title: Cu(II) and Ni(II) interactions with the terminally blocked hexapeptide Ac-Leu-Ala-His-Tyr-Asn-Lys-amide model of histone H2B (80-85).
abstract: The N- and C-terminal blocked hexapeptide Ac-Leu-Ala-His-Tyr-Asn-Lys-amide (LAHYNK) representing the 80-85 fragment of histone H2B was synthesized and its interactions with Cu(II) and Ni(II) ions were studied by potentiometric, UV-Vis, CD, EPR, and NMR spectroscopic techniques in solution. Our data reveal that the imidazole N(3) nitrogen atom is the primary ligating group for both metal ions. Sequential amide groups deprotonation and subsequent coordination to metal ions indicated an {N(imidazole), 3N(amide)} coordination mode above pH approximately 9, in all cases. In the case of Cu(II)-peptide system, the almost exclusive formation of the predominant species CuL in neutral media accounting for almost 98% of the total metal ion concentration at pH 7.3 strongly indicates that at physiological pH values the sequence -LAHYNK- of histone H2B provides very efficient binding sites for metal ions. The imidazole pyrrole N(1) ionization (but not coordination) was also detected in species CuH(-4)L present in solution above pH approximately 11.
authors.affiliation: Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece.
authors.forename: Katerina
authors.initials: K
authors.lastname: Panagiotou
authors.forename: Maria
authors.initials: M
authors.lastname: Panagopoulou
authors.forename: Tilemachos
authors.initials: T
authors.lastname: Karavelas
authors.forename: Vassiliki
authors.initials: V
authors.lastname: Dokorou
authors.forename: Andrew
authors.initials: A
authors.lastname: Hagarman
authors.forename: Jonathan
authors.initials: J
authors.lastname: Soffer
authors.forename: Reinhard
authors.initials: R
authors.lastname: Schweitzer-Stenner
authors.forename: Gerasimos
authors.initials: G
authors.lastname: Malandrinos
authors.forename: Nick
authors.initials: N
authors.lastname: Hadjiliadis