γ-Hydroxy-1,N²-propano-2′-deoxyguanosine DNA Adduct Conjugates the N-Terminal Amine of the KWKK Peptide via a Carbinolamine Linkage

Abstract

The γ-hydroxy-1,N2-propano-2′-deoxyguanosine adduct (γ-OH-PdG) was introduced into 5′-d(GCTAGCXAGTCC)-3′·5′-d(GGACTCGCTAGC)-3′ (X = γ-OH-PdG). In the presence of excess peptide KWKK, 13C isotope-edited NMR revealed the formation of two spectroscopically distinct DNA–KWKK conjugates. These involved the reaction of the KWKK N-terminal amino group with the N2-dG propylaldehyde tautomer of the γ-OH-PdG lesion. The guanine N1 base imino resonance at the site of conjugation was observed in isotope-edited 15N NMR experiments, suggesting that the conjugated guanine was inserted into the duplex and that the guanine imino proton was protected from exchange with water. The conjugates could be reduced in the presence of NaCNBH3, suggesting that they existed, in part, as imine (Schiff base) linkages. However, 13C isotope-edited NMR failed to detect the imine linkages, suggesting that these KWKK conjugates existed predominantly as diastereomeric carbinolamines, in equilibrium with trace amounts of the imines. The structures of the diastereomeric DNA–KWKK conjugates were predicted from potential energy minimization of model structures derived from the refined structure of the fully reduced cross-link [Biochemistry2010246155]. Molecular dynamics calculations carried out in explicit solvent suggested that the conjugate bearing the S-carbinolamine linkage was the major species due to its potential for intramolecular hydrogen bonding. These carbinolamine DNA–KWKK conjugates thermally stabilized duplex DNA. However, the DNA–KWKK conjugates were chemically reversible and dissociated when the DNA was denatured. In this 5′-CpX-3′ sequence, the DNA–KWKK conjugates slowly converted to interstrand N2-dG:N2-dG DNA cross-links and ring-opened γ-OH-PdG derivatives over a period of weeks.

Characterization of the Deoxyguanosine–Lysine Cross-Link of Methylglyoxal

“…DPCs have also been characterized from chemotherapeutic agents such as nitrogen mustards and cisplatin . DPCs can form reversibly with abasic sites − or enal adducts − of dGuo via Schiff base formation with a lysine side chain or the N-terminal amino group; such DPCs have been reductively trapped.…”

Mitochondrial DNA damage and its consequences for mitochondrial gene expression

“…Acrolein creates the hydroxy-l, N 2 -propano-dG adducts, α-and γ-OH-PdG, with γ-OH-PdG being the major product [13]. The γ-OH-PdG adduct may further react with nearby functional groups to form DNA interstrand crosslinks and protein-DNA crosslinks [70–72]. Considering the PUFA enrichment of the IMM, α,β-unsaturated aldehydes are likely a major threat to mtDNA stability and gene expression during tissue oxidative stress.…”

New Views on the Reaction of Primary Amine and Aldehyde from DFT Study

“…8 They further discussed the chemistry of interstrand cross-links induced by unsaturated aldehydes derived from lipid peroxidation and environmental sources. 9 The study of the native DNA−KWKK linkage 10 found that the stabilization of the DNA to thermal denaturation may be improved by carbinolamine-linked DNA− KWKK by intramolecular hydrogen bonding, and theoretical calculation suggests that the carbinolamine-linked DNA− KWKK conjugates exist with the peptide located in the minor groove. For another example, Munõz's group performed some related studies on Schiff base formation in the vitamin B6 system with the aid of theoretical methods.…”