Cm. Nunn et al., A MODEL FOR THE [C-G-CENTER-DOT-C](N) TRIPLE-HELIX DERIVED FROM OBSERVATION OF THE C+-G-CENTER-DOT-C BASE TRIPLET IN A CRYSTAL-STRUCTURE(), FEBS letters, 416(1), 1997, pp. 86-89
A molecular modelling study on the [C+-G . C](11) triple helix is repo
rted, We have observed the C+-G . C base triplet in the crystal struct
ure of an oligonucleotide-drug complex, between the minor-groove drug
netropsin and the decanucleotide d(CGCAATTGCG)(2). The complex was cry
stallised at pH 7.0, but the crystal structure, at a resolution of 2.4
Angstrom, shows that a terminal cytosine has become protonated and pa
rticipates in a parallel C+-G . C base triplet, The structure of this
triplet and its associated sugar-phosphate backbones have been energy-
refined and then used to generate a triple helix, This has characteris
tics of the B-type family of DNA structures for two strands, with the
third, the C+ strand, having backbone conformations closer to the A fa
mily. (C) 1997 Federation of European Biochemical Societies.