Nuclear magnetic resonance structural studies and molecular modeling of duplex DNA containing normal and 4'-oxidized abasic sites.Chen, J., Dupradeau, F.Y., Case, D.A., Turner, C.J., Stubbe, J.
(2007) Biochemistry 46: 3096-3107
- PubMed: 17323932
- DOI: https://doi.org/10.1021/bi6024269
- Primary Citation of Related Structures:
2HOU, 2HPX, 2HSK, 2HSL, 2HSR, 2HSS
- PubMed Abstract:
A 4'-oxidized abasic site (X) has been synthesized in a defined duplex DNA sequence, 5'-d(CCAAAGXACCGGG)-3'/3'-d(GGTTTCATGGCCC)-5' (1). Its structure has been determined by two-dimensional NMR methods, molecular modeling, and molecular dynamics simulations. 1 is globally B-form with the base (A) opposite X intrahelical and well-stacked. Only the alpha anomer of X is observed, and the abasic site deoxyribose is largely intrahelical. These results are compared with a normal abasic site (Y) in the same sequence context (2). Y is composed of a 60:40 mixture of alpha and beta anomers (2alpha and 2beta). In both 2alpha and 2beta, the base (A) opposite Y is intrahelical and well-stacked and the abasic site deoxyribose is predominantly extrahelical, consistent with the reported structures of the normal abasic site in a similar sequence context [Hoehn, S. T., Turner, C. J., and Stubbe, J. (2001) Nucleic Acids Res. 29, 3413-3423]. Molecular dynamics simulations reveal that the normal abasic site appears to be conformationally more flexible than the 4'-oxidized abasic site. The importance of the structure and flexibility of the abasic site in the recognition by the DNA repair enzyme Ape1 is discussed.
Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.