The Role of Y-PARK9 protein in preventing manganese-induced Parkinson's disease

A variety of metals are essential trace elements but can reach localized toxic concentrations through various disease processes or environmental exposures and have been implicated as having a role in neurodegeneration. In particular, chronic inorganic manganese exposure causes selective toxicity to the nigrostriatal dopaminergic system, resulting in a Parkinsonian-like neurological condition known as Manganism. YPK9 gene (Yeast PARK9; also known as YOR291W) encodes a transmembrane P-type transport ATPase presumably involved in metal coordination and transportation, though its substrate specificity still remains unknown. Mutations in the human homolog of YPK9, PARK9 (ATP13A2), have been linked to genetic forms of early onset parkinsonism. Recently a strong genetic interaction between YPK9 and another Parkinson's disease protein, α-synuclein, has been evidenced in multiple model systems, indicating a crucial role for YPK9 in manganese detoxification in yeast and a specific protecting effect against manganese poisoning [1,3]. With the purpose to shed light on the protective property of YPK9 in Manganese-induced Parkinsonism, we tested the binding ability of Mn(II) and other divalent cations (Cu(II), Zn(II)) towards several peptide sequences from YPK9, with a particular focus on highly conserved sequences from yeast to human. The work was carried out at different pH values and ligand/metal molar ratios by means of potentiometric and spectroscopic techniques (multidimensional and heteronuclear NMR and UV-visible), in order to evaluate and compare the coordination propensity of such fragments with Mn(II) and the other metal probes selected [4,5]

Interaction of divalent cations with protein PARK9

Metals have been shown to play a role in the genesis and development of many neurodegenerative diseases. Park9 encoded protein can protect cells from manganese poisoning, an environmental risk factor for a Parkinson’s disease- like syndrome. Park9 belongs to a family of ATP-ases involved in metal coordination and transportation; familial mutations of this gene may result in early development of PD. We tested two peptide sequences from Park9, -P1D2E3K4H5E6L7- (1) and -F1C2G3D4G5A6N7D8C9G10- (2), for Mn(II), Zn(II) and Cu(II) binding. These fragments are located from 1165 to 1171 and from 1184 to 1193 residues in Park9 sequence, and are highly conserved in a number of organisms, from yeasts to humans. Experiments have been carried out at different pH values and ligand/metal molar ratios with both potentiometric and spectroscopic (NMR, UV-vis) techniques, showing that the three metals are able to effectively bind the examined peptides. Mn(II) and Zn(II) coordination with peptide (1) involves imidazol of His5 and carboxyl γ-O of Asp2, Glu3 and Glu6 residues, in a distorted octahedral geometry, possibly involving bidentate interaction of carboxyl groups; four donor atoms participate in Zn(II) binding, resulting in a tetracoordinated geometry. Mn(II) and Zn(II) coordination involves the two cysteines in peptide (2); Mn(II) accepts additional ligand bonds from D4 and D8 to complete the coordination sphere, together with some water molecules. Details of Cu(II) coordination are under study

The composition of PM1 and PM2.5 samples, metals and their water soluble fractions in the Bologna area (Italy)

Abstract In this study the metal composition of PM 1 and PM 2.5 samples collected in the surroundings of a municipal incinerator located in a suburban–farming area, less than 10 km away from Northeast of Bologna (Italy) was investigated. Seven out of eight monitoring stations were installed in a domain of 8x9 km 2 around the incinerator plant; the eighth station was placed inside the urban area of Bologna. The coordinates of four monitoring stations were selected on the basis of a preliminary study by using a dispersion model. Eleven metals (Al, Sb, As, Cd, Fe, Mn, Ni, Pb, Cu, V, Zn) were quantified in both the filter acid–digests and in the water extracts. The PM 2.5 collected in all the sites of the domain were highly correlated with exception of the urban site. The daily average metal concentrations in summer were 1.84% and 1.14% for PM 2.5 and PM 1 respectively, indicating that fine particles are less enriched in metals. Fe, Al and Zn were the most abundant elements, and they represented about the 80% of the total amount of the analyzed ones. The average water soluble metal compositions were 0.71% and 0.41% for PM 2.5 and PM 1 respectively. In the sites of the suburban–farming studied area the Principal Component Analysis (PCA) and Cluster Analysis revealed differences between water soluble metal compositions in PM 1 and PM 2.5 . The urban sites were characterized by lower total and soluble metals contents than the other PM 2.5 stations installed around the incinerator plant. However, no noticeable difference in the concentrations of metals in the particulate matter between the sites chosen as maxima of incinerator emissions and the control sites was observed

