scholarly journals Silver Binding to Bacterial Glutaredoxins Observed by NMR

Biophysica ◽  
2021 ◽  
Vol 1 (4) ◽  
pp. 359-376
Author(s):  
Stephanie M. Bilinovich ◽  
Daniel L. Morris ◽  
Jeremy W. Prokop ◽  
Joel A. Caporoso ◽  
Alexandra Taraboletti ◽  
...  
Keyword(s):  
Active Site ◽  
Metal Binding ◽  
Brucella Melitensis ◽  
Size Exclusion ◽  
Oxygen Species ◽  
Metal Binding Site ◽  
Iron Sulfur Cluster ◽  
Iron Sulfur ◽  
Protein Thiols ◽  
Exclusion Chromatography

Glutaredoxins (GRXs) are a class of enzymes used in the reduction of protein thiols and the removal of reactive oxygen species. The CPYC active site of GRX is a plausible metal binding site, but was previously theorized not to bind metals due to its cis-proline configuration. We have shown that not only do several transition metals bind to the CPYC active site of the Brucella melitensis GRX but also report a model of a dimeric GRX in the presence of silver. This metal complex has also been characterized using enzymology, mass spectrometry, size exclusion chromatography, and molecular modeling. Metalation of GRX unwinds the end of the helix displaying the CPYC active site to accommodate dimerization in a way that is similar to iron sulfur cluster binding in related homologs and may imply that metal binding is a more common occurrence in this class of oxidoreductases than previously appreciated.

scholarly journals Characterization of a monoclonal antibody directed against the biologically active site of human interleukin 1.

1986 ◽  
Vol 163 (2) ◽  
pp. 463-468 ◽  
Author(s):  
A Köck ◽  
M Danner ◽  
B M Stadler ◽  
T A Luger
Keyword(s):  
Monoclonal Antibody ◽  
Active Site ◽  
Biological Effects ◽  
Interleukin 1 ◽  
Biologically Active ◽  
Size Exclusion ◽  
Fibroblast Proliferation ◽  
Initial Activity ◽  
Exclusion Chromatography

Human IL-1 was successfully used to produce an anti-IL-1 mAb. Anti-IL-1 (IgG2a) blocked IL-1-mediated thymocyte and fibroblast proliferation, but did not interfere with the biological effects of other lymphokines, such as IL-2 or IL-3. The antibody immunoprecipitated biosynthetically radiolabeled 33, 17, and 4 kD IL-1. An immunoadsorbent column yielded 20% of initial activity, and upon HPLC size-exclusion chromatography, affinity-purified IL-1 had a molecular mass of approximately 4 kD. These results provide first evidence of a monoclonal anti-IL-1 that reacts with different species of IL-1 and apparently binds to an epitope close to the active site of IL-1. Thus, anti-IL-1 IgG may be very helpful for further investigations of the molecular as well as biological characteristics of IL-1 and related mediators.

scholarly journals Functional Comparison of the Two Bacillus anthracis Glutamate Racemases

2007 ◽  
Vol 189 (14) ◽  
pp. 5265-5275 ◽  
Author(s):  
Dylan Dodd ◽  
Joseph G. Reese ◽  
Craig R. Louer ◽  
Jimmy D. Ballard ◽  
M. Ashley Spies ◽  
...  
Keyword(s):  
Bacillus Anthracis ◽  
Active Site ◽  
Genomic Sequence ◽  
Ph Dependence ◽  
Size Exclusion ◽  
Kinetic Properties ◽  
Active Site Residues ◽  
Glutamate Racemase ◽  
Genes Encoding ◽  
Exclusion Chromatography

ABSTRACT Glutamate racemase activity in Bacillus anthracis is of significant interest with respect to chemotherapeutic drug design, because l-glutamate stereoisomerization to d-glutamate is predicted to be closely associated with peptidoglycan and capsule biosynthesis, which are important for growth and virulence, respectively. In contrast to most bacteria, which harbor a single glutamate racemase gene, the genomic sequence of B. anthracis predicts two genes encoding glutamate racemases, racE1 and racE2. To evaluate whether racE1 and racE2 encode functional glutamate racemases, we cloned and expressed racE1 and racE2 in Escherichia coli. Size exclusion chromatography of the two purified recombinant proteins suggested differences in their quaternary structures, as RacE1 eluted primarily as a monomer, while RacE2 demonstrated characteristics of a higher-order species. Analysis of purified recombinant RacE1 and RacE2 revealed that the two proteins catalyze the reversible stereoisomerization of l-glutamate and d-glutamate with similar, but not identical, steady-state kinetic properties. Analysis of the pH dependence of l-glutamate stereoisomerization suggested that RacE1 and RacE2 both possess two titratable active site residues important for catalysis. Moreover, directed mutagenesis of predicted active site residues resulted in complete attenuation of the enzymatic activities of both RacE1 and RacE2. Homology modeling of RacE1 and RacE2 revealed potential differences within the active site pocket that might affect the design of inhibitory pharmacophores. These results suggest that racE1 and racE2 encode functional glutamate racemases with similar, but not identical, active site features.

