A novel type of regulatory protein for the GDP/GTP exchange reaction of smg p25A, a ras p21-like small GTP-binding protein, in bovine brain cytosol.
A regulatory protein for smg p25A, a ras p21-like small GTP-binding protein, was purified to near homogeneity from bovine brain cytosol. This regulatory protein, named smg p25A GDP dissociation inhibitor (GDI), regulated the GDP/GTP exchange reaction of smg p25A by inhibiting the dissociation of GDP from and the subsequent binding of GTP to it. Both the GDP- and GTP-bound forms of smg p25A bound to synaptic plasma membranes and vesicles. smg p25A GDI formed a complex with the GDP-bound form of smg p25A and thereby inhibited its binding to membranes and furthermore induced the dissociation of the prebound protein from the membranes. These results indicate that smg p25A GDI is a novel type of regulatory protein for the GDP/GTP exchange reaction and the intracellular translocation of smg p25A.
Sasaki
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Department of Biochemistry, Kobe University School of Medicine.
D000818:Animals; D001923:Brain Chemistry; D002417:Cattle; D003600:Cytosol / Q000737:chemistry; D019204:GTP-Binding Proteins / Q000302:isolation & purification* / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism*; D007700:Kinetics; D013570:Synaptic Membranes / Q000378:metabolism; D013572:Synaptic Vesicles / Q000378:metabolism; D020692:rab3 GTP-Binding Proteins
D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D020692:rab3 GTP-Binding Proteins