unexpected impact of the number of glutamine residues on metal complex stability

The emerging question which this study aims to answer is: what impact do glutamines have on the stability of metal–peptide complexes? We focused our attention on the N-terminal domain of Hpn and Hpn-like proteins from Helicobacter pylori. Cu2+ and Ni2+ complexes of the model peptides MAHHE-NH2, MAHHEEQ-NH2, MAHHEQQ-NH2 and MAHHEQQHQA-NH2 were studied by means of different thermodynamic and spectroscopic techniques, as well as through molecular modelling computation. Experimental results, in very good agreement with theoretical findings, lead to the not obvious conclusion that the stability of metal complexes distinctly increases with the number of glutamine residues present in the peptide, although glutamine side-chains do not directly take part in coordination. This peculiar finding allows one to look at polyglutamine sequences, not only the ones present in some bacterial chaperones but also those involved in several neurodegenerative diseases, from a new perspective

Metallacrowns of Ni(II) with alpha-aminohydroxamic acids in aqueous solution: beyond a 12-MC-4, an unexpected (vacant?) 15-MC-5

Growing attention has been devoted in the recent years to a class of metallamacrocycles known as metallacrowns (MCs). They are structural analogues of crown ethers where the methylene bridges have been substituted by coordinative bonds formed by a transition metal ion ("ring" metal) and a nitrogen atom. The cavity of the metallacrown can accommodate an additional metal ion ("core" metal) either identical or different from the ring metal, thus forming a homo- or hetero-metallic MC. The most studied ring metal ion is certainly Cu(2+) and the aminohydroxamic acids have proved to be very suitable ligands to form MCs. The behavioural analogies between Cu(2+) and Ni(2+) in forming complexes, along with recent literature data in the solid state, prompted us to investigate the possible MC formation between Ni(2+) and both (S)-α-alaninehydroxamic acid and (S)-valinehydroxamic acid, in aqueous solution. Two metallacrowns, a 12-MC-4 and an unexpected 15-MC-5 have been detected by potentiometry and confirmed by ESI-MS results. Their structures are discussed on the basis of potentiometric, calorimetric, spectroscopic data and DFT calculations. The existence of a vacant 15-MC-5 species in solution can be put forward for the first time, making the present metal/ligand systems very interesting for their potential applications in cation recognition and separation. Finally, the crystal structure of the binary complex K[NiL(2)H(-1)]·5/3 H(2)O of (S)-α-alaninehydroxamic acid (LH) is also reported

