title: Mouse class III myosins: kinase activity and phosphorylation sites.
abstract: As class III unconventional myosins are motor proteins with an N-terminal kinase domain, it seems likely they play a role in both signaling and actin based transport. A growing body of evidence indicates that the motor functions of human class IIIA myosin, which has been implicated in progressive hearing loss, are modulated by intermolecular autophosphorylation. However, the phosphorylation sites have not been identified. We studied the kinase activity and phosphorylation sites of mouse class III myosins, mMyo3A and 3B, which are highly similar to their human orthologs. We demonstrate that the kinase domains of mMyo3A and 3B are active kinases, and that they have similar, if not identical, substrate specificities. We show that the kinase domains of these proteins autophosphorylate, and that they can phosphorylate sites within their myosin and tail domains. Using liquid chromatography-mass spectrometry, we identified phosphorylated sites in the kinase, myosin motor and tail domains of both mMyo3A and 3B. Most of the phosphorylated sites we identified and their consensus phosphorylation motifs are highly conserved among vertebrate class III myosins, including human class III myosins. Our findings are a major step toward understanding how the functions of class III myosins are regulated by phosphorylation.
authors: Department of Molecular and Cell Biology, University of California, Berkeley, California, USA.
authors: Jasbir S
authors: JS
authors: Dalal
authors: Stanley M
authors: SM
authors: Stevens
authors: Sophie
authors: S
authors: Alvarez
authors: Nathalie
authors: N
authors: Munoz
authors: Karen E
authors: KE
authors: Kempler
authors: Andrea C
authors: AC
authors: Dosé
authors: Beth
authors: B
authors: Burnside
authors: Barbara-Anne
authors: BA
authors: Battelle
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids; D000818:Animals; D006801:Humans; D013058:Mass Spectrometry; D051379:Mice; D025102:Myosin Type III / Q000737:chemistry* / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D020539:Sequence Analysis, Protein; D013379:Substrate Specificity
chemical_list: D000596:Amino Acids; D010455:Peptides; D011994:Recombinant Proteins; D011494:Protein Kinases; D025102:Myosin Type III