A new crystal form for the dodecamer C-G-C-G-A-A-T-T-C-G-C-G: Symmetry effects on sequence-dependent DNA structure

The dodecanucleotide d(CGCGAATTCGCG) has been crystallised in the space gro up P3(2)12, representing a new crystal form for this sequence. The structur e has been solved by molecular replacement and refined at 1.8 Angstrom reso lution. The present structure contrasts with previous ones for this sequenc e since it is situated on a crystallographic 2-fold axis, and the crystal s ymmetry reflects the palindromic nature of this sequence. Some features acc ord with previous observations, notably that the minor groove is hydrated w ith a continuous spine of solvent. There is no evidence of alkali metal ion s within this spine. The minor groove retains its narrow width, although it is now symmetric and extends over the A/T tract. Various base and base-pai r morphological parameters have been examined. Their values do not show sig nificant correlations with earlier reports, suggesting that crystal packing effects on them are more dominant than has been hitherto realised. (C) 200 0 Academic Press.