Mössbauer Studies of the Iron−Sulfur Cluster-Free Hydrogenase:  The Electronic State of the Mononuclear Fe Active Site

2005 ◽  
Vol 127 (29) ◽  
pp. 10430-10435 ◽  
Author(s):  
Seigo Shima ◽  
Erica J. Lyon ◽  
Rudolf K. Thauer ◽  
Bernd Mienert ◽  
Eckhard Bill
Keyword(s):  
Electronic State ◽  
Active Site ◽  
Iron Sulfur Cluster ◽  
Sulfur Cluster ◽  
Mössbauer Studies ◽  
Iron Sulfur

scholarly journals A sensitive core region in the structure of glutathione S-transferases

2003 ◽  
Vol 373 (3) ◽  
pp. 759-765 ◽  
Author(s):  
Jantana WONGSANTICHON ◽  
Thasaneeya HARNNOI ◽  
Albert J. KETTERMAN
Keyword(s):  
Active Site ◽  
Site Directed Mutagenesis ◽  
Size Exclusion ◽  
Single Amino Acid ◽  
Variant Form ◽  
Active Site Residues ◽  
Glutathione S Transferase ◽  
Anopheles Dirus ◽  
Single Amino Acid Change ◽  
Exclusion Chromatography

A variant form of an Anopheles dirus glutathione S-transferase (GST), designated AdGSTD4-4, possesses a single amino acid change of leucine to arginine (Leu-103-Arg). Although residue 103 is outside of the active site, it has major effects on enzymic properties. To investigate these structural effects, site-directed mutagenesis was used to generate mutants by changing the non-polar leucine to alanine, glutamate, isoleucine, methionine, asparagine, or tyrosine. All of the recombinant GSTs showed approximately the same expression level at 25° C. Several of the mutants lacked glutathione (GSH)-binding affinity but were purified by S-hexyl-GSH-based affinity chromatography. However the protein yields (70-fold lower), as well as the GST activity (100-fold lower), of Leu-103-Tyr and Leu-103-Arg purifications were surprisingly low and precluded the performance of kinetic experiments. Size-exclusion chromatography showed that both GSTs Leu-103-Tyr and Leu-103-Arg formed dimers. Using 1-chloro-2,4-dinitrobenzene (CDNB) and GSH substrates to determine kinetic constants it was demonstrated that the other Leu-103 mutants possessed a greater Km towards GSH and a differing Km towards CDNB. The Vmax ranged from 44.7 to 87.0 μmol/min per mg (wild-type, 44.7 μmol/min per mg). Substrate-specificity studies showed different selectivity properties for each mutant. The structural residue Leu-103 affects the active site through H-bond and van-der-Waal contacts with six active-site residues in the GSH binding site. Changes in this interior core residue appear to disrupt internal packing, which affects active-site residues as well as residues at the subunit–subunit interface. Finally, the data suggest that Leu-103 is noteworthy as a sensitive residue in the GST structure that modulates enzyme activity as well as stability.

Impact of the Iron–Sulfur Cluster Proximal to the Active Site on the Catalytic Function of an O2-Tolerant NAD+-Reducing [NiFe]-Hydrogenase

Biochemistry ◽  
2015 ◽  
Vol 54 (2) ◽  
pp. 389-403 ◽  
Author(s):  
Katja Karstens ◽  
Stefan Wahlefeld ◽  
Marius Horch ◽  
Miriam Grunzel ◽  
Lars Lauterbach ◽  
...  
Keyword(s):  
Active Site ◽  
Iron Sulfur Cluster ◽  
Sulfur Cluster ◽  
Catalytic Function ◽  
Iron Sulfur

The importance of iron in the biosynthesis and assembly of [NiFe]-hydrogenases

2014 ◽  
Vol 5 (1) ◽  
pp. 55-70 ◽  
Author(s):  
Constanze Pinske ◽  
R. Gary Sawers
Keyword(s):  
Active Site ◽  
Large Subunit ◽  
Small Subunit ◽  
Transport Systems ◽  
Bacterial Cells ◽  
Carbamoyl Phosphate ◽  
Iron Sulfur Cluster ◽  
Iron Sulfur ◽  
Redox Active ◽  
Cofactor Biosynthesis

Abstract[NiFe]-hydrogenases (Hyd) are redox-active metalloenzymes that catalyze the reversible oxidation of molecular hydrogen to protons and electrons. These enzymes are frequently heterodimeric and have a unique bimetallic active site in their catalytic large subunit and possess a complement of iron sulfur (Fe-S) clusters for electron transfer in the small subunit. Depending on environmental and metabolic requirements, the Fe-S cluster relay shows considerable variation among the Hyd, even employing high potential [4Fe-3S] clusters for improved oxygen tolerance. The general iron sulfur cluster (Isc) machinery is required for small subunit maturation, possibly providing standard [4Fe-4S], which are then modified as required in situ. The [NiFe] cofactor in the active site also has an iron ion to which one CO and two CN- diatomic ligands are attached. Specific accessory proteins synthesize these ligands and insert the cofactor into the apo-hydrogenase large subunit. Carbamoyl phosphate is the precursor of the CN- ligands, and recent experimental evidence suggests that endogenously generated CO2 might be one precursor of CO. Recent advances also indicate how the machineries responsible for cofactor generation obtain iron. Several transport systems for iron into bacterial cells exist; however, in Escherichia coli, it is mainly the ferrous iron transporter Feo and the ferric-citrate siderphore system Fec that are involved in delivering the metal for Hyd biosynthesis. Genetic analyses have provided evidence for the existence of key checkpoints during cofactor biosynthesis and enzyme assembly that ensure correct spatiotemporal maturation of these modular oxidoreductases.

