1D27

HIGH-RESOLUTION STRUCTURE OF A MUTAGENIC LESION IN DNA

Summary for 1D27

• Entry DOI: 10.2210/pdb1d27/pdb
• Descriptor: DNA (5'-D(*CP*GP*CP*(6OG)P*AP*AP*TP*TP*TP*GP*CP*G)-3') (2 entities in total)
• Functional Keywords: b-dna, double helix, modified, mismatched, dna
• Total number of polymer chains: 2
• Total formula weight: 7384.86

Authors

Leonard, G.A.,Thomson, J.,Watson, W.P.,Brown, T. (deposition date: 1991-04-22, release date: 1992-04-07, Last modification date: 2024-02-07)

Primary citation

Leonard, G.A.,Thomson, J.,Watson, W.P.,Brown, T.
High-resolution structure of a mutagenic lesion in DNA.
Proc.Natl.Acad.Sci.USA, 87:9573-9576, 1990

PubMed Abstract: The self-complementary dodecanucleotide d[CGC(m6G)AATTTGCG]2 (where m6G is O6-methylguanine), which contains two m6G.T base pairs, has been analyzed by x-ray diffraction methods and the structure has been refined to a residual error of R = 0.185 at 2.0-A resolution. The m6G.T mispair closely resembles a Watson-Crick base pair and there are very few structural differences between the m6G.T duplex and the native analogue. The similarity between the m6G.T base pair and a normal G.C base pair explains the failure of mismatch repair enzymes to recognize and remove this mutagenic lesion. A series of ultraviolet melting studies over a wide pH range on a related dodecamer indicate that the m6G.C mispair can exist in two conformations; one is a wobble pair and the other is a protonated Watson-Crick pair. The former, which predominates at physiological pH, will be removed by normal proofreading and repair enzymes, whereas the latter is likely to escape detection. Hence, the occasional occurrence of the protonated m6G.C base pair may explain why the presence of m6G in genomic DNA does not always give rise to a mutation.

PubMed: 2263612
DOI: 10.1073/pnas.87.24.9573

Experimental method

X-RAY DIFFRACTION (2 Å)