Interaction of RhoA GTPase with its effector p160Rock

Radovan DVORSKY¹, Lars BLUMENSTEIN¹, Mohammad R. AHMADIAN¹

¹ Max-Planck-Institute of Molecular Physiology, Department Structural Biology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany

The GTP-binding proteins (or Rho-GTPases) of the Rho-family regulate a variety of cellular processes in all eukaryotic cells, ranging from cytoskeletal reorganization and cell motility to gene transcription in response to external stimuli [1]. To date, 19 different mammalian Rho-GTPases have been identified from which Cdc42, Rac1 and RhoA are the most extensively characterised members of the Rho-family. The function of Rho-GTPases depends on the guanine nucleotide-bound state. As molecular switches Rho-GTPases cycle between an inactive GDP-bound state and an active GTP-bound state, which is controlled by numerous cellular proteins. Active form of Rho-GTPases interact with their downstream targets, so-called effector proteins, that are responsible for the diverse biological effects of Rho-GTPases [2]. One of the best studied Rho-Effectors, the Ser/Thr kinase p160Rock, plays a key role in actin–myosin filament assembly by activation of signalling molecules involved in various biological processes [3].

We will present the structure of the complex of RhoA GTPase with the Rho-binding domain of p160Rock. We found that the switching regions of RhoA molecule interacts with C-terminal part of parallel coiled-coil formed by Rho-binding domains. Such an arrangement of the complex will be discussed with respect to the general switching mechanism of GTPases and their interaction with downstream effectors.

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2. A. L. Bishop & A. Hall, Biochem J. 348 (2000) 241-255.

3. M. Amano, Y. Fukata & K. Kaibuchi, Exp Cell Res. 261 (2000) 44-51.