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DNA-Bound Peptide Radicals Generated through DNA-Mediated Electron Transport

Wagenknecht, Hans-Achim and Stemp, Eric D. A. and Barton, Jacqueline K. (2000) DNA-Bound Peptide Radicals Generated through DNA-Mediated Electron Transport. Biochemistry, 39 (18). pp. 5483-5491. ISSN 0006-2960. doi:10.1021/bi992897m.

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Flash-quench experiments were carried out to explore peptide/DNA electron-transfer reactions. DNA-bound [Ru(phen)_2(dppz)]^(3+) (phen = 1,10-phenanthroline; dppz = dipyridophenazine) and [Ru(phen)(bpy‘)(dppz)]^(3+) [bpy‘ = 4-(4‘-methyl-2,2‘-bipyridyl)valerate], generated in situ by flash-quench methodology, are powerful ground-state oxidants, capable of oxidizing guanine or tyrosine intercalated in DNA. In flash-quench experiments with mixed-sequence oligonucleotides in the presence of Lys-Tyr-Lys, transient absorption spectroscopy yielded a spectrum with a sharp maximum at 405 nm assigned to the tyrosine radical. Experiments with poly(dG·dC) suggested the intermediacy of the guanine radical, since the rise of the 405 nm signal occurred with the same kinetics as the disappearance of the guanine radical, as monitored at 510 nm. In oligonucleotide duplexes containing [Ru(phen)(bpy‘)(dppz)]^(2+) tethered at one end, damage to distant guanines was observed by gel electrophoresis, consistent with the mobility of the electron hole through the DNA duplex; the presence of the peptide did not inhibit but instead altered the distribution of guanine damage. Covalent adducts of the DNA and Lys-Tyr-Lys were detected as final irreversible products of this peptide-to-DNA electron-transfer chemistry by mass spectrometric and enzymatic digestive analysis. From these different assays and comparison of reactions of Lys-Trp-Lys and Lys-Tyr-Lys, the reactivity of the DNA-bound tyrosine radical was found to differ considerably from that of the tryptophan radical. These results establish that Lys-Tyr-Lys and Lys-Trp-Lys can participate in long-range electron-transfer reactions through the DNA from a distinct binding site. On that basis, proposals for functional roles for these peptide radicals may be considered.

Item Type:Article
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URLURL TypeDescription
Stemp, Eric D. A.0000-0003-2098-4214
Barton, Jacqueline K.0000-0001-9883-1600
Additional Information:© 2000 American Chemical Society. Received December 17, 1999; Revised Manuscript Received February 16, 2000. Publication Date (Web): March 31, 2000. We are grateful to NIH for financial support (GM49216 to J.K.B.). We thank the Swiss National Science Foundation and the Novartis Foundation for a postdoctoral fellowship to H.A.W., Mount St. Mary’s College for a professional development grant, and NSF (MCB981-7338) for funding of E.D.A.S.
Funding AgencyGrant Number
Swiss National Science Foundation (SNSF)UNSPECIFIED
Novartis FoundationUNSPECIFIED
Mount St. Mary’s CollegeUNSPECIFIED
Issue or Number:18
Record Number:CaltechAUTHORS:20160209-145158250
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Official Citation:DNA-Bound Peptide Radicals Generated through DNA-Mediated Electron Transport Hans-Achim Wagenknecht, Eric D. A. Stemp, and Jacqueline K. Barton Biochemistry 2000 39 (18), 5483-5491 DOI: 10.1021/bi992897m
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64344
Deposited By: George Porter
Deposited On:09 Feb 2016 23:17
Last Modified:10 Nov 2021 23:29

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