Products of the reaction between a diazoate derivative of 2 '-deoxycytidine and L-lysine and its implication for DNA-nucleoprotein cross linking by NO or HNO2
T. Suzuki et al., Products of the reaction between a diazoate derivative of 2 '-deoxycytidine and L-lysine and its implication for DNA-nucleoprotein cross linking by NO or HNO2, CHEM RES T, 13(12), 2000, pp. 1223-1227
Recently, we have reported that a stable diazoate intermediate (dCyd-diazoa
te) is produced upon the reaction of dCyd with nitrous acid and nitric oxid
e [Suzuki, T., Nakamura, T., Yamada, M., Ide, H., Kanaori, K., Tajima, K.,
Morii, T., and Makino, K. (1999) Biochemistry 38, 7151-7158]. In this work,
the reaction of dCyd-diazoate with L-Lys was investigated. When 0.4 mM dCy
d-diazoate was incubated with 10 mM L-Lys in sodium phosphate buffer (pH 7.
4) at 37 degreesC, two unknown products were formed in addition to dUrd. By
spectrometric measurements, the products were identified as dCyd-Lys adduc
ts with C4(dCyd)-N-alpha(Lys) and C4(dCyd)-N-epsilon(Lys) linkages (abbrevi
ated as dCyd-alpha Lys and dCyd-epsilon Lys, respectively). The yields at t
he reaction time of 72 h were 28.0% dCyd-alpha Lys, 13.4% dCyd-epsilon Lys,
and 11.1% dUrd with 33.9% unreacted dCyd-diazoate. When 0.4 mM dCyd-diazoa
te was incubated with 22 mg/mL poly(L-lys) at pH 7.4 and 37 degreesC for 24
h, 82% of the free dCyd-diazoate disappeared, indicating adduct formation
with the polymer. At pH 7.4 and 37 degreesC, dCyd-alpha Lys and dCyd-ELys w
ere fairly stable and gave rise to no product after incubation for 7 days.
At pH 4.0 and 70 degreesC, both adducts disappeared with the same first-ord
er rate constant of 1.7 x 10(-6) s(-1) (t(1/2) = 110 h), which was similar
to1/3 of that of dCyd. These results suggest that if dCyd-diazoate is forme
d in DNA in vivo, it may react with free L-Lys and the side chain of L-Lys
in nucleoproteins, resulting in stable adducts and DNA-protein cross-links,
respectively.