Molecular and crystal structure of d(CGCGmo4CG): N4-methoxycytosine.guanine base-pairs in Z-DNA.
The base analogue N4-methoxycytosine (mo4C) is ambivalent in its hydrogen-bonding potential, since it forms stable base-pairs with both adenine and guanine in oligomer duplexes. To investigate the base-pair geometry, the structure of d(CGCGmo4CG) has been determined by single-crystal X-ray diffraction techniques. The d(CGCGmo4CG)2 crystallized in a left-handed double helical structure (Z-type). Refinement using 2559 reflections between 10 and 1.7 A converged with a final R = 0.181 (Rw = 0.130) including 68 solvent molecules. The orthorhombic crystals are in the space group P2(1)2(1)2(1), with cell dimensions a = 18.17 A, b = 30.36 A, c = 43.93 A. The mo4C.G base-pair is of the wobble type, with mo4C in the imino form, and the methoxy group in the syn configuration.
Van Meervelt
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University of Chemical Laboratory, Cambridge, U.K.
Moore
M H
MH
Lin
P K
PK
Brown
D M
DM
Kennard
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O
D001482:Base Composition; D001483:Base Sequence; D003596:Cytosine / Q000031:analogs & derivatives* / Q000737:chemistry; D004247:DNA / Q000737:chemistry*; D003854:Deoxyribonucleotides / Q000737:chemistry*; D006147:Guanine / Q000737:chemistry*; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D014961:X-Ray Diffraction
D003854:Deoxyribonucleotides; C036689:N(4)-methoxycytosine; D006147:Guanine; D003596:Cytosine; D004247:DNA