Structures of two minor-groove-binding quinolinium quaternary salts complexed with d(CGCGAATTCGCG)2 at 1.6 and 1.8 Å resolution

The structures of the complexes formed between two anticancer minor-groove-binding quinolinium quaternary salts and the dodecamer d(CGCGAATTCGCG) 2 have been refined to resolutions of 1.6 and 1.8 angstrom. The complexes crystallized in space group P2(1)2(1)2(1) and the structures are isomorphous with previously solved dodecamer structures. The ligands both bind in the central AT region of the minor groove and although the crystallization conditions and structures of the ligands are very similar, they bind in opposing orientations. The structures are compared with two previously published structures of quinolinium quaternary salts, refined at 2.5 angstrom resolution, complexed with d(CGCGAATTCGCG)(2) and an e(6)G-modified DNA.