Crystal structure of d(AGG(Br)CATGCCT): Implications for cobalt hexammine binding to DNA

The crystal structure of the DNA decamer d(AGG(Br)CATGCCT) has been determined to a resolution of 2.0 Angstrom and R factor of 19.6%. Crystals of d(AGG(Br)CATGCCT) were grown in the presence of cobalt hexammine but no cobalt hexammine ions are bound to the DNA structure. This contrasts with the recently determined crystal structure of d(AGGCATGCCT) which has a similar DNA conformation and cobalt hexammine ions bound directly to the DNA. Comparison with the structure of d(AGGCATGCCT) and appreciation of the crystal packing of this sequence leads to an understanding of how cobalt hexammine binding to DNA occurs and its role in determining DNA conformation.