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Mechanism of nickel assault on the zinc finger of DNA repair protein XPA.
- Source :
-
Chemical research in toxicology [Chem Res Toxicol] 2003 Feb; Vol. 16 (2), pp. 242-8. - Publication Year :
- 2003
-
Abstract
- Xeroderma pigmentosum group A complementing protein (XPA) is a member of the protein complex of the nucleotide excision repair (NER) pathway of DNA repair, participating in the assembly of the incision complex. The 4S zinc finger domain of XPA is involved the interactions with other NER proteins. As demonstrated previously, the activity of XPA is compromised by several metal ions implicated in DNA repair inhibition, including Ni(II), Cd(II), and Co(II) (Asmuss, M., Mullenders, L. H. F., Elker, A., and Hartwig, A. (2000) Carcinogenesis 21, 2097-2104). To study the possible molecular mechanisms of XPA inhibition, we investigated Zn(II) and Ni(II) interactions with the synthetic 37 peptide (XPAzf), representing the XPA zinc finger sequence AcDYVICEECGKEFMDSYLMNHFDLPTCDNCRDADDKHKam. The binding constants were determined using fluorescence and UV-vis spectroscopies, structural insights were provided by CD, and oxidative damage to XPAzf was studied with HPLC. The binding constants for Zn(II) and Ni(II) are (8.5 +/- 1.5) x 10(8) (log value 8.93(7)) and (1.05 +/- 0.07) x 10(6) M(-)(1) (6.02(3)), respectively, in 10 mM phosphate buffer, pH 7.4, and (6 +/- 4) x 10(9) (9.8(2)) and (2.9 +/- 0.5) x 10(6) M(-)(1) (6.46(8)) in 50 mM phosphate buffer, pH 7.4, yielding binding constant ratios Zn(II)/Ni(II) of 800 +/- 100 and 2300 +/- 500, respectively. The Ni(II) ion forms a square planar complex with the sulfurs of XPAzf, opposed to the tetrahedral structure of the native Zn(II) complex. Consequently, the overall zinc finger structure is lost in the Ni(II)-substituted peptide. Zn(II)-saturated XPAzf is remarkably resistant to air oxidation and is only slowly oxidized by 0.01 mM, 0.1 mM, and 1 mM H(2)O(2) in a concentration-dependent fashion. However, the presence of just 10-fold molar excess of Ni(II) is sufficient to accelerate this process for all three H(2)O(2) concentrations tested. Overall, our results indicate that XPAzf can undergo Ni(II) assault in specific conditions.
- Subjects :
- Amino Acid Sequence
DNA Repair drug effects
DNA Repair physiology
DNA-Binding Proteins chemical synthesis
Kinetics
Models, Molecular
Molecular Sequence Data
Nickel chemistry
Nickel toxicity
Oxidation-Reduction drug effects
Protein Binding
Protein Structure, Secondary
Spectrum Analysis methods
Thermodynamics
Xeroderma Pigmentosum Group A Protein
Zinc chemistry
Zinc metabolism
Zinc Fingers physiology
DNA-Binding Proteins antagonists & inhibitors
DNA-Binding Proteins metabolism
Nickel metabolism
Zinc Fingers drug effects
Subjects
Details
- Language :
- English
- ISSN :
- 0893-228X
- Volume :
- 16
- Issue :
- 2
- Database :
- MEDLINE
- Journal :
- Chemical research in toxicology
- Publication Type :
- Academic Journal
- Accession number :
- 12588196
- Full Text :
- https://doi.org/10.1021/tx025639q