Zn(II) ions bind very efficiently to tandem repeat region of "prion related protein" (PrP-rel-2) of zebra-fish. MS and potentiometric evidence

Comparing Prion Proteins Across Species: Is Zebrafish a Useful Model?

Despite the considerable body of research dedicated to the field of neurodegeneration, the gap in knowledge on the prion protein and its intricate involvement in brain diseases remains substantial. However, in the past decades, many steps forward have been taken toward a better understanding of the molecular mechanisms underlying both the physiological role of the prion protein and the misfolding event converting it into its pathological counterpart, the prion. This review aims to provide an overview of the main findings regarding this protein, highlighting the advantages of many different animal models that share a conserved amino acid sequence and/or structure with the human prion protein. A particular focus will be given to the species Danio rerio, a compelling research organism for the investigation of prion biology, thanks to its conserved orthologs, ease of genetic manipulation, and cost-effectiveness of high-throughput experimentation. We will explore its potential in filling some of the gaps on physiological and pathological aspects of the prion protein, with the aim of directing the future development of therapeutic interventions.

Investigation of metal interactions with YrpE protein of Bacillus subtilis by a polyhistidine peptide model

The use of model peptides that can simulate the behaviour of a protein domain is a very successful analytical method to study the metal coordination sites in biological systems. Here we study zinc and copper binding ability of the sequence HTHEHSHDHSHAH, which serves as model for the metal interactions with YrpE, a putative metal-binding protein of the ZinT family identified in Bacillus subtilis. Compared to other ZinT proteins secreted by Gram-negative bacteria, the metal-coordination properties of YrpE N-terminal histidine-rich domain have not been yet characterized. Different independent analytical methods, aimed at providing information on the stability and structure of the formed species, have been employed, including potentiometric titrations, electrospray ionization mass spectrometry, UV-Vis spectrophotometry, circular dichroism and electron paramagnetic resonance spectroscopy. The obtained speciation models and equilibrium constants allowed to compare the metal-binding ability of the investigated polyhistidine sequence with that of other well-known histidine-rich peptides. Our thermodynamic results revealed that the YrpE domain HTHEHSHDHSHAH forms more stable metal complexes than other His-rich domains of similar ZinT proteins. Moreover, the studied peptide, containing the alternated (-XH-)n motif, proved to be even more effective than the His6-tag (widely used in immobilized metal ion affinity chromatography) in binding zinc ions.

The Potential Antimicrobial Action of Human Mucin 7 15-Mer Peptide and Its Metal Complexes

Mucin 7 (encoded byMUC7) is a human salivary protein that has a role in the natural immune system. Fragments of mucin 7 exhibit antimicrobial activity against bacteria and yeast. Although the antimicrobial properties of peptides have been known and studied for decades, the exact mechanism of action of antimicrobial peptides (AMPs) is still unclear. It is known that some AMPs require divalent metal ions to activate their activity. Herein, we investigated three 15-mer MUC7 peptides, one of which (mother peptide, sequence, L3) is a synthetic analog of a fragment naturally excised from MUC7 (with His3, His8, and His 14) and its two structural analogs, containing only two histidine residues, His3, His13 and His8, His13 (L2 and L1, respectively). Since there is a correlation between lipophilicity, the presence of metal ions (such as Cu(II) and Zn(II)) and antimicrobial activity of AMP, antimicrobial properties of the studied peptides, as well as their complexes with Cu(II) and Zn(II) ions, were tested for activity against Gram-positive (Enterococcus faecalis, Staphylococcus epidermidis) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria and fungi (Candida albicans). The results were correlated with their lipophilicity. Coordination and thermodynamic studies (potentiometry, UV-Vis, CD) revealed the formation of mainly mononuclear complexes in solution for all studied systems with different stability in the physiological pH range.

Investigation on the metal binding sites of a putative Zn(ii) transporter in opportunistic yeast species Candida albicans

The protein fragment C4YJH2 of Candida albicans has the ability to tightly coordinate Zn(ii) at its C-terminal region by means of an evolutionarily well-conserved histidine-rich sequence.

The unusual metal ion binding ability of histidyl tags and their mutated derivatives

Peptides that consist of repeated sequences of alternating histidines and alanines strongly bind Cu(ii) and form α-helical structures.

African Viper Poly-His Tag Peptide Fragment Efficiently Binds Metal Ions and Is Folded into an α-Helical Structure

Snake venoms are complex mixtures of toxic and often spectacularly biologically active components. Some African vipers contain polyhistidine and polyglycine peptides, which play a crucial role in the interaction with metal ions during the inhibition of snake metalloproteases. Polyhistidine peptide fragments, known as poly-His tags, play many important functions, e.g., in metal ion transport in bacterial chaperon proteins. In this paper, we report a detailed characterization of Cu(2+), Ni(2+), and Zn(2+) complexes with the EDDHHHHHHHHHG peptide fragment (pHG) derived from the venom of the rough scale bush viper (Atheris squamigera). In order to determine the thermodynamic properties, stoichiometry, binding sites, and structures of the metal-pHG complexes, we used a combination of experimental techniques (potentiometric titrations, electrospray ionization mass spectrometry, UV-vis spectroscopy, circular dichroism spectroscopy, and electron paramagnetic resonance spectroscopy) and extensive computational tools (molecular dynamics simulations and density functional theory calculations). The results showed that pHG has a high affinity toward metal ions. The numerous histidine residues located along this sequence are efficient metal ion chelators with high affinities toward Cu(2+), Ni(2+), and Zn(2+) ions. The formation of an α-helical structure induced by metal ion coordination and the occurrence of polymorphic binding states were observed. It is proposed that metal ions can "move along" the poly-His tag, which serves as a metal ion transport pathway. The coordination of Cu(2+), Ni(2+), and Zn(2+) ions to the histidine tag is very effective in comparison with other histidine-rich peptides. The stabilities of the metal-pHG complexes increase in the order Zn(2+) < Ni(2+)≪ Cu(2+).

