Identification of G-proteins in rat parotid gland plasma membranes and granule membranes: presence of distinct components in granule membranes |
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Authors: | Nawab Ali Devendra K Agrawal Peter Cheung |
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Institution: | (1) Department of Internal Medicine Creighton, University School of Medicine, 2500 California Street, 68178 Omaha, NE, USA |
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Abstract: | We have identified by immunoblotting and ADP-ribosylation by cholera toxin and pertussis toxin the presence of Mr 43 and 46 KDa Gs, and 39 and 41 KDa Gi;.. subunits in rat parotid gland plasma membranes but not in granule membranes. A Mr 28 KDa polypeptide that served as substrate for ADP-ribosylation by both cholera toxin and pertussis toxin was present exclusively in granule membranes. Photoaffinity crosslinking of -32P]GTP showed the presence of high molecular weight GTP-binding proteins (Mr 160,100 KDa) in granule membranes. Six low molecular weight GTP-binding proteins (Mr 21–28 KDa) were differentially distributed in both plasma membranes and granule membranes. The present study identifies various GTP-binding proteins in rat parotid gland plasma membranes and granule membranes, and demonstrates the presence of distinct molecular weight GTP-binding proteins in granule membranes. These granule-associated GTP-binding proteins may be involved in secretory processes. |
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Keywords: | G-proteins parotid gland exocytosis granule membranes ADP ribosylation |
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