p140Sra-1 (specifically Rac1-associated protein) is a novel specific target for Rac1 small GTPase

Kenta Kobayashi, Shinya Kuroda, Masaki Fukata, Tomoko Nakamura, Takahiro Nagase, Nobuo Nomura, Yoshiharu Matsuura, Nobuko Yoshida-Kubomura, Akihiro Iwamatsu, Kozo Kaibuchi

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185 Citations (Scopus)


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 (GTPγS)-glutathione S-transferase (GST)-Rac1 but not with the GDP·GST-Rac1, GTPγS·GST-Cdc42, or GTPγS·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 GTPγS·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.

Original languageEnglish
Pages (from-to)291-295
Number of pages5
JournalJournal of Biological Chemistry
Issue number1
Publication statusPublished - 02-01-1998
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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