The Angiotensin Metabolite His-Leu Is a Strong Copper Chelator Forming Highly Redox Active Species.

His-Leu is a hydrolytic byproduct of angiotensin metabolism, whose concentration in the bloodstream could be at least micromolar. This encouraged us to investigate its Cu(II) binding properties and the concomitant redox reactivity. The Cu(II) binding constants were derived from isothermal titration calorimetry and potentiometry, while identities and structures of complexes were obtained from ultraviolet-visible, circular dichroism, and room-temperature electronic paramagnetic resonance spectroscopies.

Nobody's Perfect: Choice of the Buffer and the Rate of Cu Ion-Peptide Interaction.

The choice of correct pH buffer is crucial in chemical studies modeling biological processes involving Cu ions. Popular buffers for physiological pH are known to form Cu(II) complexes, but their impact on kinetics of Cu(II) complexation has not been considered. We performed a stopped-flow kinetic study of Cu ion interactions with four popular buffers (phosphate, Tris, HEPES, and MOPS) and two buffers considered as nonbinding (MES and PIPPS).

Copper interaction with cystatin C: effects on protein structure and oligomerization.

Human cystatin C (hCC), a small secretory protein, has gained attention beyond its classical role as a cysteine protease inhibitor owing to its potential involvement in neurodegenerative disorders. This study investigates the interaction between copper(II) ions [Cu(II)] and hCC, specifically targeting histidine residues known to participate in metal binding. Through various analytical techniques, including mutagenesis, circular dichroism, fluorescence assays, gel filtration chromatography, and electron microscopy, we evaluated the impact of Cu(II) ions on the structure and oligomerization of hCC.

Exploring the inhibitory potential of -designed small peptides on Hp0231 (DsbK), a periplasmic oxidoreductase involved in disulfide bond formation.

is a bacterium that colonizes the gastric epithelium, which affects millions of people worldwide. infection can lead to various gastrointestinal diseases, including gastric adenocarcinoma and mucosa-associated lymphoid tissue lymphoma. Conventional antibiotic therapies face challenges due to increasing antibiotic resistance and patient non-compliance, necessitating the exploration of alternative treatment approaches.

The Cu(II) affinity constant and reactivity of Hepcidin-25, the main iron regulator in human blood.

Hepcidin is an iron regulatory hormone that does not bind iron directly. Instead, its mature 25-peptide form (H25) contains a binding site for other metals, the so-called ATCUN/NTS (amino-terminal Cu/Ni binding site). The Cu(II)-hepcidin complex was previously studied, but due to poor solubility and difficult handling of the peptide the definitive account on the binding equilibrium was not obtained reliably.

Zn(II) to Ag(I) Swap in Rad50 Zinc Hook Domain Leads to Interprotein Complex Disruption through the Formation of Highly Stable Ag(Cys) Cores.

The widespread application of silver nanoparticles in medicinal and daily life products increases the exposure to Ag(I) of thiol-rich biological environments, which help control the cellular metallome. A displacement of native metal cofactors from their cognate protein sites is a known phenomenon for carcinogenic and otherwise toxic metal ions. Here, we examined the interaction of Ag(I) with the peptide model of the interprotein zinc hook (Hk) domain of Rad50 protein from , a key player in DNA double-strand break (DSB) repair.

Reactive Cu2+-peptide intermediates revealed by kinetic studies gain relevance by matching time windows in copper metallomics.

The purpose of this essay is to propose that metallomic studies in the area of extracellular copper transport are incomplete without the explicit consideration of kinetics of Cu2+ion binding and exchange reactions. The kinetic data should be interpreted in the context of time constraints imposed by specific physiological processes. Examples from experimental studies of Cu2+ ion interactions with amino-terminal copper and nickel binding site/N-terminal site motifs are used to demonstrate that duration and periodicity of such processes as bloodstream transport or neurotransmission promote the reaction intermediates to the role of physiological effectors.

