scholarly journals The organomercurial lyase Merb possesses unique metal-binding properties

2014 ◽  
Vol 70 (a1) ◽  
pp. C1680-C1680
Author(s):  
Haytham Wahba ◽  
Ahmed Mansour ◽  
Julien Vanasse ◽  
Laurent Cappadocia ◽  
Jurgen Sygusch ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Metal Binding ◽  
Catalytic Triad ◽  
Bacterial Strains ◽  
Paramagnetic Resonance ◽  
Mer Operon ◽  
X Ray ◽  
E Coli ◽  
X Ray Crystallography ◽  
Organomercurial Lyase

Select bacterial strains survive in mercury-contaminated environments due to acquisition of a transferable genetic element known as the mer operon. The mer operon typically encodes for a series of proteins that includes two enzymes, MerA and MerB. The organomercurial lyase (MerB) cleaves carbon-mercury bonds of organomercurial compounds yielding ionic mercury Hg (II) and a reduced-carbon compound. The Hg (II) ion product remains bounds until it is shuttled directly to the mercuric ion reductase (MerA) to be reduced. Based on NMR spectroscopy and X-ray crystallography studies1, we have determined that Cys96, Asp99 and Cys159 of E. Coli MerB form a catalytic triad required for cleavage of the carbon-Hg bond and binding of the Hg (II) ion product. The three catalytic residues are conserved in 61 of 65 known variants of MerB and the four remaining variants retain both cysteine residues, but contain a serine in place of Asp99. Given its unique activity, we have examined the role of serine as a catalytic residue and the ability of MerB to cleave other organometals such as organotin (known substrates or inhibitors) and organolead compounds. Soaking MerB crystals with either dimethyltindibromide or trimethylleadchloride compound indicates that MerB crystals have the capacity to cleave both carbon-Sn and carbon-Pb bonds, and we have determined crystal structures of a MerB-Sn and a MerB-Pb complex. Furthermore, substitution of Ser for Asp99 (MerB D99S) in E. coli MerB alters the metal-binding specificity, as MerB D99S chelated an unknown metal during its purification. X-ray crystallography, ICP-MS and electron paramagnetic resonance (EPR) studies were performed to identify the unknown metal and the results of these studies will be presented. Given that mercury contaminated sites are often contaminated with other heavy metals, these studies indicate that other heavy metals may have important implications when using MerA and MerB in bioremediation of organomercurial compounds.

scholarly journals Silver Nanoparticles from Oregano Leaves’ Extracts as Antimicrobial Components for Non-Infected Hydrogel Contact Lenses

2021 ◽  
Vol 22 (7) ◽  
pp. 3539
Author(s):  
Anastasia Meretoudi ◽  
Christina N. Banti ◽  
Panagiotis K. Raptis ◽  
Christina Papachristodoulou ◽  
Nikolaos Kourkoumelis ◽  
...  
Keyword(s):  
Silver Nanoparticles ◽  
Contact Lenses ◽  
Attenuated Total Reflection ◽  
Bacterial Strains ◽  
Scanning Calorimetry ◽  
X Ray ◽  
E Coli ◽  
Polymer Hydrogels ◽  
20 Nm ◽  
And Staphylococcus Aureus

