Copper effective binding with 32-62 and 94-125 peptide fragments of histone H2B.
In an attempt to investigate the role of histone H2B in Cu(II) induced toxicity and carcinogenesis, we synthesized the terminally blocked peptides H2B(32-62) (SRKESYSVYVYKVLKQVH(48)PDTGISSKAMGIM) and Η2Β(94-125) (IQTAVRLLLPGELAKH(110)AVSEGTKAVTKYTSS), mimicking the N-terminal histone-fold domain and C-terminal tail of histone H2B, respectively and studied their interaction with Cu(II) ions by means of potentiometric titrations and spectroscopic techniques (UV-visible, CD and EPR). Both peptides, H2B(32-62) and H2B(94-125), interacted efficiently with Cu(II) ions, forming several species from pH 4 to 11, with His(48) and His(110) serving as anchors for metal binding. In H2B(32-62), the effective Cu(II) binding is emphasized by the formation of a soluble Cu(II)-H2B(32-62) complex, unlike the unbound peptide that precipitated over pH 7.9. At physiological pH, both peptides form tetragonal 3N species with a {N(Im), 2N(-)} coordination mode. At this pH, H2B(32-62) presented the formation of coordination isomers, differentiated by the presence in one of them, of an axial coordination of the carboxylate group of Asp(50). Copper binding with both H2B(32-62) and H2B(94-125) may induce a conformational change in the peptides' original structure. At physiological conditions, this effect may interfere with nucleosome's structure and dynamics, including the ubiquitination of Lys(120) which is linked to gene silencing.
Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece.
Kimon
K
Zavitsanos
Ana Mónica
AM
Nunes
Gerasimos
G
Malandrinos
Nick
N
Hadjiliadis
D002942:Circular Dichroism; D003300:Copper / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D006657:Histones / Q000737:chemistry*; D008958:Models, Molecular; D010446:Peptide Fragments / Q000737:chemistry*; D011199:Potentiometry
D006657:Histones; D010446:Peptide Fragments; D003300:Copper