Metallomics最新文献

Corynebacteria are commercially and medically important Gram-positive bacteria that can switch from aerobic to anaerobic respiration in response to low O2 and the availability of nitrate as an alternative electron acceptor. The narKGHJI operon encoding the respiratory nitrate reductase is under the control of a novel regulator, ArnR, which plays a major role in the aerobic/anaerobic respiratory switch. ArnR was previously shown to be an iron-sulfur cluster protein that modulates its DNA binding according to availability of O2. However, previous data suggest that it does not do this directly in response to O2, but instead by sensing nitric oxide (NO), which builds up only under low O2 through the activity of nitrate reductase. Here, we report spectroscopic and mass spectrometric studies of C. glutamicum ArnR and its reactions with O2 and NO. We demonstrate that ArnR is a dimer that binds a [4Fe-4S] cluster in each subunit, and this form of the protein binds tightly to DNA. The [4Fe-4S] cluster of AnrR degrades only very slowly in the presence of O2, consistent with the ability of ArnR to repress nar transcription under aerobic conditions. Reaction with NO results in the formation of mono- and di-nitrosylated forms of the [4Fe-4S] ArnR dimer, which exhibit altered DNA-binding characteristics such that the di-nitrosyl form no longer binds to promoter DNA (i.e. cluster degradation is not required in order to modulate DNA binding). These data are consistent with previous literature and lead us to propose a model for AnrR regulatory function.

Ferroptosis, a recently discovered iron-dependent regulated form of cell death, is characterised by lipid peroxidation and oxidative stress. Recent studies suggested that ferroptosis plays a pivotal role in the pathogenesis of chronic obstructive pulmonary disease (COPD), a progressive and irreversible lung disorder, marked by airflow limitation, emphysema, and chronic bronchitis. Cigarette smoke (CS), one of the prominent risk factors for COPD, is known to induce ferroptosis by generating reactive oxygen species (ROS), depleting antioxidant defences, such as glutathione and glutathione peroxidase 4, and disrupting iron homeostasis. These molecular disturbances lead to cell damage, alveolar destruction, and vascular dysfunction, contributing to disease progression and exacerbations. Ferroptosis is also linked with key COPD mechanisms, which are responsible for mitochondrial dysfunction, inflammation, pulmonary hypertension, and CS-induced irregular distribution of iron-binding proteins. A promising therapeutic strategy for mitigating COPD pathogenesis is targeting ferroptosis via iron chelators, lipid peroxide inhibitors, and antioxidant upregulation. Understanding the regulatory mechanisms governing ferroptosis in lung tissue damage could help identify novel biomarkers and effective treatment strategies. This review explores the mechanistic role of ferroptosis in COPD and uncovers the potential intervention methods that may improve clinical outcomes.

Characterization of serum metal element concentrations in pregnancy enables the elucidation of relationships with maternal-fetal and neonatal health. Metal elements in the blood serve as essential cofactors for enzymatic reactions and contribute to blood gas homeostasis, hormone synthesis, and physiological immune function for mother and fetus. Sub-optimal concentrations of some metals have been linked to adverse outcomes, including preterm birth, low birth weight, and impaired neurodevelopment. Maternal obesity also adversely influences metabolic status, including metal metabolism, with the potential for a heightened risk of complications at delivery and long-term health issues in offspring. Research on metal element levels in pregnant women with obesity and their effects on pregnancy outcomes is however limited. This study aims to characterize mid-gestation serum concentrations of 18 metal elements in samples from 755 pregnant women with obesity enrolled in the UK Pregnancies Better Eating and Activity Trial (UPBEAT) and identify associations with pregnancy outcomes. We found that calcium concentration tended to decrease with increasing parity, with an estimated reduction of 6.03 mg/L in multiparous participants compared to nulliparous participants (95% CI: -9.50 to -2.57 mg/L, P = 0.001). Additionally, elevated manganese concentrations at mid-pregnancy were associated with an increased incidence of antepartum haemorrhage after 34 weeks (OR: 4.62, 95% CI: 2.06-12.4, P < 0.001), and higher maternal phosphorus levels were linked to neonatal intensive care unit admissions (OR: 2.83, 95% CI: 1.75-4.67, P < 0.001). A future focus on dysregulation of these metal elements is needed to improve understanding of the clinical associations observed.

