Synthesis, Properties, and Electrochemical Proton Reduction of a Homoleptic Tetrathiolato Ni-Site Model of [NiFe]-Hydrogenase.

[NiFe]-hydrogenase enzymes process H at a nonplanar tetracysteinato-Ni site, the sole participator in proton binding/redox chemistry during turnover. With the objective of assessing whether a simple tetrahedral/tetrathiolato-Ni core could promote H evolution reaction (HER), we synthesized (EtN)[Ni(S--CF-Ph)] () employing -trifluoromethylbenzenethiolate (S--CF-Ph) as a Ni-site analog of [NiFe]-hydrogenase. Spectroscopic measurements and X-ray crystallography confirm the distorted tetrahedral geometry of .

Nucleotide- and metalloid-driven conformational changes in the arsenite efflux ATPase ArsA.

Arsenite (As) is toxic to all organisms due to its ability to tightly bind exposed thiols within cells. An important As resistance mechanism in prokaryotes involves proteins encoded by the operon. A central component of the operon in many bacteria is the cytoplasmic ATPase, ArsA, which orchestrates a series of nucleotide-dependent handoffs, starting with the capture of As by the ArsD metallochaperone and culminating in its removal from the cell by the ArsB efflux pump.

The zinc metalloprotein MigC impacts cell wall biogenesis through interactions with an essential Mur ligase in Acinetobacter baumannii.

To colonize and survive in the host, bacterial pathogens like Acinetobacter baumannii must acquire zinc (Zn). To maintain Zn homeostasis, A. baumannii synthesizes proteins of the COG0523 family which are predicted to chaperone Zn to metalloproteins.

Fpa (YlaN) is an iron(II) binding protein that functions to relieve Fur-mediated repression of gene expression in .

Iron (Fe) is a trace nutrient required by nearly all organisms. As a result of the demand for Fe and the toxicity of non-chelated cytosolic ionic Fe, regulatory systems have evolved to tightly balance Fe acquisition and usage while limiting overload. In most bacteria, including the mammalian pathogen , the ferric uptake regulator (Fur) is the primary transcriptional regulator controlling the transcription of genes that code for Fe uptake and utilization proteins.

ATH434, a promising iron-targeting compound for treating iron regulation disorders.

Cytotoxic accumulation of loosely bound mitochondrial Fe2+ is a hallmark of Friedreich's Ataxia (FA), a rare and fatal neuromuscular disorder with limited therapeutic options. There are no clinically approved medications targeting excess Fe2+ associated with FA or the neurological disorders Parkinson's disease and Multiple System Atrophy. Traditional iron-chelating drugs clinically approved for systemic iron overload that target ferritin-stored Fe3+ for urinary excretion demonstrated limited efficacy in FA and exacerbated ataxia.

Coupling of zinc and GTP binding drives G-domain folding in Acinetobacter baumannii ZigA.

COG0523 proteins, also known as nucleotide-dependent metallochaperones, are a poorly understood class of small P-loop G3E GTPases. Multiple family members play critical roles in bacterial pathogen survival during an infection as part of the adaptive response to host-mediated "nutritional immunity." Our understanding of the structure, dynamics, and molecular-level function of COG0523 proteins, apart from the eukaryotic homolog, Zng1, remains in its infancy.

Characterization of the Zinc Uptake Repressor (Zur) from .

Bacterial cells tightly regulate the intracellular concentrations of essential transition metal ions by deploying a panel of metal-regulated transcriptional repressors and activators that bind to operator-promoter regions upstream of regulated genes. Like other zinc uptake regulator (Zur) proteins, Zur represses transcription of its regulon when Zn is replete and binds more weakly to DNA when Zn is limiting. Previous studies established that Zur proteins are homodimeric and harbor at least two metal sites per protomer or four per dimer.

Drosophila melanogaster frataxin: protein crystal and predicted solution structure with identification of the iron-binding regions.

Friedreich's ataxia (FRDA) is a hereditary cardiodegenerative and neurodegenerative disease that affects 1 in 50 000 Americans. FRDA arises from either a cellular inability to produce sufficient quantities or the production of a nonfunctional form of the protein frataxin, a key molecule associated with mitochondrial iron-sulfur cluster biosynthesis. Within the mitochondrial iron-sulfur cluster (ISC) assembly pathway, frataxin serves as an allosteric regulator for cysteine desulfurase, the enzyme that provides sulfur for [2Fe-2S] cluster assembly.

