A comparative study on the possible zinc binding sites of the human ZnT3 zinc transporter protein

作者：Arus David; Dancs Agnes; Nagy Nora Veronika; Gajda Tamas^*

来源：Dalton Transactions, 2013, 42(33): 12031-12040.

DOI：10.1039/c3dt50754h

The brain specific zinc transporter protein ZnT3 can be related to the amyloid neuropathology of Alzheimer%26apos;s disease. In order to analyze the metal binding ability of human ZnT3 protein, here we report a potentiometric and solution structural (UV-Vis, CD, EPR, NMR) study of nickel(II), copper(II) and zinc(II) complexes of three peptides mimicking the possible metal binding sequences of this protein. The peptide L-1 (Ac-RHQAGPPHSHR-NH2) is a minimalist, the cyclic peptide L-2 (cyclo(Ac-CKLHQAGPPHSHGSR-GAEYAPLEEGPEEKC-NH2) is a more complete model of the intracellular His-rich loop, which is widely accepted as a putative metal binding site. The peptide L-3 (Ac-PFHHCHRD-NH2) is the model of the conserved cytoplasmic N-terminal -HHCH-sequence. In the physiological pH-range, the ZnL1, ZnH3L2 and ZnL3 complexes are the major species in the corresponding binary systems, with {3N(im)}, {3N(im), 2/3O(amide)} and {3N(im), S-} coordination environments, respectively. The species ZnL3 has 3-4 orders of magnitude higher stability than the other two complexes, indicating the presence of a high-affinity zinc-binding site at the N-terminal tail of the human ZnT3 transporter. Moreover, L-3 shows preferred zinc binding as compared to nickel (log beta(ZnL3) - log beta(NiL3) = 2.3), probably due to the higher preference of zinc(II) for tetrahedral geometry. These facts suggest that zinc binding to the N-terminal -HHCH-sequence of human ZnT3 may be involved in the biological activity of this zinc transporter protein in zinc sensing, binding or translocation processes.

• 出版日期2013