Corrigendum: Ni-assisted hydrolysis may affect the human proteome; filaggrin degradation as an example of possible consequences.

[This corrects the article DOI: 10.3389/fmolb.2022.

An Overlooked Hepcidin-Cadmium Connection.

Hepcidin (DTHFPICIFCCGCCHRSKCGMCCKT), an iron-regulatory hormone, is a 25-amino-acid peptide with four intramolecular disulfide bonds circulating in blood. Its hormonal activity is indirect and consists of marking ferroportin-1 (an iron exporter) for degradation. Hepcidin biosynthesis involves the N-terminally extended precursors prepro-hepcidin and pro-hepcidin, processed by peptidases to the final 25-peptide form.

The rates of Cu(II)-ATCUN complex formation. Why so slow?

We used a series of modified/substituted GGH analogues to investigate the kinetics of Cu(II) binding to ACTUN peptides. Rules for rate modulation by 1 and 2 sphere interactions were established, providing crucial insight into elucidation of the reaction mechanism and its contribution to biological copper transport.

Dual mode of voltammetric studies on Cu(II) complexes of His2 peptides: phosphate and peptide sequence recognition.

Copper(II) complexes of peptides with a histidine residue at the second position (His2 peptides) provide a unique profile of electrochemical behavior, offering signals of both Cu(II) reduction and Cu(II) oxidation. Furthermore, their structures with vacant positions in the equatorial coordination plane could facilitate interactions with other biomolecules. In this work, we designed a library of His2 peptides based on the sequence of Aβ (RHDSG), an amyloid beta peptide derivative.

Ni(II) Ions May Target the Entire Melatonin Biosynthesis Pathway-A Plausible Mechanism of Nickel Toxicity.

Nickel is toxic to humans. Its compounds are carcinogenic. Furthermore, nickel allergy is a severe health problem that affects approximately 10-20% of humans.

Interactions of neurokinin B with copper(II) ions and their potential biological consequences.

Preeclampsia is a blood pressure disorder associated with significant proteinuria. Hypertensive women have increased levels of neurokinin B (NKB) and Cu(II) ions in blood plasma during pregnancy. NKB bears the ATCUN/NTS N-terminal motif empowering strong Cu(II) binding in a characteristic four-nitrogen (4N) square-planar motif, but an alternative Cu(II)NKB geometry was proposed earlier.

Ni-Assisted Hydrolysis May Affect the Human Proteome; Filaggrin Degradation as an Example of Possible Consequences.

Deficiency in a principal epidermal barrier protein, filaggrin (FLG), is associated with multiple allergic manifestations, including atopic dermatitis and contact allergy to nickel. Toxicity caused by dermal and respiratory exposures of the general population to nickel-containing objects and particles is a deleterious side effect of modern technologies. Its molecular mechanism may include the peptide bond hydrolysis in X-S/T-c/p-H-c-X motifs by released Ni ions.

Covalent Proximity Scanning of a Distal Cysteine to Target PI3Kα.

Covalent protein kinase inhibitors exploit currently noncatalytic cysteines in the adenosine 5'-triphosphate (ATP)-binding site via electrophiles directly appended to a reversible-inhibitor scaffold. Here, we delineate a path to target solvent-exposed cysteines at a distance >10 Å from an ATP-site-directed core module and produce potent covalent phosphoinositide 3-kinase α (PI3Kα) inhibitors. First, reactive warheads are used to reach out to Cys862 on PI3Kα, and second, enones are replaced with druglike warheads while linkers are optimized.

Structures of Silver Fingers and a Pathway to Their Genotoxicity.

Recently, we demonstrated that Ag can directly replace Zn in zinc fingers (ZFs). The cooperative binding of Ag to ZFs leads to a thermodynamically irreversible formation of silver clusters destroying the native ZF structure. Thus, a reported loss of biological function of ZF proteins is a likely consequence of such replacement.

