title: Discrimination of A/T sequences in the minor groove of DNA within a cyclic polyamide motif.
abstract: Eight-ring cyclic polyamides containing pyrrole (Py), imidazole (Im), and hydroxypyrrole (Hp) aromatic amino acids recognize predetermined six base pair sites in the minor groove of DNA. Two four-ring polyamide subunits linked by (R)-2,4-diaminobutyric acid [(R)H2Ngamma] residue form hairpin polyamide structures with enhanced DNA binding properties. In hairpin polyamides, substitution of Hp/Py for Py/Py pairs enhances selectivity for T. A base pairs but compromises binding affinity for specific sequences. In an effort to enhance the binding properties of polyamides containing Hp/Py pairings, four eight ring cyclic polyamides were synthesized and analyzed on a DNA restriction fragment containing three 6-bp sites 5'-tAGNNCTt-3', where NN = AA, TA, or AT. Quantitative footprint titration experiments demonstrate that contiguous placement of Hp/Py pairs in cyclo-(gamma-ImPyPyPy-(R)H2Ngamma-ImHpHpPy-) (1) provides a 20-fold increase in affinity for the 5'-tAGAACTt-3' site (Ka = 7.5 x 10(7)M(-1)) relative to ImPyPyPy-(R)H2Ngamma-ImHpHpPy-C3-OH (2). A cyclic polyamide of sequence composition cyclo-(gamma-ImHpPyPy-(R)H2Ngamma-ImHpPyPy-) (3) binds a 5'-tAGTACTt-3' site with an equilibrium association constant KA= 3.2 x 10(9)M(-1), representing a fivefold increase relative to the hairpin analogue ImHpPyPy-(R)H2Ngamma-ImHpPyPy-C3-OH (4). Arrangement of Hp/Py pairs in a 3'-stagger regulates specificity of cyclo-(gamma-ImPyHpPy-(R)H2Ngamma-ImPyHpPy-) (5) for the 5'-tAGATCTt-3' site (Ka = 7.5 x 10(7)M(-1)) threefold increase in affinity relative to the hairpin analogue ImPyHpPy-(R)H2Ngamma-ImPyHpPy-C3-OH (6), respectively. This study identifies cyclic polyamides as a viable motif for restoring recognition properties of polyamides containing Hp/Py pairs.
authors.affiliation: Arnold and Mabel Beckman Laboratories of Chemical Synthesis, California Institute of Technology, Pasadena 91125, USA.
authors.forename: C
authors.initials: C
authors.lastname: Melander
authors.forename: D M
authors.initials: DM
authors.lastname: Herman
authors.forename: P B
authors.initials: PB
authors.lastname: Dervan
mesh_terms: D000225:Adenine / Q000737:chemistry; D001483:Base Sequence; D004247:DNA / Q000737:chemistry*; D004270:DNA, Circular / Q000138:chemical synthesis / Q000737:chemistry; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009757:Nylons / Q000138:chemical synthesis / Q000737:chemistry*; D011758:Pyrroles / Q000737:chemistry; D017422:Sequence Analysis, DNA / Q000379:methods; D013379:Substrate Specificity; D013941:Thymine / Q000737:chemistry
chemical_list: D004270:DNA, Circular; D009757:Nylons; D011758:Pyrroles; D004247:DNA; D000225:Adenine; D013941:Thymine