Sequence specific molecular recognition and binding by a GC recognizing Hoechst 33258 analogue to the decadeoxyribonucleotide d-[CATGGCCATG]2: structural and dynamic aspects deduced from high field 1H-NMR studies.
The non-exchangeable and imino proton NMR resonances have been assigned of the 1:1 complex of an analogue 2 of Hoechst 33258 1 bound to the decadeoxyribonuycleotide d-[CATGGCCATG]2 by a combination of NOE difference, COSY and NOESYPH techniques. In contrast to Hoechst 33258 which recognizes 5'-AATT sequences exclusively, analogue 2 possesses structural features designed to permit the recognition of GC sites. The NOESY and 1D-NOE experiments place the drug in the minor groove and it is located on the 5'-CCAT sequence. The orientation of the drug in the groove is such as to place the N-methylpiperazine terminus at a GC site. Cross-correlation peaks in the NOESY experiment show that the DNA duplex retains its right-handed B form, similar to that in the free decamer. Specific NOEs locate the benzoxazole moiety on the 5'-CCAT and are consistent with the pyridine nitrogen forming a new hydrogen bond to G(4)-2NH2 at 5'-CCAT. The drug appears to undergo rotation around the C9-C10 bond, at a rate comparable with NMR time scale, even after binding. Variable temperature 1H-NMR studies established that the DNA is thermally stabilized as a result of the drug binding. The drug binding is a dynamic process involving exchange between the equivalent 5'-CCAT sites at approximately 60s-1 with delta G degree of 65 kJ mol-1 at 308K. The experimental evidence is in accord with a slide-swing mechanism for this process.
Department of Chemistry, University of Alberta, Edmonton, Canada.
S
S
Kumar
B
B
Yadagiri
J
J
Zimmermann
R T
RT
Pon
J W
JW
Lown
D001483:Base Sequence; D001665:Binding Sites; D006690:Bisbenzimidazole / Q000737:chemistry* / Q000378:metabolism; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D006859:Hydrogen; D006860:Hydrogen Bonding; D007098:Imino Acids; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D013816:Thermodynamics; D014961:X-Ray Diffraction
D007098:Imino Acids; D006859:Hydrogen; D004247:DNA; D006690:Bisbenzimidazole