High impact information on GDI1

• Here we explore the roles of the GDP and GTP states of Ypt7p using Gdi1p (which extracts Ypt7:GDP), Gyp7p (a GTPase-activating protein for Ypt7p:GTP), GTPgammaS or GppNHp (non-hydrolyzable nucleotides), and mutant forms of Ypt7p that favor either GTP or GDP states [1].
• GDP-bound Ypt7p on isolated vacuoles can be extracted by Gdi1p, although only the GTP-bound state allows docking [1].
• Soluble fractions prepared from temperature-sensitive mutants revealed requirements for the Ypt1p, Sec19p, Sly1p, Sec7p, and Uso1 proteins [2].
• The in vitro fusion reaction is inhibited either by Gdi1p, which extracts the GDP-bound form of ras-like GTPases from membranes, or by antibodies specific for Ypt7p [3].
• These results establish that Gdi1p plays an essential function in membrane traffic and are consistent with a role for Gdi1p in the recycling of proteins of the Sec4/Ypt/rab family from their target membranes back to their vesicular pools [4].

Biological context of GDI1

• The nucleotide sequences of 2.8 kb and 2.9 kb fragments containing the Kluyveromyces lactis and Pichia pastoris GDI1 genes, respectively, were determined [5].
• K. lactis GDI1 was found during sequencing of a genomic library clone, whereas the P. pastoris GDI1 was obtained from a genomic library by complementing a Saccharomyces cerevisiae sec19-1 mutant strain [5].
• Depletion of Gdi1p in vivo leads to loss of the soluble pool of Sec4p and inhibition of protein transport at multiple stages of the secretory pathway [4].

Anatomical context of GDI1

• In one gdi1 mutant, the cytosolic pools of all Rabs tested were depleted, and Rab accumulated on membranes, suggesting that this mutant Gdi1 protein has a general defect in extraction of Rab from membranes [6].
• The functionality of the OsGDIs was demonstrated by their ability to rescue the Sec19 mutant of Saccharomyces cerevisiae which is defective in vesicle transport [7].

Associations of GDI1 with chemical compounds

• Of particular interest are the Rab guanosine nucleotide diphosphate dissociation inhibitor proteins (Rab-GDI) which bind to prenylated Rab GTPases, slow the rate of GDP dissociation and escort GDP bound Rab proteins to their target membranes and retrieve them after completion of their catalytic cycle [8].
• This protein specifically binds guanine nucleotides and interacts via its C-terminal end with the unique Rab GDP Dissociation Inhibitor (RabGDI) [9].

Physical interactions of GDI1

• Structure of Rab GDP-dissociation inhibitor in complex with prenylated YPT1 GTPase [10].

Other interactions of GDI1

• Using an in vitro assay which reconstitutes Gdi1p-mediated membrane loading of Rab, this mutant Gdi1p was found to be defective in loading of Vps21p but not Ypt1p [6].
• We examined the relationship of GDI1 and DSS4 with SEC4 both genetically and biochemically [11].
• Analogous to the bovine protein, purified Gdi1p slows the dissociation of GDP from Sec4p and releases the GDP-bound form from yeast membranes [4].
• Thus, after priming, Vam7p is released from the vacuole altogether if Ypt7p has been extracted by Gdi1p or inactivated by antibody but is not released if docking is blocked simply by vacuole dilution; it is therefore Ypt7p function, and not docking per se, that retains Vam7p [12].
• Yip1p function requires Rab-GDI and Rab proteins, and several mutations that abrogate Yip1p function lack Rab-interacting capability [13].

Analytical, diagnostic and therapeutic context of GDI1

• Using site-directed mutagenesis of yeast GDI1, we demonstrate that amino acid residues required for Rab recognition in vitro are critical for function in vivo in Saccharomyces cerevisiae [14].

References