Proteomic Analysis of Glutathione Transferases from Lucilia Cuprina

<p>The glutathione transferases are a family of multifunctional enzymes involved in detoxification of xenobiotic and endogenous electrophilic compounds. Interest in insect GSTs has primarily focused on their role in insecticide resistance. The sheep blowfly, Lucilia cuprina is a major economic problem for the sheep meat and wool industries in Australasia and hence this thesis has attempted the study of the Lucilia cuprina GST family, using proteomics, with a view to eventually determining their role in insecticide resistance. Combinations of different affinity matrices (glutathione-Sepharose matrix (GSH) followed by dinitrophenyl-glutathione-Sepharose matrix (DNP-GSH)) and two-dimensional electrophoresis has successfully isolated members from major four insect GST classes: Sigma, Delta, Epsilon and Omega. Drosophila melanogaster has been used as a model insect throughout as a basis for comparison. To characterise Lucilia GSTs, the whole metazoan fragmentation database was used for sequence alignment with Lucilia peptides. This approach is broad and speculative but predicts a possible classification of the GSTs based on % similarity and % identity. This method of characterisation yielded match scores that provided a basis for classification, which must at present be regarded as tentative and in need of confirmation. In D. melanogaster and L. cuprina, GSH affinity-purified extracts showed the presence of only Sigma and Delta GSTs. In D. melanogaster, the DNP-GSH affinity-purified GSTs showed mostly the presence of Epsilon and Omega GSTs whereas in L. cuprina no Omega GSTs were detected. In both species, the migration pattern of Delta GST on 2D PAGE gel indicated possible post-translational modification. The results from analysis of LC-MS/MS data by the software PEAKS suggested deamidation at asparagine and glutamine residues in a limited number of the matched peptides of Delta GST. GST activity was present in all developmental stages of L. cuprina. The number of isoenzymes and their extent of expression vary as the insect develops. Delta GSTs were present in all developmental stages. The Sigma GST started expressing from the larval stage and was abundantly present in adult stage. The DNP-GSH affinity matrix purified GSTs which have been tentatively classified as Mu-like GSTs were present in egg, larvae and pupae but totally absent in adult stage. The GST families were characterised by proteomics in the main body sections of L. cuprina. Higher GST activity towards 1-chloro-2, 4-dinitrobenzene (CDNB) was found in the thorax (65.2 %) followed by the abdomen (19.6%) and the head (15.2%). The cytosolic GSTs of a resistant strain (PY81) of L. cuprina had significantly higher (2.26- and 2.6- fold) activity than the susceptible strains (NSW and CSIRO) towards CDNB and 2, 3-dichloro, 4-nitrobenzene (DCNB) respectively. The proteomic analysis of DNP-GSH purified extract from susceptible and resistant strains showed quantitatively higher expression of GSTs on 2D PAGE gel of the PY81 strain. The in vitro interaction of purified GSTs and model insecticides studied by high performance liquid chromatography revealed that Delta and DNP-GSH affinity-purified GSTs catalyse the conjugation of the insecticides to reduced glutathione but Sigma GST had almost no activity.</p>

