Cloning and characterization of a Dictyostelium myosin I heavy chain kinase activated by Cdc42 and Rac.
The motile activities of the small, single-headed class I myosins (myosin I) from the lower eukaryotes Acanthamoeba and Dictyostelium are activated by phosphorylation of a single serine or threonine residue in the head domain of the heavy chain. Recently, we purified a myosin I heavy chain kinase (MIHCK) from Dictyostelium based on its ability to activate the Dictyostelium myosin ID isozyme (Lee, S. -F., and Côté, G. P. (1995) J. Biol. Chem. 270, 11776-11782). The complete sequence of the Dictyostelium MIHCK has now been determined, revealing a protein of 98 kDa that is composed of an amino-terminal domain rich in proline, glutamine, and serine, a putative Cdc42/Rac binding motif, and a carboxyl-terminal kinase catalytic domain. MIHCK shares significant sequence identity with the Saccharomyces cerevisiae Ste20p kinase and the mammalian p21-activated kinase. Gel overlay assays and affinity chromatography experiments showed that MIHCK interacted with GTPgammaS (guanosine 5'-3-O-(thiotriphosphate))-labeled Cdc42 and Rac1 but not RhoA. In the presence of GTPgammaS-Rac1 MIHCK autophosphorylation increased from 1 to 9 mol of phosphate/mol, and the rate of Dictyostelium myosin ID phosphorylation was stimulated 10-fold. MIHCK may therefore provide a direct link between Cdc42/Rac signaling pathways and motile processes driven by myosin I molecules.
Department of Biochemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada.
S F
SF
Lee
T T
TT
Egelhoff
A
A
Mahasneh
G P
GP
Côté
D000595:Amino Acid Sequence; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000737:chemistry / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism*; D003001:Cloning, Molecular; D004023:Dictyostelium / Q000201:enzymology*; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism*; D008969:Molecular Sequence Data; D015800:Protozoan Proteins; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae; D020744:rac GTP-Binding Proteins
D018797:Cell Cycle Proteins; D007527:Isoenzymes; D015800:Protozoan Proteins; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C033142:myosin-heavy-chain kinase; D019204:GTP-Binding Proteins; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae; D020744:rac GTP-Binding Proteins