InterPro domain: IPR000406

The GDP dissociation inhibitor for rho proteins, rho GDI, regulates GDP/GTP exchange by inhibiting the dissociation of GDP from them. The protein contains 204 amino acids, with a calculated Mr value of 23,421. Hydropathy analysis shows it to be largely hydrophilic, with a single hydrophobic region. Results of database searches suggest rho GDI is a novel protein, currently with no known homologue. The protein plays an important role in the activation of the superoxide (O2-)-generating NADPH oxidase of phagocytes. This process requires the interaction of membrane-associated cytochrome b559 with 3 cytosolic components: p47-phox, p67-phox and a heterodimer of the small G-protein p21rac1 and rho GDI [ 1 ]. The association of p21rac and GDI inhibits dissociation of GDP from p21rac, thereby maintaining it in an inactive form. The proteins are attached via a lipid tail on p21rac that binds to the hydrophobic region of GDI [ 2 ]. Dissociation of these proteins might be mediated by the release of lipids (e.g., arachidonate and phosphatidate) from membranes through the action of phospholipases [ 3 ]. The lipids may then compete with the lipid tail on p21rac for the hydrophobic pocket on GDI.

1. Role of the rac1 p21-GDP-dissociation inhibitor for rho heterodimer in the activation of the superoxide-forming NADPH oxidase of macrophages. Eur. J. Biochem. 217, 441-55
2. The NADPH oxidase and chronic granulomatous disease. null 2, 129-35