Coordination properties of Cu(II) and Ni(II) ions towards the C-terminal peptide fragment -TYTEHA- of histone H4.
In order to reveal more information about the toxicity caused by metals and furthermore their influence to the physiological metabolism of the cell, the hexapeptide model Ac-ThrTyrThrGluHisAla-am representing the C-terminal 71-76 fragment of histone H4 which lies into the nucleosome core, was synthesized. A combined pH-metric and spectroscopic UV-VIS, EPR, CD and NMR study of Ni(II) and Cu(II) binding to the blocked hexapeptide, revealed the formation of octahedral complexes involving imidazole nitrogen of histidine, at pH 5 and pH 7 for Cu(II) and Ni(II) ions respectively. In basic solutions a major square-planar 4 N Ni(II)-complex, adopting a {N(Im), 3N(-)} coordination mode, was formed. In the case of Cu(II) ions, a 3 N complex, involving the imidazole nitrogen of histidine and two deprotonated amide nitrogens of the backbone of the peptide, at pH 7 and a series of 4 N complexes starting at pH 6.5, were suggested. In addition Ni(II)-mediated hydrolysis of the peptide bond-Tyr-Thr was evident following our experimental data.
Karavelas
T
T
University of Ioannina, Department of Chemistry, Ioannina, 45110, Greece.
Malandrinos
G
G
Hadjiliadis
N
N
Mlynarz
Piotr
P
Kozlowski
Henryk
H
Barsan
M
M
Barsam
M
M
Butler
I
I
D003300:Copper / Q000737:chemistry*; D006657:Histones / Q000737:chemistry*; D006868:Hydrolysis; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D009942:Organometallic Compounds / Q000737:chemistry*; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000737:chemistry*; D010455:Peptides; D011485:Protein Binding; D013053:Spectrophotometry
D006657:Histones; D009942:Organometallic Compounds; D010446:Peptide Fragments; D010455:Peptides; D003300:Copper; D009532:Nickel