Interaction of Cu(II) and Ni(II) with Park9 Protein fragments via NMR Studies

Massimiliano Peana;Serenella Medici;Alessia Ledda;NURCHI, VALERIA MARINA;Maria Antonietta Zoroddu

2014-01-01

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Abstract

A fragment of Ypk9 protein, P1D2E3K4H5E6L7 (PK9-H), was studied for its coordination abilities towards Ni(II) and Cu(II) ions through mono- and bidimensional NMR techniques. Park9 belongs to the P5-type ATPase family; its mutation is able to induce a juvenile form of Parkinsonism in humans, and seems to be connected to manganese poisoning in both yeasts and humans. For this reason, some significant sequences of Park9 and the yeast homologue Ypk9 have been already investigated forMn(II) binding. The proteins belong to an ATPase (P5 type) family involved in the transportation of metal ions, including manganese and nickel, from the cytosol to the lysosomal lumen. Here, we tested PK9-H with Cu(II) and Ni(II) ions; the former because it is an essential element ubiquitous in the human body, so its trafficking should be strictly regulated and one cannot exclude that Ypk9 may play a role in it, and the latter because, besides being a toxic element for many organisms and being involved in different pathologies and inflammation states, it seems that the protein confers protection against it. Furthermore, nickel ions in the proper coordination geometry could be a good diamagnetic probe for metal binding. NMR experiments showed that both cations can bind PK9-H in an effective way, leading to complexes whose coordination mode depends on the pH of the solution. NMR data have been used to build a model for the structure of the major Cu(II) and Ni(II) complexes. Structural changes in the conformation of the peptide with organized side chain orientation promoted by nickel coordination were detected.