The oregano leaves’ extract (ORLE) was used for the formation of silver nanoparticles (AgNPs(ORLE)). ORLE and AgNPs(ORLE) (2 mg/mL) were dispersed in polymer hydrogels to give the pHEMA@ORLE_2 and pHEMA@AgNPs(ORLE)_2 using hydroxyethyl–methacrylate (HEMA). The materials were characterized by X-ray fluorescence (XRF) spectroscopy, X-ray powder diffraction analysis (XRPD), thermogravimetric differential thermal analysis (TG-DTA), derivative thermogravimetry/differential scanning calorimetry (DTG/DSC), ultraviolet (UV-Vis), and attenuated total reflection mode (ATR-FTIR) spectroscopies in solid state and UV–Vis in solution. The crystallite size value, analyzed with XRPD, was determined at 20 nm. The antimicrobial activity of the materials was investigated against Gram-negative bacterial strains Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli). The Gram-positive ones of the genus of Staphylococcus epidermidis (S. epidermidis) and Staphylococcus aureus (S. aureus) are known to be involved in microbial keratitis by the means of inhibitory zone (IZ), minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC). The IZs, which developed upon incubation of P. aeruginosa, E. coli, S. epidermidis, and S. aureus with paper discs soaked in 2 mg/mL of AgNPs(ORLE), were 11.7 ± 0.7, 13.5 ± 1.9, 12.7 ± 1.7, and 14.3 ± 1.7 mm. When the same dose of ORLE was administrated, the IZs were 10.2 ± 0.7, 9.2 ± 0.5, 9.0 ± 0.0, and 9.0 ± 0.0 mm. The percent of bacterial viability when they were incubated over the polymeric hydrogel discs of pHEMA@AgNPs(ORLE)_2 was interestingly low (66.5, 88.3, 77.7, and 59.6%, respectively, against of P. aeruginosa, E. coli, S. epidermidis, and S. aureus) and those of pHEMA@ORLE_2 were 89.3, 88.1, 92.8, and 84.6%, respectively. Consequently, pHEMA@AgNPs(ORLE)_2 could be an efficient candidate toward the development of non-infectious contact lenses.

scholarly journals An Isolable Mononuclear Palladium(I) Amido Complex

2021 ◽  
Author(s):  
jian Liu ◽  
Melissa Bollmeyer ◽  
Yujeong Kim ◽  
Dengmengfei Xiao ◽  
Samantha N. Macmillan ◽  
...  
Keyword(s):  
Theoretical Study ◽  
Bond Cleavage ◽  
Primary Amines ◽  
Dispersion Force ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
X Ray Crystallography ◽  
Pauli Repulsion ◽  
Catalyzed Reactions ◽  
Electron Paramagnetic

Mononuclear Pd(I) species are putative intermediates in Pd-catalyzed reactions, but our knowledge about them is limited due to difficulties in accessing them. Herein, we report the isolation of a Pd(I) amido complex, [(BINAP)Pd(NHArTrip )] (BINAP = 2,2′- bis(diphenylphosphino)-1,1′-binaphthalene, ArTrip = 2,6-bis(2’,4’,6’-triisopropylphenyl)phenyl), from the reaction of (BINAP)PdCl2 with LiNHArTrip. This Pd(I) amido species has been characterized by X-ray crystallography, electron paramagnetic resonance, and multi-edge Pd Xray absorption spectroscopy. Theoretical study revealed that, while the 3-electron-2-center π interaction between Pd and N in the Pd(I) complex imposes severe Pauli repulsion in its Pd–N bond, pronounced attractive inter-ligand dispersion force aids its stabilization. In accord with its electronic features, reactions of homolytic Pd–N bond cleavage and deprotonation of primary amines are observed on the Pd(I) amido complex.

scholarly journals An Efficient Disinfectant, Composite Material {SLS@[Zn3(CitH)2]} as Ingredient for Development of Sterilized and Non Infectious Contact Lens

Antibiotics ◽  
2019 ◽  
Vol 8 (4) ◽  
pp. 213 ◽  
Author(s):  
V.A. Karetsi ◽  
C.N. Banti ◽  
N. Kourkoumelis ◽  
C. Papachristodoulou ◽  
C.D. Stalikas ◽  
...  
Keyword(s):  
Contact Lenses ◽  
Fluorescence Analysis ◽  
Gram Positive ◽  
Gram Negative ◽  
X Ray ◽  
E Coli ◽  
X Ray Crystallography ◽  
Ft Ir ◽  
And Staphylococcus Aureus ◽  
Ft Raman

