1qkg
From Proteopedia
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DNA DECAMER DUPLEX CONTAINING T-T DEWAR PHOTOPRODUCT
Overview
In contrast to the highly mutagenic pyrimidine(6-4)pyrimidone, photoproduct, its Dewar valence isomer (Dewar product) has low mutagenic, potential and produces a broad range of mutations [LeClerc, J. E., Borden, A. & Lawrence, C. W. (1991) Proc. Natl. Acad. Sci. USA 88, 9685-9689]. To, determine the origin of the mutagenic property of the Dewar product, we, used experimental NMR restraints and molecular dynamics to determine the, solution structure of a Dewar-lesion DNA decamer duplex. This DNA decamer, duplex (DW/GA duplex) contains a mismatched base pair between the 3' T, residue of the Dewar lesion (T6) and an opposed G residue (G15). The 3' T, (T6) of the Dewar lesion formed stable hydrogen bonds with the opposing, G15 residue. However, the helical bending and unwinding angles of the, DW/GA duplex were much larger than those of a second duplex that contains, the Dewar lesion and opposing A15 and A16 residues (DW/AA duplex). The, DW/GA duplex showed poorer stacking interactions at the two bases of the, Dewar product and at the adjacent A7 small middle dotT14 base pair than, did the DW/AA duplex. These structural features imply that no thermal, stability or conformational benefit is obtained by incorporating a G, instead of an A opposite the 3' T of the Dewar lesion. These properties, may thus facilitate the preferential incorporation of an A in accordance, with the A rule during translesion replication and lead to the low, frequency of 3' T-->C mutations observed at this site.
About this Structure
1QKG is a Protein complex structure of sequences from [1]. Full crystallographic information is available from OCA.
Reference
The Dewar photoproduct of thymidylyl(3'-->5')- thymidine (Dewar product) exhibits mutagenic behavior in accordance with the "A rule"., Lee JH, Bae SH, Choi BS, Proc Natl Acad Sci U S A. 2000 Apr 25;97(9):4591-6. PMID:10758155
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