Solution NMR Structure of the Iron–Sulfur Cluster Assembly Protein U (IscU) with Zinc Bound at the Active Site

2004 ◽  
Vol 344 (2) ◽  
pp. 567-583 ◽  
Author(s):  
Theresa A. Ramelot ◽  
John R. Cort ◽  
Sharon Goldsmith-Fischman ◽  
Gregory J. Kornhaber ◽  
Rong Xiao ◽  
...  
Keyword(s):  
Active Site ◽  
Nmr Structure ◽  
Solution Nmr ◽  
Cluster Assembly ◽  
Iron Sulfur Cluster ◽  
Sulfur Cluster ◽  
Iron Sulfur

scholarly journals Theoretical Study on Redox Potential Control of Iron-Sulfur Cluster by Hydrogen Bonds: A Possibility of Redox Potential Programming

Molecules ◽  
2021 ◽  
Vol 26 (20) ◽  
pp. 6129
Author(s):  
Iori Era ◽  
Yasutaka Kitagawa ◽  
Natsumi Yasuda ◽  
Taigo Kamimura ◽  
Naoka Amamizu ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Redox Potential ◽  
Active Site ◽  
Density Functional ◽  
Redox Potentials ◽  
Iron Sulfur Cluster ◽  
Potential Control ◽  
Iron Sulfur ◽  
And Shifts ◽  
Reduced State

The effect of hydrogen bonds around the active site of Anabaena [2Fe-2S] ferredoxin (Fd) on a vertical ionization potential of the reduced state (IP(red)) is examined based on the density functional theory (DFT) calculations. The results indicate that a single hydrogen bond increases the relative stability of the reduced state, and shifts IP(red) to a reductive side by 0.31–0.33 eV, regardless of the attached sulfur atoms. In addition, the IP(red) value can be changed by the number of hydrogen bonds around the active site. The results also suggest that the redox potential of [2Fe-2S] Fd is controlled by the number of hydrogen bonds because IP(red) is considered to be a major factor in the redox potential. Furthermore, there is a possibility that the redox potentials of artificial iron-sulfur clusters can be finely controlled by the number of the hydrogen bonds attached to the sulfur atoms of the cluster.

scholarly journals Redox response of iron-sulfur glutaredoxin GRXS17 activates its holdase activity to protect plants from heat stress

2020 ◽  
Author(s):  
Laura Martins ◽  
Johannes Knuesting ◽  
Laetitia Bariat ◽  
Avilien Dard ◽  
Sven A. Freibert ◽  
...  
Keyword(s):  
Heat Stress ◽  
Active Site ◽  
Disulfide Bonds ◽  
Dependent Manner ◽  
Plant Tolerance ◽  
Iron Sulfur Cluster ◽  
Subsequent Formation ◽  
Iron Sulfur ◽  
Root Meristematic Cells ◽  
Living Organisms

ABSTRACTLiving organisms use a large panel of mechanisms to protect themselves from environmental stress. Particularly, heat stress induces misfolding and aggregation of proteins which are guarded by chaperone systems. Here, we examine the function the glutaredoxin GRXS17, a member of thiol reductases families in the model plant Arabidopsis thaliana. GRXS17 is a nucleocytosolic monothiol glutaredoxin consisting of an N-terminal thioredoxin (TRX)-domain and three CGFS-active site motif-containing GRX-domains that coordinate three iron-sulfur (Fe-S) clusters in a glutathione (GSH)-dependent manner. As a Fe-S cluster-charged holoenzyme, GRXS17 is likely involved in the maturation of cytosolic and nuclear Fe-S proteins. In addition to its role in cluster biogenesis, we showed that GRXS17 presents both foldase and redox-dependent holdase activities. Oxidative stress in combination with heat stress induces loss of its Fe-S clusters followed by subsequent formation of disulfide bonds between conserved active site cysteines in the corresponding TRX domains. This oxidation leads to a shift of GRXS17 to a high-MW complex and thus, activates its holdase activity. Moreover, we demonstrate that GRXS17 is specifically involved in plant tolerance to moderate high temperature and protects root meristematic cells from heat-induced cell death. Finally, we showed that upon heat stress, GRXS17 changes its client proteins, possibly to protect them from heat injuries. Therefore, we propose that the iron-sulfur cluster enzyme glutaredoxin GRXS17 is an essential guard to protect proteins against moderate heat stress, likely through a redox-dependent chaperone activity. All in all, we reveal the mechanism of an Fe-S cluster-dependent activity shift, turning the holoenzyme GRXS17 into a holdase that prevents damage caused by heat stress.

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