The electrophile Ca(2+) is an essential multifunctional co-factor in the phospholipase A(2) mediated hydrolysis of phospholipids. Crystal structures of an acidic phospholipase A(2) from the venom of Bothrops jararacussu have been determined both in the Ca(2+) free and bound states at 0.97 and 1.60 A resolutions, respectively. In the Ca(2+) bound state, the Ca(2+) ion is penta-coordinated by a distorted pyramidal cage of oxygen and nitrogen atoms that is significantly different to that observed in structures of other Group I/II phospholipases A(2). In the absence of Ca(2+), a water molecule occupies the position of the Ca(2+) ion and the side chain of Asp49 and the calcium-binding loop adopts a different conformation. 相似文献
A comparative study was made of the metabolizing activity of microsomal fractions of the liver of the rat, mouse, Chinese hamster, dog, mini-pig, rhesus monkey and baboon, with and without pretreatment of the animals with Aroclor (500 mg/kg i.p.). The activity of the fractions was determined by means of the Salmonella/mammalian-microsome mutagenicity test. The protein content of the S9 fractions was standardized (36.14 mg/ml) to eliminate species-specific and inter-individual differences. Strain TA100 of Salmonella typhimurium was used as test organism. The substances tested, namely benzo[a]pyrene, cyclophosphamide, diethylnitrosamine, β-naphthylamine and o-aminoazotoluene, are all known mutagens or carcinogens belonging to various chemical classes.
The tests made with S9 fractions from animals that had not been pretreated with Aroclor revealed distinct species-specific differences in the metabolizing activity of the fractions and also differences from one substance to another. The fractions from mice and Chinese hamster had only a weakly positive effect with some of the substances, those from the rat and the mini-pig only with 2 and 3 of the 5, resp. The dog-liver fraction gave positive results with all substances except benzo[a]pyrene. The fractions from the baboon and the rhesus monkey had positive to strongly positive effects with all the substances.
In the experiments in which the animals had been pretreated with Aroclor, the S9 fractions from all species produced positive effects with all substances, and the mutagenic effects provoked by various substances, when fractions from untreated animals were used, remained of the same degree or became more distinct. Species-specific differences were no longer discernible.
Demethylase activity in all the S9 fractions used was determined with ethylmorphine. Without prior activation, the fractions from the mouse, Chinese hamster, rat and dog gave highly divergent values. In the fractions from the mini-pig, the baboon and, in particular, the rhesus monkey, the activity was relatively more pronounced. Enzyme induction with Aroclor led to a distinct increase in demethylase activity in the livers of almost all species. Only a very rough quantitative relation was evident between the demethylase activity of the individual S9 fractions and their influence on the substances tested for mutagenicity. 相似文献
Insects ensure the survival of their offspring by depositing their eggs in suitable environments. Even generalist egg-laying insects often show preferences for specific host plants. The cocoa pod borer (CPB), Conopomorpha cramerella (Snellen) (Lepidoptera: Gracillariidae), successfully infests and reproduces on relatively few host plants, but has a major economic impact only on cocoa, Theobroma cacao L. (Malvaceae). Choice tests were performed in the laboratory to compare the frequency of insect visits, the duration of the visits, and the number of eggs laid on the fruits for each combination of host plants tested – that is, cocoa clones or fruits of rambutan (Nephelium lappaceum L.), Fijian longan (Pometia pinnata JR Forst & G Forst, both Sapindaceae), and langsat (Lansium domesticum Corrêa, Malvaceae). Our laboratory study showed that, when given the choice, CPB significantly favored cocoa pods over other host fruits (rambutan, langsat, or Fijian longan). Females also deposited more eggs on unripe fruits than on ripe fruits of similar size. The preference to lay eggs on specific cocoa clones in the bioassays did not reflect the level of the clone resistance to CPB damage reported from the field. Consequently, oviposition preference of female CPB does not seem to be the main factor explaining field resistance of some cocoa clones to CPB infestation. 相似文献
Laser-capture microdissection (LCM) enables the selection of a specific and pure cell population from a heterogenous tissue such as tumors. Activity-based protein profiling/profile (ABPP) is a chemical technology using enzyme-specific active site-directed probes to read out the functional state of many enzymes directly in any proteome. The aim of this work was to assess the compatibility of LCM with downstream ABPP for serine hydrolase (SH) in human lung adenocarcinoma. Fresh frozen lung adenocarcinoma tissue was stained with hematoxylin, toluidine blue, or methyl green (MG). Proteome from stained tissue was labeled further with SH-directed probes, and ABPPs were determined on a one-dimensional gel-based approach. This allowed us to assess the impact of staining procedures on their ABPPs. The effect of the LCM process on ABPPs was assessed furthermore using MG-stained lung adenocarcinoma tissue. The staining procedures led to strong changes in ABPPs. However, MG staining seemed the most compatible with downstream ABPP. MG-stained, laser-captured, microdissected tissue showed additional change in profiles as a result of the denaturing property of extraction buffer but not to the microdissection process itself. LCM staining procedures but not microdissection per se interfered with downstream ABPP and led to a strong change in ABPPs of SHs in human lung adenocarcinoma. 相似文献