LIV-1 ZIP ectodomain shedding in prion-infected mice resembles cellular response to transition metal starvation

We recently documented the co-purification of members of the LIV-1 subfamily of ZIP (Zrt-, Irt-like Protein) zinc transporters (LZTs) with the cellular prion protein (PrP(C)) and, subsequently, established that the prion gene family descended from an ancestral LZT gene. Here, we begin to address whether the study of LZTs can shed light on the biology of prion proteins in health and disease. Starting from an observation of an abnormal LZT immunoreactive band in prion-infected mice, subsequent cell biological analyses uncovered a surprisingly coordinated biology of ZIP10 (an LZT member) and prion proteins that involves alterations to N-glycosylation and endoproteolysis in response to manipulations to the extracellular divalent cation milieu. Starving cells of manganese or zinc, but not copper, causes shedding of the N1 fragment of PrP(C) and of the ectodomain of ZIP10. For ZIP10, this posttranslational biology is influenced by an interaction between its PrP-like ectodomain and a conserved metal coordination site within its C-terminal multi-spanning transmembrane domain. The transition metal starvation-induced cleavage of ZIP10 can be differentiated by an immature N-glycosylation signature from a constitutive cleavage targeting the same site. Data from this work provide a first glimpse into a hitherto neglected molecular biology that ties PrP to its LZT cousins and suggest that manganese or zinc starvation may contribute to the etiology of prion disease in mice.

Competition between histamine-like and poly-imidazole coordination sites for Cu(2+) and Zn(2+) ions in zebra-fish peptide of prion-like protein

The fragment of the zebrafish prion-like protein (PrP-rel-2), encompassing residues 74-86 and unprotected at N-terminus (zf74-86) represents a good model to understand Cu(2+) and Zn(2+) binding to ligands containing multi-potential metal donor sites. Zf(74-86) contains four His and His-1 N-terminal amine groups which constitute both copper and zinc anchoring sites. The presence of His at the first position additionally provides the histamine-like binding mode which could compete with the multi-His binding mode. In this study the speciation profiles of the Cu(2+) and Zn(2+) complexes with zf74-86 have been obtained. The main species, dominating at physiological pH, have been fully characterized by using different spectroscopic techniques. The detected NMR chemical shift variations and line broadening enhancements, caused by Zn(2+) and Cu(2+) respectively, allowed to determine the metal binding sites. Both metal ions showed common binding donor atoms, being 2 or 3 His imidazoles and the N-terminal group involved in Cu(2+) and Zn(2+) binding.

Prion proteins and copper ions. Biological and chemical controversies

The Prion protein (PrP(c)) involvement in some neurodegenerative diseases is well assessed although its "normal" biological role is not completely understood. It is known that PrP(C) can bind Cu(II) ions with high specificity but the order of magnitude of the corresponding affinity constant(s) is still highly debated. This perspective is an attempt to collect the current knowledge on these topics and to build up a bridge between the biological and the chemical points of view.

Heteronuclear and homonuclear Cu2+ and Zn2+ complexes with multihistidine peptides based on zebrafish prion-like protein

The homeostasis of metal ions, especially copper and zinc, is a major factor that may influence the prion diseases and the biological function of prion protein (PrP). The His-rich regions are basic sites for metal binding and antioxidant activity of the PrP structures. Animal prion-like proteins contain also His-rich domains, and their coordination chemistry may provide better insight into the chemistry and biology of PrP structures and related diseases. Herein, we report an equilibrium study on heteronuclear Zn(2+)-Cu(2+) complexes with zrel-PrP fragments from zebrafish. Potentiometric, spectroscopic, and mass spectrometric methods showed that the binding of copper is much more effective than the binding of zinc. At physiological pH, both metals bind to the histidine imidazole N donors of the studied peptides.

Evolutionary descent of prion genes from the ZIP family of metal ion transporters

In the more than twenty years since its discovery, both the phylogenetic origin and cellular function of the prion protein (PrP) have remained enigmatic. Insights into a possible function of PrP may be obtained through the characterization of its molecular neighborhood in cells. Quantitative interactome data demonstrated the spatial proximity of two metal ion transporters of the ZIP family, ZIP6 and ZIP10, to mammalian prion proteins in vivo. A subsequent bioinformatic analysis revealed the unexpected presence of a PrP-like amino acid sequence within the N-terminal, extracellular domain of a distinct sub-branch of the ZIP protein family that includes ZIP5, ZIP6 and ZIP10. Additional structural threading and orthologous sequence alignment analyses argued that the prion gene family is phylogenetically derived from a ZIP-like ancestral molecule. The level of sequence homology and the presence of prion protein genes in most chordate species place the split from the ZIP-like ancestor gene at the base of the chordate lineage. This relationship explains structural and functional features found within mammalian prion proteins as elements of an ancient involvement in the transmembrane transport of divalent cations. The phylogenetic and spatial connection to ZIP proteins is expected to open new avenues of research to elucidate the biology of the prion protein in health and disease.

Structural features of the Zn(2+) complex with the single repeat region of "prion related protein" (PrP-rel-2) of zebrafish zPrP63-70 fragment

The interaction between Zn(2+) and the single repeat of PrP-rel-2 of zebrafish at physiological pH was investigated by NMR spectroscopy; the chemical shift mapping and the proton-proton distances were used to obtain the structural model of the Zn(2+) complex.