To determine the location of the non-substrate-ligand-binding region in mammalian glutathione Stransferases, fluorescence-resonance energy transfer was used to calculate distances between tryptophan residues and protein-bound 8-anilinonaphthalene 1-sulphonate (an anionic ligand) in the human class-a glutathione S-transferase, and in a human Trp284Phe mutant class-n glutathione S-transferase. Distance values of 2.21 nm and 1.82 nm were calculated for the class-a and class-n enzymes, respectively. Since glutathione S-transferases bind one non-substrate ligandprotein dimer, the ligand-binding region, according to the calculated distances, is found to be located in the dimer interface near the twofold axis. This region is the same as that in which the parasitic helminth Schistosoma japonicum glutathione S-transferase binds praziquantel, a non-substrate drug used to treat schistosomiasis Mol. Biol. 246,. Since the overall folding topology is conserved and certain features at the dimer interface are similar throughout the superfamily, it is reasonable to expect that all cytosolic glutathione S-transferases bind non-substrate ligands in the amphipathic groove at the dimer interface.Keywords: glutathione S-transferase; energy transfer; non-substrate ligand; 8-anilinonaphthalene 1 -sulfonate.Cytosolic glutathione S-transferases (GST) a superfamily of heterodimeric and homodimeric proteins, catalyse the nucleophilic addition of the thiol of reduced glutathione (y-glutamylcysteinylglycine) to electrophilic centres in a wide variety of hydrophobic electrophiles, including alkyl and aryl halides, epoxides, quinones and activated alkenes (Armstrong, 1991). Although they can be grouped into five species-independent gene classes ( a, p, z, r~ and O), GST share a common protein fold (Dirr et al., 1994a). Three-dimensional structures of isoenzymes from the a (Sinning et al., 1993;Cameron et al., 1995), p (Ji et al., 1992Raghunathan et al., 1994), n (Reinemer et al., 1992; Dim et al., 1994b; Garcia-Saez et al., 1994), r~ (Ji et al., 1995) and B (Wilce et al., 1995; Reinemer et al., 1996) classes have been determined, and this abundance of structural information has provided much insight into the protein-architectural relationships between the different gene classes. Each glutathione Stransferase subunit is folded into two distinct structural domains. Domain 1 has an papappa folding topology, in which its conserved core provides the principal framework for the active site. Domain 2 has an all-a-type core structure. There are two structurally independent active siteddimer, each of which consists of a glutathione-binding site (G-site) and an electrophilic-hydrophobic-substrate-binding site (H-site).

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Laboratory studies were carried out to compare the toxicity of the chloronicotinyl insecticide, imidacloprid on parasitoids. The studies took place at the Tamil Nadu Agricultural University, Coimbatore from 2006-2007. Imidacloprid was tested against three beneficial insects viz., an egg parasitoid, egg larval parasitoid and a larval parasitoid representing two families of Hymenoptera:Trichogrammatidae (Trichogramma chilonis Ishii) and Braconidae (Chelonus blackburni Cameron; Bracon hebetor Say) that attack insect pests of cotton. The toxicity of imidacloprid was evaluated by treating the parasitized eggs using an atomizer in the case of T. chilonis and glass scintillation vial residue bioassay method for the adults of C. blackburni and B. hebetor. The toxicity of imidacloprid to parasitoids was compared with another neonicotinoid, named thiamethoxam, and a standard check, methyl demeton. Imidacloprid 17.8 SL did not cause any adverse effects on the adult emergence and parasitization of T. chilonis. At the recommended dose of imidacloprid [25 g active substance (a.s.)/ha], 90.67 and 85.32 per cent adult emergence and parasitization was recorded, respectively. The recommended dose of imidacloprid caused 56 per cent mortality and was found to have moderate impact on the adults of C. blackburni. On the other hand, it was found to be toxic to the parasitoid B. hebetor, causing 70 per cent mortality at 48 hours after treatment (HAT). The data presented here will provide pest managers with specific information on the compatibility of selected insecticides with natural enemies attacking pests of cotton, Gossypium hirsutum L.

Treatment of diploid human fibroblasts with an alkylating mutagen has been shown to induce stable, anchorage-independent cell populations at frequencies (11 X 10-4) consistent with an activating mutation. After treatment of human foreskin fibroblasts with the mutagen benzo[alpyrene (±)anti-7,8-dihydrodiol 9,10-epoxide and selection in soft agar, 17 anchorage-independent clones were isolated and expanded, and their cellular DNA was used to cotransfect NIH 3T3 cells along with pSV2neo. DNA from 11 of the 17 clones induced multiple NIH 3T3 cell tumors in recipient nude mice. Southern blot analyses showed the presence of human Alu repetitive sequences in all of the NIH 3T3 tumor cell DNAs. Intact, human HRAS sequences were observed in 2 of the 11 tumor groups, whereas no hybridization was detected when human KRAS or NRAS probes were used. Slow-migrating ras p21 proteins, consistent with codon 12 mutations, were observed in the same two NIH 3T3 tumor cell groups that contained the human HRAS bands. Genomic DNA from one of these two human anchorage-independent cell populations (clone 21A) was used to enzymatically amplify a portion of exon 1 of the HRAS gene. Direct sequence analysis of the amplified DNA indicated equal presence of a wild-type (GGC) and mutant (GTC) allele of the HRAS gene. The results demonstrate that exposure of normal human cells to a common environmental mutagen yields HRAS GC -+ TA codon 12 transversions that have been commonly observed in human tumors. This oncogene as well as an as yet to be identified oncogene are also shown to stably confer anchorageindependence to human cells.

Toxicity and the effect of sub-lethal concentrations of endosulfan On a fresh water fish Barbus stigma had been studied. Eadosulfan proved to be lethal to B. stigma at a concentration of 0'01 ppm and above. The Lew was 0'0043 ppm and the sub-lethal concentration was 0·t!03 ppm and below. At sub-lethal concentrations the fish exhibited erratic swimming activity and at lethal concentrations it lost the sense of balance. The rate of feeding was reduced by 5'94% to 9'02% and assimilation by 6'44 to 9'60% in different sub-lethal concentrations. Growth (weight) retarded from U~6mg/daY in the control fish to 7'3,6'0 and 5'1 mg! day in the endosulfan treated fishes. Respiratory rate of the pesticide treated fish also dropped by 10 to 16'6%. Due to the over all effect of the toxicity, the fish. B. stigma comparatively showed a poor nutritive value by displaying a drop of nearly 35% in the organic constituents.