Proteomic Analysis of Glutathione Transferases from Lucilia Cuprina

<p>The glutathione transferases are a family of multifunctional enzymes involved in detoxification of xenobiotic and endogenous electrophilic compounds. Interest in insect GSTs has primarily focused on their role in insecticide resistance. The sheep blowfly, Lucilia cuprina is a major economic problem for the sheep meat and wool industries in Australasia and hence this thesis has attempted the study of the Lucilia cuprina GST family, using proteomics, with a view to eventually determining their role in insecticide resistance. Combinations of different affinity matrices (glutathione-Sepharose matrix (GSH) followed by dinitrophenyl-glutathione-Sepharose matrix (DNP-GSH)) and two-dimensional electrophoresis has successfully isolated members from major four insect GST classes: Sigma, Delta, Epsilon and Omega. Drosophila melanogaster has been used as a model insect throughout as a basis for comparison. To characterise Lucilia GSTs, the whole metazoan fragmentation database was used for sequence alignment with Lucilia peptides. This approach is broad and speculative but predicts a possible classification of the GSTs based on % similarity and % identity. This method of characterisation yielded match scores that provided a basis for classification, which must at present be regarded as tentative and in need of confirmation. In D. melanogaster and L. cuprina, GSH affinity-purified extracts showed the presence of only Sigma and Delta GSTs. In D. melanogaster, the DNP-GSH affinity-purified GSTs showed mostly the presence of Epsilon and Omega GSTs whereas in L. cuprina no Omega GSTs were detected. In both species, the migration pattern of Delta GST on 2D PAGE gel indicated possible post-translational modification. The results from analysis of LC-MS/MS data by the software PEAKS suggested deamidation at asparagine and glutamine residues in a limited number of the matched peptides of Delta GST. GST activity was present in all developmental stages of L. cuprina. The number of isoenzymes and their extent of expression vary as the insect develops. Delta GSTs were present in all developmental stages. The Sigma GST started expressing from the larval stage and was abundantly present in adult stage. The DNP-GSH affinity matrix purified GSTs which have been tentatively classified as Mu-like GSTs were present in egg, larvae and pupae but totally absent in adult stage. The GST families were characterised by proteomics in the main body sections of L. cuprina. Higher GST activity towards 1-chloro-2, 4-dinitrobenzene (CDNB) was found in the thorax (65.2 %) followed by the abdomen (19.6%) and the head (15.2%). The cytosolic GSTs of a resistant strain (PY81) of L. cuprina had significantly higher (2.26- and 2.6- fold) activity than the susceptible strains (NSW and CSIRO) towards CDNB and 2, 3-dichloro, 4-nitrobenzene (DCNB) respectively. The proteomic analysis of DNP-GSH purified extract from susceptible and resistant strains showed quantitatively higher expression of GSTs on 2D PAGE gel of the PY81 strain. The in vitro interaction of purified GSTs and model insecticides studied by high performance liquid chromatography revealed that Delta and DNP-GSH affinity-purified GSTs catalyse the conjugation of the insecticides to reduced glutathione but Sigma GST had almost no activity.</p>

Comparative two-dimensional fluorescence gel electrophoresis

Comparative two-dimensional gel electrophoresis (CoFGE) is a special version of two-dimensional polyacrylamide GE (2D-PAGE) and related to difference GE (2D-DIGE). It provides reproducibility and standardisation for 2D-PAGE by introducing a reference to the experiment. CoFGE uses different fluorescent labels to distinguish analyte and a marker protein mixture. The method allows in silico correction of the assignment of gel-separated proteins based on the co-run references, which form a grid of landmarks across the entire gel. The variability of spot coordinates is reduced to ~1% error and data can thus be compared to results generated independently with the same method. In this way, searchable repositories of gel-separated proteins become feasible. In addition, the CoFGE experimental principle can be used for protein quantification by applying the proteins of the marker grid in different concentrations. Here we present the protocol for conducting a CoFGE experiment, which takes about 2 days to complete for a technician skilled in GE.

Hypoxia-Responsive Class III Peroxidases in Maize Roots: Soluble and Membrane-Bound Isoenzymes

