The Rho family of small GTPases and their associated regulators and targets are essential mediators of diverse morphogenetic events in development. Mammalian Rho-kinase/ROKa, one of the targets of Rho, has been shown to bind to Rho in GTP-bound form and to phosphorylate the myosin light chain (MLC) and the myosin-binding subunit (MBS) of myosin phosphatase, resulting in the activation of myosin. Thus, Rho-kinase/ROKa has been suggested to play essential roles in the formation of stress fibers and focal adhesions. We have identified the Drosophila homolog of Rho-kinase/ROKa, DRho-kinase, which has conserved the basic structural feature of Rho-kinase/ROKa consisting of the N-terminal kinase, central coiled-coil and C-terminal pleckstrin homology (PH) domains. A two-hybrid analysis demonstrated that DRho-kinase interacts with the GTP-bound form of the Drosophila Rho, Drho1, at the conserved Rho-binding site. DRho-kinase can phosphorylate MLC and MBS, preferable substrates for bovine Rho-kinase, in vitro. DRho-kinase is ubiquitously expressed throughout development, in a pattern essentially identical to that of Drho1. These results suggest that DRho-kinase is an effector of Drho1. (C) 1999 Elsevier Science B.V. All rights reserved.
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