Biology

Chimeric analysis of the small GTPase RacE in cytokinesis signaling in Dictyostelium discoideum

Document Type

Article

Abstract

RacE is a small GTPase required for cytokinesis in Dictyostelium discoideum. To investigate RacE's potential binding and signaling interfaces that allow its function in cytokinesis, 10 different chimeras were created between RacE and the closely related small GTPase, RacC. RacE/RacC chimeras, containing various combinations of four RacE regions, E I-IV: E-I (aa 1-67), E-II (aa 68-124), E-III (aa 125-184), and E-IV (aa 185-223), were tested for their ability to rescue the multinucleated, cytokinesis-defective phenotype of RacE null cells grown in suspension. Regions E-II and E-IV were essential but not sufficient for the rescue of RacE null cells. These two regions, in combination with either region E-1 or E-III, resulted in rescue. Results presented here suggest that region E-II contains a crucial, yet incomplete, binding site. Regions E-I or E-III separately provide additional, necessary elements for RacE's function. The extended E tail of RacE (E-IV) may act as a 'sensor' of the bound nucleotide state of RacE and facilitate GDP to GTP exchange (possibly through interactions with a GEF molecule), thereby resulting in activation of RacE. This study provides new evidence for small GTPases engaging several distinct protein interfaces to mediate signaling in various cellular processes. © 2004 Elsevier Inc. All rights reserved.

Publication Title

Experimental Cell Research

Publication Date

4-15-2004

Volume

295

Issue

1

First Page

226

Last Page

235

ISSN

0014-4827

DOI

10.1016/j.yexcr.2004.01.001

Keywords

Chimera, cytokinesis, effector, GTPase, insertion, polybasic domain, RacC, RacE

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