Lack of GTP-bound Rho1p in secretory vesicles of Saccharomyces cerevisiae.
Rho1p, an essential Rho-type GTPase in Saccharomyces cerevisiae, activates its effectors in the GTP-bound form. Here, we show that Rho1p in secretory vesicles cannot activate 1,3-beta-glucan synthase, a cell wall synthesizing enzyme, during vesicular transport to the plasma membrane. Analyses with an antibody preferentially reacting with the GTP-bound form of Rho1p revealed that Rho1p remains in the inactive form in secretory vesicles. Rom2p, the GDP/GTP exchange factor of Rho1p, is preferentially localized on the plasma membrane even when vesicular transport is blocked. Overexpression of Rom2p results in delocalization of Rom2p and accumulation of 1,3-beta-glucan in secretory vesicles. Based on these results, we propose that Rho1p is kept inactive in intracellular secretory organelles, resulting in repression of the activity of the cell wall-synthesizing enzyme within cells.[1]References
- Lack of GTP-bound Rho1p in secretory vesicles of Saccharomyces cerevisiae. Abe, M., Qadota, H., Hirata, A., Ohya, Y. J. Cell Biol. (2003) [Pubmed]
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