The [Zn3(CitH)2] (1) (CitH4= citric acid), was dispersed in sodium lauryl sulphate (SLS) to form the micelle of SLS@[Zn3(CitH)2] (2). This material 2 was incorporated in hydrogel made by hydroxyethyl-methacrylate (HEMA), an ingredient of contact lenses, toward the formation of pHEMA@(SLS@[Zn3(CitH)2]) (3). Samples of 1 and 2 were characterized by UV-Vis, 1H-NMR, FT-IR, FT-Raman, single crystal X-ray crystallography, X-ray fluorescence analysis, atomic absorption and TG/DTA/DSC. The antibacterial activity of 1–3 as well as of SLS against Gram-positive (Staphylococcus epidermidis (St. epidermidis) and Staphylococcus aureus (St. aureus)) and Gram-negative (Pseudomonas aeruginosa (PAO1), and Escherichia coli (E. coli)) bacteria was evaluated by the means of minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and inhibitory zone (IZ). 2 showed 10 to 20-fold higher activity than 1 against the bacteria tested. Moreover the 3 decreases the abundance of Gram-positive microbes up to 30% (St. aureus) and up to 20% (PAO1) the Gram-negative ones. The noteworthy antimicrobial activity of the obtained composite 3 suggests an effective antimicrobial additive for infection-free contact lenses.

Elucidating factors important for monovalent cation selectivity in enzymes: E. coli β-galactosidase as a model

2015 ◽  
Vol 17 (16) ◽  
pp. 10899-10909 ◽  
Author(s):  
Robert W. Wheatley ◽  
Douglas H. Juers ◽  
Bogdan B. Lev ◽  
Reuben E. Huber ◽  
Sergei Yu. Noskov
Keyword(s):  
Monovalent Cation ◽  
Computational Simulations ◽  
X Ray ◽  
E Coli ◽  
X Ray Crystallography ◽  
Cation Selectivity

X-ray crystallography and computational simulations reveal novel mechanisms important for Na+/K+selectivity in enzymes.

scholarly journals Probing the active site of the sugar isomerase domain from E. coli arabinose-5-phosphate isomerase via X-ray crystallography

2010 ◽  
Vol 19 (12) ◽  
pp. 2430-2439 ◽  
Author(s):  
Louise J. Gourlay ◽  
Silvia Sommaruga ◽  
Marco Nardini ◽  
Paola Sperandeo ◽  
Gianni Dehò ◽  
...  
Keyword(s):  
Active Site ◽  
X Ray ◽  
E Coli ◽  
X Ray Crystallography

Two new zinc(II) and mercury(II) complexes based on N,N′-(cyclohexane-1,2-diylidene)bis(4-fluorobenzohydrazide): synthesis, crystal structures and antibacterial activities

2020 ◽  
Vol 76 (5) ◽  
pp. 476-482
Author(s):  
Al-Ameen Bariz OmarAli ◽  
Ahmed Jasim M. Al-Karawi ◽  
Adil A. Awad ◽  
Necmi Dege ◽  
Sevgi Kansız ◽  
...  
Keyword(s):  
Organic Ligand ◽  
Antibacterial Activities ◽  
Structural Features ◽  
Bacterial Strains ◽  
Tetrahedral Geometry ◽  
X Ray ◽  
X Ray Crystallography ◽  
Growth Inhibitory ◽  
The Difference

Reaction of N,N′-(cyclohexane-1,2-diylidene)bis(4-fluorobenzohydrazide), C20H18F2N4O2, (LF ), with zinc chloride and mercury(II) chloride produced different types and shapes of neutral coordination complexes, namely, dichlorido[N,N′-(cyclohexane-1,2-diylidene)bis(4-fluorobenzohydrazide)-κ2 N,O]zinc(II), [ZnCl2(C20H18F2N4O2)], (1), and dichlorido[N,N′-(cyclohexane-1,2-diylidene)bis(4-fluorobenzohydrazide)-κ4 O,N,N′,O′]mercury(II), [HgCl2(C20H18F2N4O2)], (2). The organic ligand and its metal complexes are characterized using various techniques: IR, UV–Vis and nuclear magnetic resonance (NMR) spectroscopies, in addition to powder X-ray diffraction (PXRD), single-crystal X-ray crystallography and microelemental analysis. Depending upon the data from these analyses and measurements, a typical tetrahedral geometry was confirmed for zinc complex (1), in which the ZnII atom is located outside the bis(benzhydrazone) core. The HgII atom in (2) is found within the core and has a common octahedral structure. The in vitro antibacterial activities of the prepared compounds were evaluated against two different bacterial strains, i.e. gram positive Bacillus subtilis and gram negative Pseudomonas aeruginosa bacteria. The prepared compounds exhibited differentiated growth-inhibitory activities against these two bacterial strains based on the difference in their lipophilic nature and structural features.

