RESUMEN
On the basis of a structural analysis of 240 protein-DNA complexes contained in the Protein Data Bank (PDB), we have classified the DNA-binding proteins involved into eight different structural/functional groups, which are further classified into 54 structural families. Here we present this classification and review the functions, structures and binding interactions of these protein-DNA complexes.
Asunto(s)
Proteínas de Unión al ADN/química , ADN/química , Animales , Cristalografía por Rayos X , ADN/metabolismo , Proteínas de Unión al ADN/clasificación , Proteínas de Unión al ADN/fisiología , Humanos , Sustancias Macromoleculares , Relación Estructura-ActividadRESUMEN
Improved rationally designed lead drug structures against African trypanosomiasis, Chagas disease, and leishmaniasis were obtained against trypanothione reductase from Trypanosoma cruzi. Substituted-benzyl [3-(2-chloro-4a, 10a-dihydrophenothiazin-10-yl)propyl]dimethylammonium salts, synthesized by Menschutkin quaternization of the tertiary alkylamine omega-nitrogen atom of chlorpromazine, were linear, competitive inhibitors of recombinant trypanothione reductase from T. cruzi, with either trypanothione disulfide or N-benzyloxycarbonyl-L-cysteinylglycyl 3-dimethylaminopropylamide disulfide as substrate. The permanent positive charge on the distal nitrogen atom of the tricyclic side chain contribution to binding was estimated as >/=5.6 kcal.mol(-1) by comparison with the analogue with the cationic nitrogen atom of the quaternary replaced by an ether oxygen atom. A further major contribution to improving K(i) values and inhibition strength was the hydrophobic natures and structures of the N-benzyl substituents. The strongest inhibitor, the [3-(2-chloro-4a,10a-dihydrophenothiazin-10-yl)propyl](3, 4-dichlorobenzyl)dimethylammonium derivative (K(i) 0.12 microM), was approximately 2 orders of magnitude more inhibitory than the parent chlorpromazine. Several of these quaternary phenothiazines completely inhibited T. brucei parasite growth in vitro at <1 microM. Antiparasite activity was not solely determined by inhibition strength against trypanothione reductase, there being a strong contribution from hydrophobicity (for example, benzhydryl-quaternized chlorpromazime had ED(50) < 1 microM). Although active against Leishmania donovani, none of the analogues showed major improvement in this activity relative to chlorpromazine or other nonquaternized phenothiazines. The p-tert-butylbenzyl-quaternized analogue very strongly inhibited (ED(50) < 1 microM) growth of the amastigote stage of T. cruzi.
Asunto(s)
Antiparasitarios/síntesis química , Inhibidores Enzimáticos/síntesis química , NADH NADPH Oxidorreductasas/antagonistas & inhibidores , Fenotiazinas/síntesis química , Compuestos de Amonio Cuaternario/síntesis química , Animales , Antiparasitarios/química , Antiparasitarios/farmacología , Sitios de Unión , Clorpromazina/análogos & derivados , Clorpromazina/síntesis química , Clorpromazina/química , Clorpromazina/farmacología , Diseño de Fármacos , Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/farmacología , Técnicas In Vitro , Concentración 50 Inhibidora , Leishmania donovani/efectos de los fármacos , Ligandos , Macrófagos Peritoneales/parasitología , Ratones , Modelos Moleculares , Fenotiazinas/química , Fenotiazinas/farmacología , Compuestos de Amonio Cuaternario/química , Compuestos de Amonio Cuaternario/farmacología , Relación Estructura-Actividad , Trypanosoma brucei brucei/efectos de los fármacos , Trypanosoma cruzi/químicaRESUMEN
The parasite enzyme trypanothione reductase has been used as a target for rational drug design against trypanosomiasis and leishmaniasis in a number of laboratories. In this article the biochemical basis for its selection as a target is reviewed. The relevant structural aspects of the target are then compared with the homologous structure found in the mammalian hosts to indicate the molecular basis by which selective toxicity is likely to be achieved. An overview of known classes of inhibitors is provided, preparatory to a detailed coverage of approaches that have been taken to obtaining strong, selective inhibitors and the steps taken in the process of the initial discovery of tricyclic structures by interactive molecular graphics ligand design are outlined. Recent quantitative docking approaches which have been applied to this system are also described. Finally, the biological data of the activity against the various parasitic forms in vitro and in vivo are summarised.