Co(II) and Mn(II) binding to a multihistidinic peptide

A multi-histidinic (T1R2S3R4S5H6T7S8E9G10)3 peptide fragment from Cap43 protein, has been investigated for Mn(II) and Co(II) binding, in order to relate its coordination behaviour to the biological implications in the protein structure. UV-Visible spectroscopy together with 1H NMR measurements have been used to investigate the role of multi-histidinic sites in coordinating metals. Both ions showed common binding donor atoms: manganese and cobalt binding centre was mainly associated with histidines. The specific perturbation of NMR resonances indicated that coordination involves imidazole of His6, with the possibility of involvement of carboxyl γ-O of Glu9 and hydroxyl γ-O of Thr7 in the minimal model peptide (9-aa). Manganese and cobalt coordination involves, primarily, all the three imidazolic nitrogens of His6, His16, His26, and, probably, carboxyl γ-O of Glu9, Glu19, and Glu29, in the three repeats, the 30-aminoacid fragment (30-aa).