scholarly journals The C-terminal tail of the bacterial translocation ATPase SecA modulates its activity

2018 ◽  
Author(s):  
Mohammed Jamshad ◽  
Timothy J. Knowles ◽  
Scott A. White ◽  
Douglas G. Ward ◽  
Fiyaz Mohammed ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Metal Binding ◽  
Cytoplasmic Membrane ◽  
Protein Recognition ◽  
X Ray ◽  
Ribosome Binding ◽  
X Ray Crystallography ◽  
Substrate Protein ◽  
Metal Binding Domain

AbstractIn bacteria, the translocation of a subset of proteins across the cytoplasmic membrane by the Sec machinery requires SecA. Although SecA can recognise nascent polypeptides, the mechanism of cotranslational substrate protein recognition is not known. Here, we investigated the role of the C-terminal tail (CTT) of SecA, which consists of a flexible linker (FLD) and a small metal-binding domain (MBD), in its interaction with nascent polypeptides. Phylogenetic analysis and ribosome binding experiments indicated that the MBD interacts with 70S ribosomes. Disruption of the entire CTT or the MBD alone had opposing effects on ribosome binding, substrate-protein binding, ATPase activity and in vivo function. Autophotocrosslinking, mass spectrometry, x-ray crystallography and small-angle x-ray scattering experiments provided insight into the CTT-mediated conformational changes in SecA. Finally, photocrosslinking experiments indicated that binding of SecA to substrate protein affected its interaction with the ribosome. Taken together, our results suggest a mechanism for substrate protein recognition.Impact StatementSecA is an evolutionarily conserved ATPase that is required for the translocation of a subset of proteins across the cytoplasmic membrane in bacteria. We investigated how SecA recognises its substrate proteins at the ribosome as they are still being synthesised (i.e. cotranslationally).

Bismuth(III) Thiophosphinates: Understanding How a Small Atomic Change Influences Antibacterial Activity and Mammalian Cell Viability

2020 ◽  
Vol 73 (12) ◽  
pp. 1226
Author(s):  
Dimuthu C. Senevirathna ◽  
Rebekah N. Duffin ◽  
Liam J. Stephens ◽  
Megan E. Herdman ◽  
Melissa V. Werrett ◽  
...  
Keyword(s):  
Antibacterial Activity ◽  
Cell Viability ◽  
Mammalian Cell ◽  
Mammalian Cells ◽  
Bacterial Strains ◽  
X Ray Diffraction ◽  
Gram Negative ◽  
X Ray ◽  
X Ray Crystallography ◽  
Biological Studies

Diphenylphosphinothioic acid (HSP(=O)Ph2) and diphenylphosphinodithioic acid (HSP(=S)Ph2) have been used to synthesise four BiIII complexes: 1 [Bi(SP(=O)Ph2)3], 2 [BiPh(SP(=O)Ph2)2], 3 [BiPh2(SP(=O)Ph2)], and 4 [Bi(SP(=S)Ph2)3], using BiPh3 and [Bi(OtBu)3] as bismuth sources. The complexes have been characterised by NMR spectroscopy, mass spectrometry, infrared spectroscopy, powder X-ray diffraction, and singe crystal X-ray crystallography (2–4). Biological studies indicated that despite complexes 2 and 3 reducing mammalian cell viability, their antibacterial activity provides a good degree of selectivity towards both Gram positive and Gram negative bacterial strains. The minimum inhibitory concentrations for complexes 2 and 3 are in the range of 0.52–5.5µM towards the bacteria tested. Homoleptic complexes 1 and 4 were generally less active towards both bacterial and mammalian cells.

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