Pb(II) coordination to the nonclassical zinc finger tristetraprolin: retained function with an altered fold.

Tristetraprolin (TTP) is a nonclassical CCCH zinc finger (ZF) that plays a crucial role in regulating inflammation. TTP regulates cytokine mRNAs by specific binding of its two conserved ZF domains (CysXCysXCysXHis) to adenylate-uridylate-rich sequences (AREs) at the 3'-untranslated region, leading to degradation of the RNA. Dysregulation of TTP in animal models has demonstrated several cytokine-related syndromes, including chronic inflammation and autoimmune disorders.

Photocatalytic Hydrogen Evolution by a De Novo Designed Metalloprotein that Undergoes Ni-Mediated Oligomerization Shift.

De novo metalloprotein design involves the construction of proteins guided by specific repeat patterns of polar and apolar residues, which, upon self-assembly, provide a suitable environment to bind metals and produce artificial metalloenzymes. While a wide range of functionalities have been realized in de novo designed metalloproteins, the functional repertoire of such constructs towards alternative energy-relevant catalysis is currently limited. Here we show the application of de novo approach to design a functional H evolving protein.

Characteristics of the Isu1 C-terminus in relation to [2Fe-2S] cluster assembly and ISCU Myopathy.

Mitochondrial [2Fe-2S] cluster biosynthesis is driven by the coordinated activities of the Iron-Sulfur Cluster (ISC) pathway protein machinery. Within the ISC machinery, the protein that provides a structural scaffold on which [2Fe-2S] clusters are assembled is the ISCU protein in humans; this protein is referred to as the "Scaffold" protein. Truncation of the C-terminal portion of ISCU causes the fatal disease "ISCU Myopathy", which exhibits phenotypes of reduced Fe-S cluster assembly in cells.

Molecular characteristics of proteins within the mitochondrial Fe-S cluster assembly complex.

Iron-Sulfur (Fe-S) clusters are essential for life, as they are widely utilized in nearly every biochemical pathway. When bound to proteins, Fe-S clusters assist in catalysis, signal recognition, and energy transfer events, as well as additional cellular pathways including cellular respiration and DNA repair and replication. In Eukaryotes, Fe-S clusters are produced through coordinated activity by mitochondrial Iron-Sulfur Cluster (ISC) assembly pathway proteins through direct assembly, or through the production of the activated sulfur substrate used by the Cytosolic Iron-Sulfur Cluster Assembly (CIA) pathway.

Molecular Details of the Frataxin-Scaffold Interaction during Mitochondrial Fe-S Cluster Assembly.

Iron-sulfur clusters are essential to almost every life form and utilized for their unique structural and redox-targeted activities within cells during many cellular pathways. Although there are three different Fe-S cluster assembly pathways in prokaryotes (the NIF, SUF and ISC pathways) and two in eukaryotes (CIA and ISC pathways), the iron-sulfur cluster (ISC) pathway serves as the central mechanism for providing 2Fe-2S clusters, directly and indirectly, throughout the entire cell in eukaryotes. Proteins central to the eukaryotic ISC cluster assembly complex include the cysteine desulfurase, a cysteine desulfurase accessory protein, the acyl carrier protein, the scaffold protein and frataxin (in humans, FS1, SD11, CP, SCU and XN, respectively).

Evaluation of the Physicochemical Properties of the Iron Nanoparticle Drug Products: Brand and Generic Sodium Ferric Gluconate.

Complex iron nanoparticle-based drugs are one of the oldest and most frequently administered classes of nanomedicines. In the US, there are seven FDA-approved iron nanoparticle reference drug products, of which one also has an approved generic drug product (i.e.

Refinement of protein Fe(II) binding characteristics utilizing a competition assay exploiting small molecule ferrous chelators.

Iron is the most prevalent metal in biology. Its chemical and redox versatility allows it to direct activity of many Fe binding proteins. While iron's biological applications are diverse, challenges inherent in having Fe(II) present at high abundance means cells must ensure delivery to the correct recipient, while also ensuring its chemistry is regulated.

Role of Gold in Inflammation and Tristetraprolin Activity.

The zinc finger protein tristetraprolin (TTP) regulates inflammation by downregulating cytokine mRNAs. Misregulation results in arthritis, sepsis and cancer, and there is an interest in modulating TTP activity with exogenous agents. Gold has anti-inflammatory properties and has recently been shown to modulate the signaling pathway that produces TTP, suggesting that TTP may be a target of gold.