Flooding induces low-oxygen environments (hypoxia or anoxia) that lead to energy disruption and an imbalance of reactive oxygen species (ROS) production and scavenging enzymes in plants. The influence of hypoxia on roots of hydroponically grown maize (Zea mays L.) plants was investigated. Gene expression (RNA Seq and RT-qPCR) and proteome (LC–MS/MS and 2D-PAGE) analyses were used to determine the alterations in soluble and membrane-bound class III peroxidases under hypoxia. Gel-free peroxidase analyses of plasma membrane-bound proteins showed an increased abundance of ZmPrx03, ZmPrx24, ZmPrx81, and ZmPr85 in stressed samples. Furthermore, RT-qPCR analyses of the corresponding peroxidase genes revealed an increased expression. These peroxidases could be separated with 2D-PAGE and identified by mass spectrometry. An increased abundance of ZmPrx03 and ZmPrx85 was determined. Further peroxidases were identified in detergent-insoluble membranes. Co-regulation with a respiratory burst oxidase homolog (Rboh) and key enzymes of the phenylpropanoid pathway indicates a function of the peroxidases in membrane protection, aerenchyma formation, and cell wall remodeling under hypoxia. This hypothesis was supported by the following: (i) an elevated level of hydrogen peroxide and aerenchyma formation; (ii) an increased guaiacol peroxidase activity in membrane fractions of stressed samples, whereas a decrease was observed in soluble fractions; and (iii) alterations in lignified cells, cellulose, and suberin in root cross-sections.

Protocols for the Detection and Proteome Analysis of the Yellow Mosaic Virus Infected Soyabean Leaves

Soybean (Glycine max) is one of the legumes, susceptible to yellow mosaic disease caused by Mungbean yellow mosaic India virus (MYMIV) and Mungbean yellow mosaic virus (MYMV) infection. The quantitative proteomic analysis allows achieving deeper knowledge about the viral infection. For quantitative proteomic analysis, two-dimensional gel electrophoresis (2D-PAGE) is the common method of choice. Optimization is required even for the published protocols based on the type of sample to be analyzed and for the proteins of interest. We compared four different published protocols with some modifications and selected the one which is more effective in terms of resolution and reproducibility of 2D-PAGE. Here we present our simple and cost-effective procedure for the detection of viral infection and proteomic analysis of YMV infected soybean leaves without compromising the resolution and reproducibility of 2D-PAGE.

HDL Particle Measurement: Comparison of 5 Methods

BACKGROUND HDL cell cholesterol efflux capacity has been documented as superior to HDL cholesterol (HDL-C) in predicting cardiovascular disease risk. HDL functions relate to its composition. Compositional assays are easier to perform and standardize than functional tests and are more practical for routine testing. Our goal was to compare measurements of HDL particles by 5 different separation methods. METHODS HDL subfractions were measured in 98 samples using vertical auto profiling (VAP), ion mobility (IM), nuclear magnetic resonance (NMR), native 2-dimensional gel electrophoresis (2D-PAGE), and pre-β1-ELISA. VAP measured cholesterol in large HDL2 and small HDL3; IM measured particle number directly in large, intermediate, and small HDL particles; NMR measured lipid signals in large, medium, and small HDL; 2D-PAGE measured apolipoprotein (apo) A-I in large (α1), medium (α2), small (α3–4), and pre-β1 HDL particles; and ELISA measured apoA-I in pre-β1-HDL. The data were normalized and compared using Passing–Bablok, Lin concordance, and Bland–Altman plot analyses. RESULTS With decreasing HDL-C concentration, NMR measured a gradually lower percentage of large HDL, compared with IM, VAP, and 2D-PAGE. In the lowest HDL-C tertile, NMR measured 8% of large HDL, compared with IM, 22%; VAP, 20%; and 2D-PAGE, 18%. There was strong discordance between 2D-PAGE and NMR in measuring medium HDL (R2 = 0.356; rc = 0.042) and small HDL (R2 = 0.376; rc = 0.040). The 2D-PAGE assay measured a significantly higher apoA-I concentration in pre-β1-HDL than the pre-β1-ELISA (9.8 vs 1.6 mg/dL; R2 = 0.246; rc = 0.130). CONCLUSIONS NMR agreed poorly with the other methods in measuring large HDL, particularly in low HDL-C individuals. Similarly, there was strong discordance in pre-β1-HDL measurements between the ELISA and 2D-PAGE assays.