Phosphorylation of phosphatidylinositol associated with the nicotinic acetylcholine receptor of Torpedo californica |
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Authors: | R Kiehl M Varsányi E Neumann |
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Affiliation: | 1. Department of Biochemistry and Molecular Biology, University of Chicago, Gordon Center for Integrative Science, 929 E 57th St, Chicago 60637 IL, United States;2. Department of Biophysics, Faculty of Science, Cairo University, Giza 12613, Egypt;3. School of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian 116029, China;1. Laboratorio de Oceanografía Biológica (CADIC-CONICET), Ushuaia, Argentina;2. Laboratorio de Microbiología Ambiental (IBIOMAR-CONICET), Puerto Madryn, Argentina |
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Abstract: | When isolated, detergent solubilized and affinity chromatographically purified nicotinic acetylcholine receptor of Torpedo californica electric organ is incubated with [gamma-32P]ATP/Mg2+, phosphatidylinositol 4-phosphate (PIP) is formed from receptor associated phosphatidylinositol (PI). This receptor associated endogenous kinase activity is enhanced by orthovanadate and, remarkably, also by acetylcholine. Exogenously added PI-kinase only increases the phosphorylation rate if vanadate is present. PIP as the main phosphorylation product (up to 95%) remains bound to the beta-, gamma- and delta-subunits of the receptor and to the receptor associated v-protein. The alpha-subunits do not carry 32p phosphate; no phosphatidylinositol 4,5-bisphosphate formation has been observed. Concomitant to lipid phosphorylation tyrosine and serine residues are phosphorylated (5% of total incorporated 32P phosphate). |
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