title: An NMR study on nickel binding sites in Cap43 protein fragments.
abstract: NMR spectroscopy was used to study the interaction of Ni(II) ions with C-terminal sequence of Cap43 protein where, from Thr341 to Gly360 residue, a T1R2S3R4S5H6T7S8E9G10 ten-amino acid fragment is consecutively repeated three times. The behaviour of ends-blocked Ac-RSRSHTSEG-Am (pept1), Ac-TRSRSHTSEG-Am (pept2), and the three repeats Ac-TRSRSHTSEG-TRSRSHTSEG-TRSRSHTSEG-Am (pept3) peptides towards Ni(II) ions was examined at different pH values and, for pept3, at different ligand-to-metal molar ratios. 1H-1H TOCSY, 1H-13C HSQC, 1H-1H NOESY and 1H-1H ROESY multidimensional NMR techniques were performed to understand the details of metal binding sites and the conformational behaviour of the peptides. The results confirmed that each mono-histidinic sequence of pept3 is able to independently coordinate one, two or three Ni(II) ions for 1:1, 1:2 and 1:3 ligand-to-metal molar ratios, respectively. At higher pH values, the coordination of Ni(II) involves imidazole Ndelta of His6 and three preceding deprotonated peptide nitrogens from the backbone, giving a {Ndelta, 3N-} chromophore in a square planar geometry. In addition, at lower pH values, the involvement of gamma-O of carboxyl group from Glu9 residue with the formation of a macrochelate giving a {Ndelta, gamma-O-, 4O(H2O)} chromophore in an octahedral geometry, was evidenced. NMR results allowed us to build a model for the structure of the major complex. Structural changes in the conformation of the peptide with organized Arg4 and Thr7 side chain orientation promoted by nickel coordination, were detected.
authors: Department of Chemistry, University of Sassari, Italy. zoroddu@uniss.it
authors: Maria Antonietta
authors: MA
authors: Zoroddu
authors: Massimiliano
authors: M
authors: Peana
authors: Serenella
authors: S
authors: Medici
authors: Roberto
authors: R
authors: Anedda
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009532:Nickel / Q000378:metabolism*; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D000099259:N-myc Downstream-Regulated Gene 1 Protein
chemical_list: D018797:Cell Cycle Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009532:Nickel; D000099259:N-myc Downstream-Regulated Gene 1 Protein