Identification of myosin III as a protein kinase.
Drosophila ninaC gene encodes myosin homologous proteins which are classified as myosin III of the myosin superfamily, yet the physiological and biochemical function of myosin III has not characterized. We report here that myosin III does exhibit protein kinase activity. The kinase homologous domain (MYOIIIPK) of myosin III was expressed in the baculovirus expression system and purified to homogeneity. MYOIIIPK phosphorylated a number of proteins including myosin III p132 and smooth muscle myosin regulatory light chain (LC20), suggesting that myosin III is a multifunctional protein kinase. The phosphoamino acid analysis revealed that myosin III is a serine/threonine kinase but not a tyrosine kinase. The observation that MYOIIIPK phosphorylates myosin III suggests that the autophosphorylation might play a role for the regulation of myosin III function. This is the first direct demonstration of kinase activity for the myosin III class.
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Department of Biology, Case Western Reserve University, Cleveland, Ohio 44106, USA.
Kambara
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Matsuura
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Burke
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Ikebe
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D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002852:Chromatography, Ion Exchange; D003001:Cloning, Molecular; D004330:Drosophila; D029721:Drosophila Proteins; D004591:Electrophoresis, Polyacrylamide Gel; D005136:Eye Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D015636:Magnesium Chloride / Q000494:pharmacology; D008969:Molecular Sequence Data; D008970:Molecular Weight; D018995:Myosin Heavy Chains / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology; D013379:Substrate Specificity
D029721:Drosophila Proteins; D005136:Eye Proteins; D015636:Magnesium Chloride; D012965:Sodium Chloride; D000255:Adenosine Triphosphate; D011494:Protein Kinases; C072308:ninaC protein, Drosophila; D018995:Myosin Heavy Chains