CRYSTAL STRUCTURE OF THE B-DNA DECAMER D(CGCAATTGCG)2; SEQUENCE-DEPENDENT CROSSED HELIX PACKING. Alexis A. Wood, Christine M. Nunn, Stephen Neidle, The CRC Biomolecular Structure Unit, The Institute of Cancer Research, Cotswold Road, Sutton, Surrey, SM2 SNG, UK
The B-DNA decamer d(CGCAATTGCG)2 has been found to crystallise in the monoclinic space group C2 and packs with a crossed arrangement of helices and a unique crossing contact distinct from all other decamer structures. This is believed to be a direct result of the sequence-dependent conformational features of the duplex. Two unique sites are observed at the cross-over junction where strand exchange may occur if this structure were to be used as a model for the Holliday juction. It is also a rare example of a B-DNA sequence crystallising in two different space groups by variation of crystallisation conditions alone. The structure has been solved to a resolution of 2.3Å and an R-factor of 17.7%.