Zinc is central to the function of many proteins, yet the mechanisms of zinc homeostasis and their interplay with other cellular systems remain underexplored. In this study, we employ data-dependent acquisition (DDA) and data-independent acquisition (DIA) mass spectrometry to investigate proteome changes in Pseudomonas aeruginosa under conditions of different zinc availability. Using both methods, we detected a combined 2143 unique proteins, 1578 of which were identified by both DDA and DIA. We demonstrated that most of the previously described Zn homeostasis systems exhibit proteomic responses that follow similar trends to those seen in transcriptomics studies. Furthermore, changes in abundance of multiple Zn-metalloproteins and Zn-independent homologs were clearly observable, with respective increases and decreases when Zn was provided, though the magnitude of these changes varied. Most of the Zn-metalloproteins observed were located in one of two Zur-regulated operons between PA5534 and PA5541. This study provides a view of Zn homeostasis mechanisms that is complementary to existing transcriptomics investigations: as gene transcripts are not strictly proportional to the actual distribution of proteins within a cell, analysis of the proteome offers another way to assess the relative use and importance of similar or ostensibly redundant systems in different conditions and can highlight shifts in metal prioritization between metalloproteins.

Zinc(II) ions play manifold roles in human health; dysregulation of zinc homeostasis has been implicated in a number of diseases and pathological conditions. Because zinc(II) is spectroscopically silent, it cannot be detected directly by conventional fluorescence microscopy. As a result, investigators seeking to image zinc(II) in biological systems frequently turn to small-molecule fluorescent sensors that selectively respond to the presence of the ion. This tutorial review describes methods for delivering such small-molecule probes to discrete subcellular locales. Attention is given to the preparation of conjugates in which well-characterized sensors are tethered to molecular homing moieties that accumulate in particular organelles or other compartments. Hybrid approaches that entail enzyme-mediated localization of synthetic constructs, as well as other novel techniques, are also discussed. The various fluorescent probe targeting methods described here enable opportunities for new discoveries in zinc biology.

Metals in circulation and urine had been implicated in atherosclerosis progression, but spatial distribution of metals within plaques and their association with plaque stability remained unclear. This study aimed to clarify differences of metal deposition between symptomatic and asymptomatic carotid plaques and metal spatial distribution within atherosclerotic plaques. We enrolled 15 asymptomatic and 53 symptomatic atherosclerotic plaque specimens during carotid endarterectomy. Each plaque was divided into the plaque core and thickened intimal area. We analyzed the difference of metals within plaques between symptomatic and asymptomatic groups and correlations between age and metal deposition. Besides, 12 additional symptomatic atherosclerotic plaques were used to map metal element distribution by laser ablation inductively coupled plasma mass spectrometry to analyze relative abundance of metal across pathological characteristics of plaques. Significantly higher levels of vanadium, iron, copper, molybdenum, and cadmium were found in the core area of symptomatic plaques compared to asymptomatic plaques, while no difference was observed in plaque thickened intimal area. Copper and lead deposition in core region of symptomatic plaques significantly increased with age. Spatial mapping indicated distinct metal distribution patterns: copper was primarily localized in necrotic and calcified regions, iron was in intraplaque hemorrhage, and calcium and zinc were in calcified areas. Elevated metal accumulation and distinct spatial distribution of metal elements within atherosclerotic plaques might contribute to plaque instability. Our findings highlighted the potential role of metal elements in plaque progression and value of spatial localization methods in studying the pathological roles of metal elements.

Iron-sulfur (Fe-S) clusters are ancient and versatile cofactors that drive essential cellular functions, from electron transport to enzyme catalysis. Their intrinsic sensitivity to oxidation has shaped the evolution of specialized Fe-S cluster biosynthetic and protective mechanisms. Recent findings highlight how human Fe-S-binding regulators exploit this cofactor's reactivity to sense iron and oxygen levels, translating environmental cues into appropriate homeostatic responses. Yet, the same redox sensitivity also renders Fe-S cluster proteins and biosynthesis particularly vulnerable to high oxygen tensions, contributing to pathological outcomes. In this minireview, we examine key discoveries illustrating how Fe-S clusters and oxygen intersect to influence both human health and disease. Finally, we discuss how identifying novel Fe-S targets and regulatory circuits may open innovative therapeutic avenues-harnessing oxygen itself as a strategic element in managing relevant disorders.

