The tetrahedral cuprous complexes of 1,10-phenanthroline and certain of its derivatives inhibit RNA and DNA polymerases at concentrations less than 1 micron. The octahedral complexes of 4,7-diphenyl-1, 10-phenanthroline with ferrous, nickel, or ruthenium ions are inhibitory at comparable concentrations. The mechanisms and specificity of the potent inhibition by these geometrically distinct complexes will be explored using kinetics, spectroscopy, and equilibrium dialysis. The specificity of the inhibition for eukaryotic and procaryotic RNA and DNA polymerases of differing metabolic function will be studied as a function of primer/template and coordination complex structure. Since these coordination complexes are among the most potent synthetic inhibitors known for polymerases, they should be useful tools in studying nucleic acid replication and obvious candidates for trial as anticancer drugs. The function of the tightly bound zinc ion in RNA and DNA polymerases will be explored by kinetic studies on the removal of the metal ion by chelating agents from the enzymes or the bound zinc's exchange with free 65Zn ion in solution. The effects of substrates or inhibitors on either process will suggest possible roles for this essential zinc ion. The partial reactions and ligand binding properties of the metal-free apoenzymes will also suggest potential functions of the metal ion. General anesthetics facilitate a ligand induced structural transition in the membrane-bound acetylcholine receptor protein which can be monitored in vitro using the binding of a snake toxin. Since this conformational change may be responsible for desensitization at neuromuscular junctions, this system provides an attractive model for the mode of action of general anesthetics. Detailed kinetic and fluorescence studies on this ligand induced conformational change will be carried out in the presence of general anesthetics and calcium and zinc ion to determine the mechanism of this structual transition and the effects of specific ions and protein-lipid interactions on this membrane associated property.
NIH ExPorter
NIH ExPorter