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The zinc binding loop domain of the HypA protein of Helicobacter pylori consists of two CXXC motifs with flanking His residues. These motifs bind metal ions, and thus they are crucial for the functioning of the whole protein. The N-terminal site, where His is separated from CXXC by Ser residue is more effective in binding Zn2+ and Ni2+ ions than the C-terminal site, in which His is adjacent to the CXXC motif. Studies on various modifications of the peptide sequence within the Ac-ELECKDCSHVFKPNALDYGVCEKCHS-NH2 loop show the role of the residues in the linker between the CXXC motifs and the effect of the length of the linker on the stability of the complexes it forms with Zn2+, Cd2+ and Ni2+ ions. The proline residue in the linker between the two CXXC binding sites plays a distinct role in the metal ion binding ability of the loop, lowering the efficacy of the metal ion coordination. The deletion of the aliphatic residues from the linker between the CXXC motifs remarkably improves the binding efficacy of the loop. [ABSTRACT FROM AUTHOR]

The effect of Cu 2+ on α-synuclein (AS) aggregation is important because clinical studies of patients with Parkinson's disease have shown elevated levels of Cu 2+ in the cerebrospinal fluid. So far, the molecular architectures of Cu 2+ -AS fibril complexes at atomic resolution are unknown. The current work identifies for the first time that His50 cannot bind Cu 2+ ions in mature fibrils. Moreover, it shows hopping of Cu 2+ ions between residues in AS fibrils and changes in the Cu 2+ coordination mode in Cu 2+ ions that bind in the termini of AS. The current study combines extensive experimental techniques, density functional theory calculations, and computational modeling tools to provide a complete description of the Cu 2+ binding site in AS fibrils. Our findings illustrate for the first time the specific interactions between Cu 2+ ions and AS fibrils, suggesting a new mechanistic perspective on the effect of Cu 2+ ions on AS aggregation.

The zinc binding loop domain of the HypA protein of Helicobacter pylori consists of two CXXC motifs with flanking His residues. These motifs bind metal ions, and thus they are crucial for the functioning of the whole protein. The N-terminal site, where His is separated from CXXC by Ser residue is more effective in binding Zn(2+) and Ni(2+) ions than the C-terminal site, in which His is adjacent to the CXXC motif. Studies on various modifications of the peptide sequence within the Ac-ELECKDCSHVFKPNALDYGVCEKCHS-NH2 loop show the role of the residues in the linker between the CXXC motifs and the effect of the length of the linker on the stability of the complexes it forms with Zn(2+), Cd(2+) and Ni(2+) ions. The proline residue in the linker between the two CXXC binding sites plays a distinct role in the metal ion binding ability of the loop, lowering the efficacy of the metal ion coordination. The deletion of the aliphatic residues from the linker between the CXXC motifs remarkably improves the binding efficacy of the loop.