Evidence for a Long-Lived, Cu-Coupled and Oxygen-Inert Disulfide Radical Anion in the Assembly of Metallothionein-3 Cu(I)-Thiolate Cluster.

The human copper-binding protein metallothionein-3 (MT-3) can reduce Cu(II) to Cu(I) and form a polynuclear Cu(I)-Cys cluster concomitant with intramolecular disulfide bonds formation, but the cluster is unusually inert toward O and redox-cycling. We utilized a combined array of rapid-mixing spectroscopic techniques to identify and characterize the transient radical intermediates formed in the reaction between ZnMT-3 and Cu(II) to form Cu(I)Zn(II)MT-3. Stopped-flow electronic absorption spectroscopy reveals the rapid formation of transient species with absorption centered at 430-450 nm and consistent with the generation of disulfide radical anions (DRAs) upon reduction of Cu(II) by MT-3 cysteine thiolates.

Tuning Receptor Properties of Metal-Amyloid Beta Complexes. Studies on the Interaction between Ni(II)-Aβ and Phosphates/Nucleotides.

Amyloid-beta (Aβ) peptides, potentially relevant in the pathology of Alzheimer's disease, possess distinctive coordination properties, enabling an effective binding of transition-metal ions, with a preference for Cu(II). In this work, we found that a N-truncated Aβ analogue bearing a His-2 motif, Aβ, forms a stable Ni(II) high-spin octahedral complex at a physiological pH of 7.4 with labile coordination sites and facilitates ternary interactions with phosphates and nucleotides.

Kinetics of Cu(II) complexation by ATCUN/NTS and related peptides: a gold mine of novel ideas for copper biology.

Cu(II)-peptide complexes are intensely studied as models for biological peptides and proteins and for their direct importance in copper homeostasis and dyshomeostasis in human diseases. In particular, high-affinity ATCUN/NTS (amino-terminal copper and nickel/N-terminal site) motifs present in proteins and peptides are considered as Cu(II) transport agents for copper delivery to cells. The information on the affinities and structures of such complexes derived from steady-state methods appears to be insufficient to resolve the mechanisms of copper trafficking, while kinetic studies have recently shown promise in explaining them.

Intermediate Cu(II)-Thiolate Species in the Reduction of Cu(II)GHK by Glutathione: A Handy Chelate for Biological Cu(II) Reduction.

Gly-His-Lys (GHK) is a tripeptide present in the human bloodstream that exhibits a number of biological functions. Its activity is attributed to the copper-complexed form, Cu(II)GHK. Little is known, however, about the molecular aspects of the mechanism of its action.

Electrospray-Induced Mass Spectrometry Is Not Suitable for Determination of Peptidic Cu(II) Complexes.

The toolset of mass spectrometry (MS) is still expanding, and the number of metal ion complexes researched this way is growing. The Cu(II) ion forms particularly strong peptide complexes of biological interest which are frequent objects of MS studies, but quantitative aspects of some reported results are at odds with those of experiments performed in solution. Cu(II) complexes are usually characterized by fast ligand exchange rates, despite their high affinity, and we speculated that such kinetic lability could be responsible for the observed discrepancies.

Ternary Cu Complexes of Human Serum Albumin and Glycyl-l-histidyl-l-lysine.

Human serum albumin (HSA) and the growth factor glycyl-l-histidyl-l-lysine (GHK) bind Cu as part of their normal functions. GHK is found at its highest concentration in the albumin-rich fraction of plasma, leading to speculation that HSA and GHK form a ternary Cu complex. Although preliminary evidence was presented 40 years ago, the structure and stability of such a complex have remained elusive.

Incorporation of β-Alanine in Cu(II) ATCUN Peptide Complexes Increases ROS Levels, DNA Cleavage and Antiproliferative Activity.

Redox-active Cu(II) complexes are able to form reactive oxygen species (ROS) in the presence of oxygen and reducing agents. Recently, Faller et al. reported that ROS generation by Cu(II) ATCUN complexes is not as high as assumed for decades.