Inhibition of Human Immunodeficiency Virus Type 1 Integrase by a Hydrophobic Cation: The Phenanthroline-Cuprous Complex

Abstract

The human immunodeficiency virus type 1 integrase (HIV-1 integrase) is required for integration of a double-stranded DNA copy of the viral RNA genome into a host chromosome and for HIV replication. We have examined the effects of 2:1 1,10-phenanthroline-cuprous complexes on purified HIV-1 integrase. Although the uncomplexed phenanthrolines are not active below 100 microM, four of the cuprous complexes (neocuproine, 4-phenyl neocuproine, 2,3,4,7,8,9-hexamethyl phenanthroline, and 2,3,4,7,8-pentamethyl phenanthroline) have a 50% inhibitory concentration (IC50) for integration ranging between 1 and 10 microM. Disintegration is also inhibited by these phenanthroline-cuprous complexes at slightly higher concentrations (between 10 and 40 microM). Dialysis experiments showed that the inhibition is reversible and kinetic analyses revealed that the mode of inhibition by these cuprous complexes appears to be noncompetitive with respect to the substrate DNA. Consistent with these findings, binding assays demonstrate that, although these complexes can inhibit binding to DNA at high concentrations, they do not inhibit binding of integrase to the DNA substrate at their IC50 values. Because these complexes do not bind to B-DNA below 50 microM, inhibition via binding to a specific region on the enzyme was examined. Using deletion mutants of integrase, it was determined that neither the amino-terminal (zinc finger) nor the carboxy-terminal (DNA-binding) integrase domain is required for inhibition by the phenanthroline-cuprous complexes. Therefore, inhibition via binding to the enzyme catalytic core or to the interface between the enzyme and a noncanonical DNA structure generated during the enzymatic reaction is the probable mechanism. These results suggest the utility of neocuproine-cuprous complexes in developing inhibitors of HIV-1 integrase as well as probes for drug-binding sites and enzymatic reaction mechanism.

HIV integrase: a target for drug discovery

“…To date, most inhibitors of HIV IN belong to the class of low-molecular-mass compounds identified from natural sources and chemical libraries. Examples for these mainly aromatic compounds are: caffeic acid phenethyl ester and its derivatives [124][125][126], flavones [126,127], tyrphostins [128], bis-catechols [129], lignans [130], aurintricarboxylic acid [131], curcumin [132,133], phenanthroline-cuprous complex [134], dicaffeoylquinic acid [135] and cosalane analogues [136] (see Table 1). Structure-activityrelationship analysis demonstrated that most of these compounds contain aromatic polyhydroxylated aromatic rings separated by an aliphatic spacer [125].…”

Interaction of metal chelators with different molecular forms of acetylcholinesterase and its significance in Alzheimer's disease treatment

“…: enzymes involved in oxidative phosphorylation, human immunodeficiency virus type 1 integrase) functions. Such modulatory effects are brought about by its specific direct binding to the enzyme catalytic core site and not through its chelation property.…”

Reaction with DNA and pharmacologic activity of 1,10-phenanthroline and electron-rich 1,10-phenanthrocyanine complexes of d-elements

“…Even though free 1,10-phenanthrolines are inactive at concentrations below 100 µM, Cu(I) bis-1,10-phenanthroline complexes with neocuproine, 4-phenylneocuproine, as well as 2,3,4,-7,8,9-hexamethyl-1,10-phenanthroline and 2,3,4,7,8-pentamethyl-1,10-phenanthroline inhibit HIV-I viruses (IC 50 for integrative ranging vary between 1 and 10 µM). Disintegrative inhibition by these complexes occurs at slightly higher concentrations, between 10 and 40 µM) [151,152].…”

“…Over the past years the complexes of transition metals, especially Cu(I), with 1,10-phenanthroline and its derivatives (neocuproine, 4-phenylneocuproine, bathocuproine dusolfonic acid) have attracted enhanced interest as agents inhibiting HIV-1 and HIV-2 viruces [151][152][153][154]. Heterocyclic agents inhibiting HIV-1 and HIV-2 viruses at 50% inhibitory concentrations (IC 50 ) of 0.006 and 0.01 µg ml -1 , respectively, were synthesized on the basis of 2,9-bis(bromomethyl)-1,10-phenanthroline [155].…”