Adam P. Silverman, W. Bu, Seth M. Cohen
Dec 20, 2002
Citations
1
Influential Citations
58
Citations
Journal
The Journal of Biological Chemistry
Abstract
cis-trans-cis-Ammine(cyclohexylamine)diacetatodichloroplatinum(IV) is an oral analog of the platinum anti-cancer drug cisplatin that is currently in phase III clinical trials. Its active form, {Pt(ammine)(cyclohexylamine)}2+, binds to DNA similarly to cisplatin, forming intra- and interstrand cross-links between adjacent purine bases. Since {Pt(ammine)(cyclohexylamine)}2+ contains two different ligands, it can form two isomeric 1,2-d(GpG) intrastrand cross-links. Here we report the 2.4-Å resolution x-ray crystal structure of the major adduct between {Pt(ammine)(cyclohexylamine)}2+ and a DNA dodecamer, using the same sequence as previously reported for crystal structures of cisplatin-DNA (Takahara, P. M., Rosenzweig, A. C., Frederick, C. A., and Lippard, S. J. (1995)Nature 377, 649–652) and oxaliplatin-DNA (Spingler, B., Whittington, D. A., and Lippard, S. J. (2001) Inorg. Chem. 40, 5596–5602). Both duplexes in the asymmetric unit contain 1,2-intrastrand cross-links in which the cyclohexylamine ligand is directed toward the 3′-end of the platinated strand. The chair conformation of the cyclohexyl group is clearly resolved. Platination distorts the duplex, resulting in a global bend angle of about 38o and a dihedral angle between platinated guanine bases of ∼31o. Both end-to-end and end-to-groove packing interactions occur in the crystal lattice, the latter positioned in the minor groove across from the site of the platinum cross-link. A high degree of homology observed between this structure and the previously reported platinum-DNA structures suggests that these platinum complexes distort the DNA duplex in a very similar manner. These results suggest that differences in activity between these drugs are unlikely to result from gross conformational distortions in DNA structure following platinum intrastrand cross-link formation.