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The crystal structure of the oligonucleotide d(CGCAAATTO8GGCG), containing the chemically modified base 8-hydroxydeoxyguanine (O8G), has been determined at 2.5-A resolution and refined to a crystallographic R-factor of 16.8%. The B-type DNA helix contains standard Watson-Crick base pairs except at the mismatch sites, where O8G adopts a syn conformation and forms hydrogen bonds to adenine in the anti conformation. The thermodynamic stability of the duplex was found by UV melting techniques to be intermediate between the native oligonucleotide d(CGCAAATTTGCG) and an oligonucleotide containing A.G mispairs d(CGCAAATTGGCG). Comparison of the structure of the O8G(syn).A(anti) base pair with those of Watson-Crick base pairs has given a reason why O8G.A base pairs are not well repaired by DNA proofreading enzymes.

Type

Journal article

Journal

Biochemistry

Publication Date

30/08/1994

Volume

33

Pages

10266 - 10270

Keywords

Adenine, Amino Acid Sequence, Base Composition, Crystallization, DNA, DNA Repair, Deoxyguanosine, Models, Molecular, Molecular Sequence Data, Molecular Structure, Nucleic Acid Conformation, Nucleic Acid Heteroduplexes, Oligodeoxyribonucleotides, Thermodynamics