Study of the low molecular weight GTP binding proteins in amylase exocytosis of parotid acini in vitro.

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The trimeric GTP binding protein plays it as information and/or transformation factor on the plasma membranes. But existence of low molecular weight GTP binding protein which expressed in cytosol fraction. Futhermore, it is inserted in the secretory granule membranes in secretory cell and as member of constitution. So, low molecular weight GTP binding protein in parotid acinar cell exists in secretory granule membranes, and is which associated with amylase secretion. We examined whether playd it. Secretory granules of rat parotid glands were isolated by percoll-gradient centrifuges as described by Hopfer et al. We report here that at least 21ow molecular GTP-binding proteins (21 kD-25 kD) are associated with the plasma membrane and secretory granule membranes from rat parotid acini by [32 [-GTP overlay assay.Results1. The secretory granules isolated by rat parotid tissues. Western blotting analysis of the rho proteins. The rho protein A and B localized the plasma menbranes and secretory granule membranes as molecular weight at 21 kD.2. Inactivation of rho p21 of parotid acini by ADP-rybosiltransferase C3 resulted in the inhibited release of amylase, suggesting that amylase secretion was mediated by rho p21.