title: p140Sra-1 (specifically Rac1-associated protein) is a novel specific target for Rac1 small GTPase.
abstract: Rac1 small GTPase plays pivotal roles in various cell functions such as cell morphology, cell polarity, and cell proliferation. We have previously identified IQGAP1 from bovine brain cytosol as a target for Rac1 by an affinity purification method. By using the same method, we purified a specifically Rac1-associated protein with a molecular mass of about 140 kDa (p140) from bovine brain cytosol. This protein interacted with guanosine 5'-(3-O-thio)triphosphate (GTPgammaS).glutathione S-transferase (GST)-Rac1 but not with the GDP.GST-Rac1, GTPgammaS.GST-Cdc42, or GTPgammaS.GST-RhoA. The amino acid sequences of this protein revealed that p140 is identified as a product of KIAA0068 gene. We denoted this protein as Sra-1 (Specifically Rac1-associated protein). Recombinant Sra-1 interacted with GTPgammaS.GST-Rac1 and weakly with GDP.Rac1 but not with GST-Cdc42 or GST-RhoA. The N-terminal domain of Sra-1 (1-407 amino acids) was responsible for the interaction with Rac1. Myc-tagged Sra-1 and the deletion mutant capable of interacting with Rac1, but not the mutants unable to bind Rac1, were colocalized with dominant active Rac1(Val-12) and cortical actin filament at the Rac1(Val-12)-induced membrane ruffling area in KB cells. Sra-1 was cosedimented with filamentous actin (F-actin), indicating that Sra-1 directly interacts with F-actin. These results suggest that Sra-1 is a novel and specific target for Rac1.
authors.affiliation: Division of Signal Transduction, Nara Institute of Science and Technology, Ikoma 630-01, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kobayashi
authors.forename: S
authors.initials: S
authors.lastname: Kuroda
authors.forename: M
authors.initials: M
authors.lastname: Fukata
authors.forename: T
authors.initials: T
authors.lastname: Nakamura
authors.forename: T
authors.initials: T
authors.lastname: Nagase
authors.forename: N
authors.initials: N
authors.lastname: Nomura
authors.forename: Y
authors.initials: Y
authors.lastname: Matsuura
authors.forename: N
authors.initials: N
authors.lastname: Yoshida-Kubomura
authors.forename: A
authors.initials: A
authors.lastname: Iwamatsu
authors.forename: K
authors.initials: K
authors.lastname: Kaibuchi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D019204:GTP-Binding Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity; D020744:rac GTP-Binding Proteins
chemical_list: D002352:Carrier Proteins; D011994:Recombinant Proteins; D019204:GTP-Binding Proteins; D020744:rac GTP-Binding Proteins