Computer modeling of gibberellin-DNA binding

Computer modeling and molecular mechanics performed on the intercalation complexes of selected gibberellins or biosynthetic precursors with DNA dinucleotides revealed that under appropriate conditions the ligands insert (intercalate) between the base-paired double-stranded dinucleotide, 5'-dTdA-3'. Stabilization of the double-stranded dinucleotide after docking of a gibberellin between base pairs is inferred by the sum negative energy of hydrogen bonding and van der Waals contacts and the entropic changes which accompany the formation of each ligand-dinucleotide complex. In addition, the interactions of the gibberellins and dinucleotides, with the gibberellic acid-dinucleotide complex serving as the prototype, show optimum geometry and stereochemical hydrogen bonding recognition which are dependent upon the complementary chirality and stereochemistry of the individual components. Whether or not the gibberellins directly influence the uncoiling of DNA or gene expression at the transcriptional level via an intercalation mechanism is a matter of conjecture, albeit one that warrants intensive investigation.