An extremely stable Ni(II) complex derived from the hydrolytic cleavage of the C-terminal tail of histone H2A

Nickel Toxicity and Carcinogenesis

“…However, the binding is followed by hydrolysis of the E-S peptide bond with formation of the SHHKAKGK peptide. The latter binds nickel very strongly through the SHH-motif, yielding a square planar complex [203] that is redox-active at physiological pH. Its reaction with H 2 O 2 results in oxidation of the Ser and His residues of -TESHHK-and collateral oxidative damage to DNA, if added to the reaction mixture [176].…”

Nickel Ion Complexes of Amino Acids and Peptides

“…Above pH 7 SHHK and SAHK (hydrolysis products) coordinate to Ni(II) equatorially through the imidazole of His-3, the N-terminal amino group, and the two amide nitrogens located between Ser-1 and His-3, {NH 2 , 2N Ϫ , N im }, forming 4N albumin-like square planar complexes [141]. Spectroscopic evidence and theoretical predictions suggest that the positioning of the free imidazole ring, in the Ni-SHHK complex, above the coordination plane, induces the extra stability of the complex [142].…”

Solution structure of a designed cyclic peptide ligand for nickel and copper ions

“…Interestingly, all of the protons of the lysine residue except for one of the H ε protons shift dramatically downfield upon Ni(II) binding. Downfield shifts for amino-terminal H α protons upon metal complexation have been observed before, 14,15 but the other protons of the N-terminal residue are not typically altered. While the effect of heavy atoms on chemical shift remains difficult to predict, 17 deshielding of these protons is consistent with being conformationally restricted and being held in the vicinity of the Ni(II) ion.…”