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

Interaction of divalent cations with Park9 protein fragments

Two peptide sequences from Park9 Parkinson’s disease (PD) gene, -P1D2E3K4H5E6L7- (1) and -F1C2G3D4G5A6N7D8C9G10- (2) have been tested for Mn(II), Zn(II) and Cu(II) binding. Park9 encoded protein can protect cells from manganese poisoning, which is an environmental risk factor for a Parkinson’s disease-like syndrome [1-4]. In fact, Park9 belongs to a family of ATP-ases involved in metal coordination and transportation; familial gene mutations may result in early development of PD. The chosen fragments are located from 1165 to 1171 and from 1184 to 1193 residues in the Park9 sequence, and are highly conserved in a number of organisms, going from yeasts to humans. Potentiometric, UV-vis experiments together with mono- and multidimensional NMR spectroscopy have been used to understand the details of metal binding sites at different pH values and at different ligand to metal molar ratios, showing that the three metals are able to effectively bind the examined peptides. From NMR measurements Mn(II) and Zn(II) coordination with peptide 1 involves imidazole Nε or Nδ of His5 and carboxyl γ-O of Asp2, Glu3 and Glu6 residues. Six donor atoms participate in Mn(II) binding, resulting in a distorted octahedral geometry, possibly involving bidentate interaction of carboxyl groups; four donor atoms participate in Zn(II) binding, resulting in a tetracoordinated geometry. Potentiometric data show that soluble, hydroxylated Zn(II) species are formed in the alkaline pH range. The formation of Cu(II) complexes with peptide 1 starts below pH: only mononuclear complexes have been potentiometrically detected also in the presence of excess of ligand. Imidazole nitrogen of His residues acts as first Cu(II) anchoring site; as pH is raised, ligand coordination proceeds with deprotonation and binding of neighbouring amide nitrogens of the peptidic backbone. UV-vis spectra agree that the main species at neutral pH is a {Nim, 2N-, O} complex, where the oxygen atom most likely belongs to an equatorially coordinated water molecule. Cu(II), Mn(II) and Zn(II) coordination involves the cysteine residues with peptide 2 and complex-formation invariably starts at lower pH with respect to ligand 1. Mn(II) accepts additional ligand bonds from D4 and D8 to complete the coordination sphere; the unoccupied sites may contain solvent molecules. When the ligand is in excess, both Zn(II) and Cu(II) ions form bis-complexes. The two metal ions behave in a very similar way and the stoichiometry of main species at physiological pH depends on the metal/ligand ratio: [ML]2- in equimolar solution or [MHL2]5- for the 1:2 ratio. Potentiometric data suggest for the former a {2S, 2O} and for the latter a {3S, 1O} coordination without any participation of amide nitrogens, as usually found for Cu(II)/peptide complexes

Park9 interaction with Manganese and other divalent cations

Two peptide sequences from Park9 Parkinson’s disease gene, P1D2E3K4H5E6L7 (1) and F1C2G3D4G5A6N7D8C9G10 (2) have been studied in their interaction with Mn(II) and Zn(II) ions. These fragments lie from residue 1165 to 1171 and from 1184 to 1193 in the Park9 encoded protein, that can protect cells from manganese poisoning, an environmental risk factor for a Parkinson’s disease-like syndrome called Manganism. The study was carried out through potentiometric and spectroscopic (UV-Vis, EPR, mono- and multidimensional NMR) techniques, to cast light on the details of metal binding at different pH values and different ligand to metal molar ratios

Chiral Ligand-Exchange Chromatography of Pharmaceutical Compounds on Dinamically Coated (Home-Made) Stationary Phases

It is well known for several decades that the two enantiomeric forms of a chiral compound can have very different effects on the human body. For this reason the synthesis or extraction from a natural source of a potential new drug, as well as its marketing, require a careful control of its optical purity. Chromatographic techniques can respond extremely well to this need, both in the analytical and in the preparative field. Among the several methods developed for this purpose, one of the first and of the most effective is the Chiral Ligand-Exchange Chromatography, which is based on the stability difference between the metallic diastereomeric complexes containing one or the other of the two enantiomers to be separated and a suitable chiral selector. This technique has been effectively used for resolving racemic mixtures of products of biomedical and/or pharmacological interest, such as α- and β-amino acids either proteinogenic or non-proteinogenic, oligopeptides, amino alcohols or beta-blockers. All these substances are linked together by their ability to bind metal ions, the most widely used of which is Cu(II). The chiral selector can be a component of either the mobile or the stationary phase, to which it can be either chemically bonded or dynamically adsorbed. The latter method has several advantages of convenience and, above all, cheapness. The preparation of dynamically-coated chiral stationary phases for Ligand-Exchange Chromatography has produced a large number of applications, the main of which, both in TLC and in HPLC, are reviewed below