Evidence for crystal environment dominating base sequence effects on DNA conformation: crystal structures of the orthorhombic and hexagonal polymorphs of the A-DNA decamer d(GCGGGCCCGC) and comparison with their isomorphous crystal structures.
We have determined the structure of the A-DNA decamer d(GCGGGCCCGC) in two crystal forms, orthorhombic and hexagonal, at 1.7- and 1.8-A resolution, respectively. In the orthorhombic form, the fifth guanine residue has nearly trans-trans conformations for the alpha-gamma backbone torsions, as in the isomorphous orthorhombic structure d(CCCGGCCGGG) [Ramakrishnan, B., & Sundaralingam, M. (1993) J. Mol. Biol. 231, 431-444]. However, in the hexagonal form, the eighth cytosine residue adopts the trans-trans conformations for the backbone alpha-gamma torsions, as in the isomorphous hexagonal structure d(ACCGGCCGGT) [Frederick, C. A., Quigley, G. J., Teng, M.-K., Coll, M., van der Marel, G. A., van Boom, J. H., Rich, A., & Wang, A. H.-J. (1989) Eur. J. Biochem. 181, 295-307]. Even though the average helix and base-pair parameters are nearly the same in the two polymorphous crystal forms having the same sequence, many of the base-dependent local helix parameters are quite different. However, in the isomorphous crystal forms, in spite of the differing base sequences, the local helix and base-pair parameters of the duplexes are nearly the same. This indicates that, in crystals, the local conformation of a DNA structure is affected severely by the crystal packing environment rather than by the base sequence.
Ramakrishnan
B
B
Department of Chemistry, Ohio State University, Columbus 43210-1002.
Sundaralingam
M
M
D001483:Base Sequence; D003460:Crystallization; D004247:DNA / Q000737:chemistry*; D006860:Hydrogen Bonding; D007202:Indicators and Reagents; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000138:chemical synthesis / Q000737:chemistry*; D013329:Structure-Activity Relationship; D014961:X-Ray Diffraction / Q000379:methods
D007202:Indicators and Reagents; D009838:Oligodeoxyribonucleotides; D004247:DNA