The DH-PH region of the giant protein UNC-89 activates RHO-1 GTPase in Caenorhabditis elegans body wall muscle |
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Authors: | Qadota Hiroshi Blangy Anne Xiong Ge Benian Guy M |
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Affiliation: | 1 Department of Pathology, Emory University, Atlanta, Georgia 30322 2 CRBM CNRS UMR5237, 1919 route de Mende, 34293 Montpellier cedex 5, France 3 Graduate Division of Biological and Biomedical Sciences, Emory University, Atlanta, Georgia 30322 |
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Abstract: | Mutation of the Caenorhabditis elegans gene unc-89 results in disorganization of muscle A-bands. unc-89 encodes a giant polypeptide (900 kDa) containing a DH domain followed by a PH domain at its N terminus, which is characteristic of guanine nucleotide exchange factor proteins for Rho GTPases. To obtain evidence that the DH-PH region has activity toward specific Rho family small GTPases, we conducted an experiment using the yeast three-hybrid system. The DH-PH region of UNC-89 has exchange activity for RHO-1 (C. elegans RhoA), but not for CED-10 (C. elegans Rac), MIG-2 (C. elegans RhoG), or CDC-42 (C. elegans Cdc42). The DH domain alone has similar activity for RHO-1. An in vitro binding assay demonstrates interaction between the DH-PH region of UNC-89 and each of the C. elegans Rho GTPases. Partial knockdown of rho-1 in C. elegans adults showed a pattern of disorganization of myosin thick filaments similar to the phenotype caused by unc-89 (su75), a mutant allele in which all of the isoforms containing the DH-PH region are missing. Taken together, we propose a model in which the DH-PH region of UNC-89 activates RHO-1 GTPase for organization of myosin filaments in C. elegans muscle cells. |
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Keywords: | GEF, guanine nucleotide exchange factor GAP, GTPase-activating protein MBP, maltose-binding protein MHC, myosin heavy chain GFP, green fluorescent protein |
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