Unique roles of iron and zinc binding to the yeast Fe-S cluster scaffold assembly protein "Isu1".

Mitochondrial Fe-S cluster biosynthesis is accomplished within yeast utilizing the biophysical attributes of the "Isu1" scaffold assembly protein. As a member of a highly homologous protein family, Isu1 has sequence conservation between orthologs and a conserved ability to assemble [2Fe-2S] clusters. Regardless of species, scaffold orthologs have been shown to exist in both "disordered" and "structured" conformations, a structural architecture that is directly related to conformations utilized during Fe-S cluster assembly.

Manganese co-localizes with calcium and phosphorus in acidocalcisomes and is mobilized in manganese-deficient conditions.

Exposing cells to excess metal concentrations well beyond the cellular quota is a powerful tool for understanding the molecular mechanisms of metal homeostasis. Such improved understanding may enable bioengineering of organisms with improved nutrition and bioremediation capacity. We report here that can accumulate manganese (Mn) in proportion to extracellular supply, up to 30-fold greater than its typical quota and with remarkable tolerance.

Backbone resonance assignments and secondary structure of the apo-Drosophila melanogaster frataxin homolog (Dfh).

Friedreich's ataxia, the most prevalent hereditary ataxia, is caused by a patient's inability to produce a viable form of the protein frataxin. Frataxin plays an essential role in cellular iron regulation and has been shown to participate in the assembly of iron-sulfur (Fe-S) clusters under a variety of roles, including modulating persulfide production and directing Fe(II) delivery to the assembly scaffold protein. While the activity and structure of multiple eukaryotic frataxin orthologs have been characterized, the fly ortholog has numerous advantages over other orthologs with regards to protein stability, its activity towards Fe-S cluster assembly and its stability for forming stable proteins partner assemblies.

Simultaneous nitrosylation and N-nitrosation of a Ni-thiolate model complex of Ni-containing SOD.

Nitric oxide (NO) is used as a substrate analogue/spectroscopic probe of metal sites that bind and activate oxygen and its derivatives. To assess the interaction of superoxide with the Ni center in Ni-containing superoxide dismutase (NiSOD), we studied the reaction of NO and NO with the model complex, EtN[Ni(nmp)(SPh--NH--CF)] (; nmp = dianion of -(2-mercaptoethyl)picolinamide; SPh--NH--CF = 2-amino-4-(trifluoromethyl)benzenethiolate) and its oxidized analogue , respectively. The ultimate products of these reactions are the disulfide of SPh--NH--CF and the ,-bridged tetrameric complex [Ni(nmp)], a result of S-based redox activity.

Nanothermometry Reveals Calcium-Induced Remodeling of Myosin.

Ions greatly influence protein structure-function and are critical to health and disease. A 10, 000-fold higher calcium in the sarcoplasmic reticulum (SR) of muscle suggests elevated calcium levels near active calcium channels at the SR membrane and the impact of localized high calcium on the structure-function of the motor protein myosin. In the current study, combined quantum dot (QD)-based nanothermometry and circular dichroism (CD) spectroscopy enabled detection of previously unknown enthalpy changes and associated structural remodeling of myosin, impacting its function following exposure to elevated calcium.

From micelles to bicelles: Effect of the membrane on particulate methane monooxygenase activity.

Particulate methane monooxygenase (pMMO) is a copper-dependent integral membrane metalloenzyme that converts methane to methanol in methanotrophic bacteria. Studies of isolated pMMO have been hindered by loss of enzymatic activity upon its removal from the native membrane. To characterize pMMO in a membrane-like environment, we reconstituted pMMOs from () (Bath) and () 20Z into bicelles.

Cu-specific CopB transporter: Revising P-type ATPase classification.

The copper-transporting P-ATPases, which play a key role in cellular copper homeostasis, have been divided traditionally into two subfamilies, the P-ATPases or CopAs and the P-ATPases or CopBs. CopAs selectively export Cu whereas previous studies and bioinformatic analyses have suggested that CopBs are specific for Cu export. Biochemical and spectroscopic characterization of CopB (CopB) show that, while it does bind Cu, the binding site is not the prototypical P-ATPase transmembrane site and does not involve sulfur coordination as proposed previously.