A Conserved Binding Motif Defines Numerous Candidate Target Proteins for Both Cdc42 and Rac GTPases

doi:10.1074/jbc.270.49.29071

A Conserved Binding Motif Defines Numerous Candidate Target Proteins for Both Cdc42 and Rac GTPases (*)

From the Medical Research Council Laboratory for Molecular Cell Biology, CRC Oncogene and Signal Transduction Group, London WC1E 6BT, United Kingdom
Department of Biochemistry, University College London, London WC1E 6BT, United Kingdom

^¶To whom correspondence should be addressed. Tel.: 44-171-380-7909; Fax: 44-171-380-7805.

Abstract

Rho, Rac, and Cdc42 are small GTPases that regulate the formation of a variety of actin structures and the assembly of associated integrin complexes, but little is known about the target proteins that mediate their effects. Here we have used a motif-based search method to identify putative effector proteins for Rac and Cdc42. A search of the GenBank data base for similarity with the minimum Cdc42/Rac interactive binding (CRIB) region of a potential effector protein p65 has identified over 25 proteins containing a similar motif from a range of different species. These candidate Cdc42/Rac-binding proteins include family members of the mixed lineage kinases (MLK), a novel tyrosine kinase from Drosophila melanogaster (DPR2), a human protein MSE55, and several novel yeast and Caenorhabditis elegans proteins. Two murine p65 isoforms and a candidate protein from C. elegans, F09F7.5, interact strongly with the GTP form of both Cdc42 and Rac, but not Rho in a filter binding assay. Three additional candidate proteins, DPR2, MSE55, and MLK3 showed binding to the GTP form of Cdc42 and weaker binding with Rac, and again no interaction with Rho. These results indicate that proteins containing the CRIB motif bind to Cdc42 and/or Rac in a GTP-dependent manner, and they may, therefore, participate in downstream signaling.

Footnotes

↵^§ Supported by a Hitchings-Elion Fellowship from the Wellcome Trust.
↵(*) This work was supported in part by the Cancer Research Campaign (to A. H.) and the Wellcome Trust (to A. H. and D. D.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

GAP

GTPase-activating protein

GST

glutathione S-transferase

MLK

mixed-lineage kinase

PCR

polymerase chain reaction.
↵²P. D. Burbelo, D. Drechsel, and A. Hall, manuscript in preparation.
- Received August 3, 1995.