Pseudomonas aeruginosa is a major contributor to human infections and is widely distributed in the environment. Its ability for growth under aerobic and anaerobic conditions provides adaptability to environmental changes and in confronting immune responses. We applied native 2-dimensional metalloproteomics to P. aeruginosa to examine how use of iron within the metallome responds to oxic and anoxic conditions. Analyses revealed four iron peaks comprised of metalloproteins with synergistic functions, including (1) respiratory and metabolic enzymes, (2) oxidative stress response enzymes, (3) DNA synthesis and nitrogen assimilation enzymes, and (4) denitrification enzymes and related copper enzymes. Fe Peaks were larger under anoxic conditions, consistent with increased iron demand due to anaerobic metabolism and with the denitrification peak absent under oxic conditions. Three ferritins co-eluted with the first and third iron peaks, localizing iron storage with these functions. Several enzymes were more abundant at low oxygen, including alkylhydroperoxide reductase C that deactivates organic radicals produced by denitrification, all three classes of ribonucleotide reductases (including monomer and oligomer forms), ferritin (increasing in ratio relative to bacterioferritin), and denitrification enzymes. Superoxide dismutase and homogentisate 1,2-dioxygenase were more abundant at high oxygen. Several Fe Peaks contained iron metalloproteins that co-eluted earlier than their predicted size, implying additional protein-protein interactions and suggestive of cellular organization that contributes to iron prioritization in Pseudomonas with its large genome and flexible metabolism. This study characterized the iron metalloproteome of one of the more complex prokaryotic microorganisms, attributing enhanced iron use under anaerobic denitrifying metabolism to its specific metalloprotein constituents.

Iron dyshomeostasis in neurons, involving iron accumulation and abnormal redox balance, is implicated in neurodegeneration. In particular, labile iron, a highly reactive pool of intracellular iron, plays a prominent role in iron-induced neurological damage. However, the mechanisms governing the detoxification and transport of labile iron within neurons are not fully understood. This study investigates the storage and transport of labile ferrous iron Fe(II) in cultured primary rat hippocampal neurons. Iron distribution was studied using live cell fluorescence microscopy with a selective labile Fe(II) fluorescent dye, and synchrotron X-ray fluorescence microscopy (SXRF) for total iron distribution. Fluorescent labeling of the axon initial segment and of lysosomes allowed iron distribution to be correlated with these subcellular compartments. The results show that labile Fe(II) is stored in lysosomes within somas, axons, and dendrites and that lysosomal labile Fe(II) is transported retrogradely and anterogradely along axons and dendrites. In addition, SXRF imaging of total iron confirms iron uptake and iron distribution in the form of iron-rich dots in the soma and neurites. These results suggest that after exposure to Fe(II), labile Fe(II) is stored in lysosomes and can be transported along dendrites and axons. These storage and transport mechanisms could be associated with the detoxification of reactive Fe(II) in lysosomes, which protects cellular structures from oxidative stress. They could also be associated with the metabolic functions of iron in the soma, axons, and dendrites. In this case, easily exchangeable Fe(II) is transported in lysosomes to the neuronal compartments where iron is required.

Six Hyp (A through F) proteins synthesize the NiFe(CN)2CO cofactor found in all [NiFe]-hydrogenases. The Fe(CN)2CO moiety of this cofactor is assembled on a separate scaffold complex comprising HypC and HypD. HypE and HypF generate the cyanide ligands from carbamoyl phosphate by converting the carbamoyl moiety to a thiocyanate associated with HypE's C-terminal cysteine residue, within a conserved 'PRIC' motif. Here, we identify amino acid residue D98 in the central cleft of HypD to be required for biosynthesis of the Fe(CN)2CO moiety and for optimal interaction of HypD with HypE. Construction of a D98A amino acid variant of HypD caused near-complete loss of hydrogenase activity in anaerobically grown Escherichia coli cells, while exchange of the structurally proximal, but non-conserved, residue S356 on HypD, did not. Native mass spectrometric analysis of the anaerobically purified HypC-HypDD98A scaffold complex revealed only a low amount of the bound Fe(CN)2CO group. Western blotting experiments revealed that purified scaffold complexes between either HypC or HybG (a paralogue of HypC) with HypD-D98A showed a strongly impaired interaction with HypE. Examination of the HypCDE complex crystal structure from Thermococcus kodakarensis revealed that D98 of HypD lies within a cleft through which the C-terminus of HypE can access the bound iron ion on HypCD. Alphafold3 predictions suggest that the D98 residue interacts with the arginine residue of the 'PRIC' motif at the C-terminus of HypE to position the modified terminal cysteine residue precisely for delivery of cyanide to the iron ion associated with the HypCD complex.