P-glycoprotein ATPase from the resistant pest, Helicoverpa armigera: Purification, characterization and effect of various insecticides on its transport function |
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| Authors: | Ravindra M Aurade Kuruba Sreeramulu |
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| Affiliation: | a Department of Biochemistry, Gulbarga University, Gulbarga 585106, India
b Agricultural Research Station, University of Agricultural Sciences, Gulbarga 585103, India |
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| Abstract: | Helicoverpa armigera is a major pest of agricultural crops and has developed resistance to various insecticides. A P-glycoprotein (Pgp) with ATPase activity likely to be involved in insecticide resistance was purified and characterized from insecticide-resistant H. armigera. The purification was 18-fold with 3% yield. The optimum pH and temperature were found to be 7.4 and 30-40 °C, respectively. Kinetic studies indicated that this enzyme had a Km value of 1.2 mM for ATP. Pgp from H. armigera was partially sequenced and found to be homologous to conserved sequences of mammalian Pgps. Pesticides stimulated H. armigera Pgp ATPase activity with a maximum stimulation of up to 40%. Quenching of the intrinsic tryptophan fluorescence of purified Pgp was used to quantitate insecticide binding. Using the high-affinity fluorescent substrate, tetramethylrosamine, transport was monitored in real time in proteoliposomes containing H. armigera Pgp. The presence of Pgp could be one of the reasons for insecticide resistance in this pest. |
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| Keywords: | ABC ATP-binding cassette CHAPS 3[(3-cholamidopropyl) dimethylammonio]-propanesulfonic acid DMPC l-α-phosphatidylcholine" target="_blank">dimyristoyl-l-α-phosphatidylcholine DTT dithiothreitol Ha-Pgp Helicoverpa armigera P-glycoprotein MDR multidrug resistance/resistant NBD nucleotide-binding domain Pgp P-glycoprotein p-NPP p-nitrophenylphosphate PMSF phenylmethanesulfonyl fluoride TMD transmembrane domain TMR tetramethylrosamine |
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