Interaction between Cdc42Hs and RhoGDI is mediated through the Rho insert region.
Members of the Rho subfamily of GTP-binding proteins contain a region of amino acid sequence (residues 122-134) that is absent from other Ras-like proteins and is termed the Rho insert region. To address the functional role of this domain, we have constructed a Cdc42Hs/Ras chimera in which loop 8 from Ha-Ras was substituted for the region in Cdc42Hs that contains the 13-amino acid insert region. Our data indicate that the insert region of Cdc42Hs is not essential for its interactions with various target/effector molecules or for interactions with the guanine nucleotide exchange factor, Dbl, or the Cdc42 GTPase-activating protein (GAP). However, the regulation of GDP dissociation and GTP hydrolysis on Cdc42Hs by the Rho GDP-dissociation inhibitor (GDI) is extremely sensitive to changes in the insert region, such that a Cdc42Hs/Ha-Ras chimera that lacks this insert is no longer susceptible to a GDI-induced inhibition of GDP dissociation and GTP hydrolysis. The insensitivity to GDI activity is not due to the inability of the GDI molecule to bind to the Cdc42Hs/Ha-Ras chimera, and in fact, the GDI is fully capable of stimulating the release of this chimera from membranes.
Wu
W J
WJ
Department of Pharmacology, Veterinary Medical Center, Cornell University, Ithaca, New York 14853, USA.
Leonard
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A-Cerione
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D000595:Amino Acid Sequence; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020730:Guanine Nucleotide Dissociation Inhibitors; D008969:Molecular Sequence Data; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D020764:cdc42 GTP-Binding Protein; D018631:ras Proteins / Q000235:genetics; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors
D018797:Cell Cycle Proteins; D020730:Guanine Nucleotide Dissociation Inhibitors; D011993:Recombinant Fusion Proteins; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020764:cdc42 GTP-Binding Protein; D018631:ras Proteins