A novel endonuclease from kinetoplastid hemoflagellated protozoan parasite Leishmania.

A nuclease activity has been purified from the nuclei-kinetoplast fraction of Leishmania. This enzyme, termed endonuclease M (Endo M), is shown by electrophoresis in a denaturing polyacrylamide gel to be associated with a single polypeptide of molecular mass 52 kDa. Physical analysis of the enzyme indicates that it has a sedimentation coefficient S20,w of 4.5S, a Stoke's radius of 32.5 A, and a native molecular mass of 53 kDa. The final Mono Q purified Endo M possesses both DNase and RNase activities. It acts as an endonuclease by introducing random single-stranded nicks into the supercoiled DNA molecules, that often leads to its linearization due to nicking at the opposite strands, and subsequent degradation of the DNA with further incubation. Single-stranded DNA is twice preferred to double-stranded DNA as substrate. Single-stranded RNA is also degraded rapidly and is competitive as a substrate with single-stranded DNA. RNA:DNA hybrids, however, are largely resistant to the Endo M digestion.

Chromatographic separation of DNA dependent RNA polymerases and molecular properties of RNA polymerase II from a Leishmania Spp.

Multiple forms of DNA-dependent RNA polymerases have been isolated and characterized from Leishmania strain UR6 promastigotes. RNA polymerases from this organism fail to resolve into multiple forms by conventional chromatography on DEAE-Sephadex A25, but could be separated by a modification of the method using CM-Sephadex C25. The CM-Sephadex bound enzyme is resistant to alpha-amanitin even up to a concentration of 250 micrograms/ml. The activity which flows through CM-Sephadex further resolves into two forms upon chromatography on DEAE-Sephadex A25. These forms are sensitive to alpha-amanitin to different extent. Enzyme activity in peak I is 50% inhibited by 3 micrograms/ml and in peak II by 50 micrograms/ml of the drug respectively. The enzyme in peak I has been further purified by heparin agarose and fast performance liquid chromatography (FPLC) on MonoQ. The enzyme has Stoke's radius of 70 A, a sedimentation coefficient of 17.6S and an f/fo of 1.35. Analysis of ammonium sulfate and metal ion optima of the enzyme in peak I, relative activities with Mn+2 versus Mg+2 and template specificities gave results similar to those reported for other type II RNA polymerases in eukaryotes. The MonoQ purified enzyme resolves into 16 polypeptides on denaturing polyacrylamide gel and densitometric analysis suggests that 9 major bands are present in the stoichiometry expected of RNA polymerase subunits having molecular weights: 154000; 104000; 77000; 64000; 52000; 48000; 46000; 45000 and 39000 respectively.

Dual inhibition of DNA topoisomerases of Leishmania donovani by novel indolyl quinolines.

omoindolyl)]ty of biologically active compounds contain indole and quinoline nuclei. A one step synthesis of some novel indolyl quinoline analogs e.g. 2-(2"-Dichloro-acetamidobenzyl)-3-(3'-indolyl)-quinoline [1], 2-(2"-Dichloroacetamido-5"-bromobenzyl)-3'-[3'-(5'-bromoindolyl ] -6-bromo quinoline [2], and 2-(2"-acetamido benzyl)-3-(3'-indolyl)-quinoline [3] has been developed under Friedel-Crafts acylation conditions. The compounds inhibit the relaxation and decatenation reactions catalysed by type I and type II DNA topoisomerases of Leishmania donovani. Among the three synthetic indolyl quinolines, the Br-derivative [2] is most active. The results reported here concerning the inhibition of type I and type II DNA topoisomerases indicate that the compounds act as "dual inhibitors" of the enzymes and can be exploited for rational drug design in human leishmaniasis.