Photoreactivity of 5-iodouracil-containing DNA-Sso7d complex in solution: the protein-induced DNA kink causes intrastrand hydrogen abstraction from the 5-methyl of thymine at the 5' side.

Photoirradiation of 5-iodouracil-containing DNA, d(GTAAT(I)UAC)(2) with Sso7d protein, possessing significant kink in DNA in the crystal structure induces an unprecedented intrastrand H abstraction at the methyl group of T(5), together with selective photooxidations at Met29 of Sso7d. The reactivity of the deoxyuridin-5-yl radical can be explained by the crystal structure of the d(GTAATTAC)(2)-Sso7d complex, suggesting that the interaction of DNA-Sso7d in solution is substantially similar to its crystal structure.