chaperones. Although Hsp70s from various organisms are generally conserved, they exhibit specialised cellular functions. It remains to be fully understood how these highly conserved molecules exhibit specialised functional features. Plasmodium falciparum Hsp70-1 (PfHsp70-1) is a cytosol localised molecular chaperone that is implicated in the cyto-protection and pathogenicity of the malaria parasite. In the current study, we investigated the comparative structure-function features of PfHsp70-1 relative to its homologue, E. coli Hsp70 (DnaK) and a chimeric protein, KPf, that was constituted by the ATPase domain of DnaK and the substrate binding domain (SBD) of PfHsp70-1. Recombinant forms of all the three Hsp70s exhibited similar secondary and tertiary structural fold. We further established that compared to DnaK, both KPf and PfHsp70-1 were more stable to heat stress and exhibited higher basal ATPase activity. A recombinant P. falciparum Hsp40 (PfHsp40) stimulated the ATPase activities of all the three Hsp70s. In addition, both PfHsp70-1 and KPf exhibited preference for asparagine rich peptides as opposed to DnaK. Furthermore, all the three proteins exhibited self-association capabilities in vitro. Recombinant P. falciparum adenosylmethionine decarboxylase (PfAdoMetDC) co-expressed in E. coli with either KPf or PfHsp70-1 was produced as a fully folded product. On the other hand, co-expression of PfAdoMetDC with heterologous DnaK in E. coli did not promote folding of the former. These findings demonstrated that the SBD of PfHsp70-1 regulates several functional features of the protein and that this molecular chaperone is tailored to facilitate folding of plasmodial proteins.

scholarly journals Oxidative damage and cellular defense mechanisms in sea urchin models of aging

2013 ◽  
Vol 63 ◽  
pp. 254-263 ◽  
Author(s):  
Colin Du ◽  
Arielle Anderson ◽  
Mae Lortie ◽  
Rachel Parsons ◽  
Andrea Bodnar
Keyword(s):  
Oxidative Damage ◽  
Sea Urchin ◽  
Defense Mechanisms ◽  
Cellular Defense

scholarly journals Cooperative Immune Suppression by Escherichia coli and Shigella Effector Proteins

2018 ◽  
Vol 86 (4) ◽  
Author(s):  
Maarten F. de Jong ◽  
Neal M. Alto
Keyword(s):  
Escherichia Coli ◽  
Defense Mechanisms ◽  
Immune Defense ◽  
Effector Proteins ◽  
Innate Immune ◽  
Host Cells ◽  
Secretion Systems ◽  
Content Type ◽  
E Coli ◽  
Type Iii Secretion Systems

ABSTRACT The enteric attaching and effacing (A/E) pathogens enterohemorrhagic Escherichia coli (EHEC) and enteropathogenic E. coli (EPEC) and the invasive pathogens enteroinvasive E. coli (EIEC) and Shigella encode type III secretion systems (T3SS) used to inject effector proteins into human host cells during infection. Among these are a group of effectors required for NF-κB-mediated host immune evasion. Recent studies have identified several effector proteins from A/E pathogens and EIEC/ Shigella that are involved in suppression of NF-κB and have uncovered their cellular and molecular functions. A novel mechanism among these effectors from both groups of pathogens is to coordinate effector function during infection. This cooperativity among effector proteins explains how bacterial pathogens are able to effectively suppress innate immune defense mechanisms in response to diverse classes of immune receptor signaling complexes (RSCs) stimulated during infection.

#10: Fever and neutropenia. 10 years surveillance in a pediatric Mexican hospital

2021 ◽  
Vol 10 (Supplement_1) ◽  
pp. S15-S15
Author(s):  
E Sánchez-Medina ◽  
A Reyes-Hernández ◽  
A Severiano-Tellez
Keyword(s):  
Septic Shock ◽  
Defense Mechanisms ◽  
Antibiotic Use ◽  
Infectious Complications ◽  
E Coli ◽  
Pediatric Cancer Patients ◽  
Leukemia Treatment ◽  
Criteria For Diagnosis ◽  
Healthcare Associated ◽  
Epidemiologic Characteristics

Abstract Background Fever and neutropenia, is a very common complication of chemotherapy in the treatment of cancer. It could happen in 10–50% of patients with solid tumors and more than 80% of patients with blood cancer. During leukemia treatment is very important first defense mechanisms integrity, such as skin, mucous membranes, Tlaxcala Children’s Hospital is a pediatric general hospital, located in the center of Mexico and is where the pediatric cancer patients are treated, with almost 30 new cases by year, treatment with chemotherapy and as an adverse event fever and neutropenia, which increases morbidity and mortality Methods We conducted an observational, descriptive, and analytic study aiming to identify fever and neutropenic events in ALL patients, their epidemiologic characteristics, antibiotic use, isolation and antibiogram, and outcome. Results We reviewed 124 files from ALL patients between 2007–2017, we found 204 cases, 70 (33.8%) at induction, 18.6% consolidation, reinduction 17.6%, maintenance 14.2%. Out of 204 cases, we documented 177 with fever and neutropenia, 15 events of septic shock and 12 with fever and neutropenia with an identifiable source; the first-line antibiotic for fever and neutropenia was ceftazidime/amikacin, and for septic shock cefepime with an aminoglycoside, we found 3.39%, 20%, and 0% deaths from each group. Patients with fever and neutropenia with or without identifiable source had a length-stay average of 9.8 days compared with 30 days in patients with septic shock, CRP average was 12.47 mg/dL in the patients who survived and 8.23 mg/dL in those who did not. We found a very low positivity in cultures, and in most cases, those cultures did not meet criteria for diagnosis, the most common bacteria identified were E. coli, P. aeruginosa. Conclusions This is the first approach to get a better knowledge about infectious complications in patients with ALL, these findings could lead to identifying opportunities to improve diagnosis and treatment which lead to reducing cost, morbidity, healthcare-associated infections.

scholarly journals MazG, a Nucleoside Triphosphate Pyrophosphohydrolase, Interacts with Era, an Essential GTPase in Escherichia coli

2002 ◽  
Vol 184 (19) ◽  
pp. 5323-5329 ◽  
Author(s):  
Junjie Zhang ◽  
Masayori Inouye
Keyword(s):  
Escherichia Coli ◽  
Direct Interaction ◽  
Kanamycin Resistance ◽  
Nucleoside Triphosphate ◽  
Cellular Functions ◽  
Genomic Libraries ◽  
E Coli ◽  
Yeast Two Hybrid System ◽  
Nucleoside Triphosphate Pyrophosphohydrolase

ABSTRACT Era is an essential GTPase in Escherichia coli, and Era has been implicated in a number of cellular functions. Homologues of Era have been identified in various bacteria and some eukaryotes. Using the era gene as bait in the yeast two-hybrid system to screen E. coli genomic libraries, we discovered that Era interacts with MazG, a protein of unknown function which is highly conserved among bacteria. The direct interaction between Era and MazG was also confirmed in vitro, being stronger in the presence of GDP than in the presence of GTPγS. MazG was characterized as a nucleoside triphosphate pyrophosphohydrolase which can hydrolyze all eight of the canonical ribo- and deoxynucleoside triphosphates to their respective monophosphates and PPi, with a preference for deoxynucleotides. A mazG deletion strain of E. coli was constructed by replacing the mazG gene with a kanamycin resistance gene. Unlike mutT, a gene for another conserved nucleotide triphosphate pyrophosphohydrolase that functions as a mutator gene, the mazG deletion did not result in a mutator phenotype in E. coli.

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