1j8l
From Proteopedia
Molecular and Crystal Structure of D(CGCAAATTMO4CGCG): the Watson-Crick Type N4-Methoxycytidine/Adenosine Base Pair in B-DNA
Overview
To investigate the mutation mechanism of purine transitions in DNA damaged with methoxyamine, a DNA dodecamer with the sequence d(CGCAAATTmo(4)CGCG), where mo(4)C is 2'-deoxy-N(4)-methoxycytidine, has been synthesized and the crystal structure determined by X-ray analysis. The duplex structure is similar to that of the original undamaged B-form dodecamer, indicating that the methoxylation does not affect the overall DNA conformation. Electron density maps clearly show that the two mo(4)C residues form Watson-Crick-type base pairs with the adenine residues of the opposite strand and that the methoxy groups of mo(4)C adopt the anti conformation to N(3) around the C(4)-N(4) bond. For the pair formation through hydrogen bonds the mo(4)C residues are in the imino tautomeric state. Together with previous work, the present work establishes that the methoxylated cytosine residue can present two alternate faces for Watson-Crick base-pairing, thanks to the amino<-->imino tautomerism allowed by methoxylation. Based on this property, two gene transition routes are proposed.
About this Structure
Full crystallographic information is available from OCA.
Reference
Crystallographic studies on damaged DNAs IV. N( 4)-methoxycytosine shows a second face for Watson-Crick base-pairing, leading to purine transition mutagenesis., Hossain MT, Sunami T, Tsunoda M, Hikima T, Chatake T, Ueno Y, Matsuda A, Takenaka A, Nucleic Acids Res. 2001 Oct 1;29(19):3949-54. PMID:11574676 Page seeded by OCA on Fri May 2 20:55:16 2008
