The small GTP-binding protein Rho binds to and activates a 160 kDa Ser/Thr protein kinase homologous to myotonic dystrophy kinase.
The small GTP-binding protein Rho functions as a molecular switch in the formation of focal adhesions and stress fibers, cytokinesis and transcriptional activation. The biochemical mechanism underlying these actions remains unknown. Using a ligand overlay assay, we purified a 160 kDa platelet protein that bound specifically to GTP-bound Rho. This protein, p160, underwent autophosphorylation at its serine and threonine residues and showed the kinase activity to exogenous substrates. Both activities were enhanced by the addition of GTP-bound Rho. A cDNA encoding p160 coded for a 1354 amino acid protein. This protein has a Ser/Thr kinase domain in its N-terminus, followed by a coiled-coil structure approximately 600 amino acids long, and a cysteine-rich zinc finger-like motif and a pleckstrin homology region in the C-terminus. The N-terminus region including a kinase domain and a part of coiled-coil structure showed strong homology to myotonic dystrophy kinase over 500 residues. When co-expressed with RhoA in COS cells, p160 was co-precipitated with the expressed Rho and its kinase activity was activated, indicating that p160 can associate physically and functionally with Rho both in vitro and in vivo.
Ishizaki
T
T
Department of Pharmacology, Kyoto University Faculty of Medicine, Japan.
Maekawa
M
M
Fujisawa
K
K
Okawa
K
K
Iwamatsu
A
A
Fujita
A
A
Watanabe
N
N
Saito
Y
Y
Kakizuka
A
A
Morii
N
N
Narumiya
S
S
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D015394:Molecular Structure; D008970:Molecular Weight; D009223:Myotonic Dystrophy / Q000201:enzymology*; D065636:Myotonin-Protein Kinase; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014162:Transfection; D020741:rho GTP-Binding Proteins
C585517:DMPK protein, human; D017931:DNA Primers; D018076:DNA, Complementary; D065636:Myotonin-Protein Kinase; D017346:Protein Serine-Threonine Kinases; D019204:GTP-Binding Proteins; D020741:rho GTP-Binding Proteins