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Molecular Dynamics Study of Helicobacter pylori Urease.

ABSTRACT: Helicobacter pylori have been implicated in an array of gastrointestinal disorders including, but not limited to, gastric and duodenal ulcers and adenocarcinoma. This bacterium utilizes an enzyme, urease, to produce copious amounts of ammonia through urea hydrolysis in order to survive the harsh acidic conditions of the stomach. Molecular dynamics (MD) studies on the H. pylori urease enzyme have been employed in order to study structural features of this enzyme that may shed light on the hydrolysis mechanism. A total of 400 ns of MD simulation time were collected and analyzed in this study. A wide-open flap state previously observed in MD simulations on Klebsiella aerogenes [Roberts et al. J. Am. Chem. Soc.2012, 134, 9934] urease has been identified in the H. pylori enzyme that has yet to be experimentally observed. Critical distances between residues on the flap, contact points in the closed state, and the separation between the active site Ni(2+) ions and the critical histidine ?322 residue were used to characterize flap motion. An additional flap in the active site was elaborated upon that we postulate may serve as an exit conduit for hydrolysis products. Finally we discuss the internal hollow cavity and present analysis of the distribution of sodium ions over the course of the simulation.

SUBMITTER: Minkara MS

PROVIDER: S-EPMC4020587 | biostudies-literature | 2014 May

REPOSITORIES: biostudies-literature

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Molecular Dynamics Study of Helicobacter pylori Urease.

Minkara Mona S MS Ucisik Melek N MN Weaver Michael N MN Merz Kenneth M KM

Journal of chemical theory and computation 20140325 5

Helicobacter pylori have been implicated in an array of gastrointestinal disorders including, but not limited to, gastric and duodenal ulcers and adenocarcinoma. This bacterium utilizes an enzyme, urease, to produce copious amounts of ammonia through urea hydrolysis in order to survive the harsh acidic conditions of the stomach. Molecular dynamics (MD) studies on the H. pylori urease enzyme have been employed in order to study structural features of this enzyme that may shed light ...[more]

PMID: 24839409

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Project description:The well-studied catalytic role of urease, the Ni-dependent conversion of urea into carbon dioxide and ammonia, has been shown to protect Helicobacter pylori against the low pH environment of the stomach lumen. We hypothesized that the abundantly expressed urease protein can play another noncatalytic role in combating oxidative stress via Met residue-mediated quenching of harmful oxidants. Three catalytically inactive urease mutant strains were constructed by single substitutions of Ni binding residues. The mutant versions synthesize normal levels of urease, and the altered versions retained all methionine residues. The three site-directed urease mutants were able to better withstand a hypochlorous acid (HOCl) challenge than a ?ureAB deletion strain. The capacity of purified urease to protect whole cells via oxidant quenching was assessed by adding urease enzyme to nongrowing HOCl-exposed cells. No wild-type cells were recovered with oxidant alone, whereas urease addition significantly aided viability. These results suggest that urease can protect H. pylori against oxidative damage and that the protective ability is distinct from the well-characterized catalytic role. To determine the capability of methionine sulfoxide reductase (Msr) to reduce oxidized Met residues in urease, purified H. pylori urease was exposed to HOCl and a previously described Msr peptide repair mixture was added. Of the 25 methionine residues in urease, 11 were subject to both oxidation and to Msr-mediated repair, as identified by mass spectrometry (MS) analysis; therefore, the oxidant-quenchable Met pool comprising urease can be recycled by the Msr repair system. Noncatalytic urease appears to play an important role in oxidant protection.IMPORTANCE Chronic Helicobacter pylori infection can lead to gastric ulcers and gastric cancers. The enzyme urease contributes to the survival of the bacterium in the harsh environment of the stomach by increasing the local pH. In addition to combating acid, H. pylori must survive host-produced reactive oxygen species to persist in the gastric mucosa. We describe a cyclic amino acid-based antioxidant role of urease, whereby oxidized methionine residues can be recycled by methionine sulfoxide reductase to again quench oxidants. This work expands our understanding of the role of an already acknowledged pathogen virulence factor and specifically expands our knowledge of H. pylori survival mechanisms.

Project description:BackgroundUrease are responsible for several pathogenic states in human as well as in animals and its inhibition is utmost urgent. Clinically used drugs are associated with many side effects; recently several researches have shown that flavonoids have good urease inhibition properties. Morin, a natural flavonoid has been investigated for urease inhibition studies which includes designing of library of morin analogues and their in-silico evaluation with the help of Schrodinger's maestro package of molecular docking software against crystallographic complex of plant enzyme Jack bean urease (PDB ID: 3LA4) followed by synthesis and in vitro evaluation.ResultsBest thirteen derivatives of morin were selected on the basis of their interaction energy and dock score for synthesis and further investigated for in-vitro antioxidant, urease inhibitory and Anti-H. Pylori activity. In-vitro results revealed that a large number of synthesized compounds were found to possess excellent antioxidant and urease Inhibition properties.ConclusionsAmong the synthesized compounds, N-(2-chlorophenyl)-N-((4E)-2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxy-4H-chromen-4-ylidene)thiourea (M2b) and N-(4-bromophenyl)-N-((4E)-2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxy-4H-chromen-4-ylidene)thiourea (M2i) were found to be most potent urease inhibitor and antioxidant with IC50 value 10.74 ± 0.018, 11.12 ± 0.033 and 7.37 ± 0.024, 7.73 ± 0.015and 7.795 ± 0.003 µM. Derivative M2i exhibited good anti-H. pylori activity having MIC = 500 μg/ml and zone of inhibition 15.00 ± 0.00 mm as compared to standard AHA having MIC = 1000 μg/ml and zone of inhibition 9.00 ± 0.50 mm determined against H. Pylori bacterium (ATCC 43504, DSM 4867) by well diffusion technique. Furthermore, molecular docking study explained the binding pattern of synthesized ligand within active cavity of jack bean protein and drug similarity was explained by ADME studies by quikprop module of molecular docking software.

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Molecular Dynamics Study of Helicobacter pylori Urease.

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Molecular Dynamics Study of <i>Helicobacter pylori</i> Urease.

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