title: Characterization of rhoGAP. A GTPase-activating protein for rho-related small GTPases.
abstract: GTPase-activating proteins or GAPs play an important role in signal transduction pathways regulated by GTP-binding proteins. In addition to acting as down-regulators of GTPases, there is growing evidence that they also act as effector molecules required for downstream signaling. PLC-beta 1, the target protein regulated by the heterotrimeric GTPase Gq, has been shown to be a GAP, whereas rasGAP, a down-regulator of the small GTPase ras, may be required for the ras-mediated signals. We have purified a GAP specific for the rho subfamily of small GTPases. Partial sequence analysis of rhoGAP has led to the identification of a family of related proteins which now includes bcr, chimaerin, p190, p85, and 3BP-1. We report here the isolation of a cDNA clone encoding human rhoGAP and the expression of recombinant protein. The full-length protein is 50 kDa and is ubiquitously expressed in mammalian cells. At least three members of the rho family are substrates for rhoGAP, rho, rac, and G25K/CDC42, and they each bind equally well to the protein. In vitro GTPase assays, however, reveal that G25K/CDC42 is the preferred substrate. RhoGAP contains a proline-rich sequence, suggesting that it is an SH3-binding protein.
authors.affiliation: Chester Beatty Laboratories, Institute of Cancer Research, London, United Kingdom.
authors.forename: C A
authors.initials: CA
authors.lastname: Lancaster
authors.forename: P M
authors.initials: PM
authors.lastname: Taylor-Harris
authors.forename: A J
authors.initials: AJ
authors.lastname: Self
authors.forename: S
authors.initials: S
authors.lastname: Brill
authors.forename: H E
authors.initials: HE
authors.lastname: van Erp
authors.forename: A
authors.initials: A
authors.lastname: Hall
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D015153:Blotting, Western; D003001:Cloning, Molecular; D017931:DNA Primers / Q000737:chemistry; D018076:DNA, Complementary; D019204:GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D015870:Gene Expression; D006801:Humans; D008969:Molecular Sequence Data; D011506:Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D020703:ras GTPase-Activating Proteins
chemical_list: D017931:DNA Primers; D018076:DNA, Complementary; D020690:GTPase-Activating Proteins; D011506:Proteins; D012333:RNA, Messenger; D020703:ras GTPase-Activating Proteins; C085379:rho GTPase-activating protein; D019204:GTP-Binding Proteins