title: Biochemical and bioinformatic analysis of the myosin-XIX motor domain.
abstract: Mitochondrial dynamics are dependent on both the microtubule and actin cytoskeletal systems. Evidence for the involvement of myosin motors has been described in many systems, and until recently a candidate mitochondrial myosin transport motor had not been described in vertebrates. Myosin-XIX (MYO19) was predicted to represent a novel class of myosin and had previously been shown to bind to mitochondria and increase mitochondrial network dynamics when ectopically expressed. Our analyses comparing ∼40 MYO19 orthologs to ∼2000 other myosin motor domain sequences identified instances of homology well-conserved within class XIX myosins that were not found in other myosin classes, suggesting MYO19-specific mechanochemistry. Steady-state biochemical analyses of the MYO19 motor domain indicate that Homo sapiens MYO19 is a functional motor. Insect cell-expressed constructs bound calmodulin as a light chain at the predicted stoichiometry and displayed actin-activated ATPase activity. MYO19 constructs demonstrated high actin affinity in the presence of ATP in actin-co-sedimentation assays, and translocated actin filaments in gliding assays. Expression of GFP-MYO19 containing a mutation impairing ATPase activity did not enhance mitochondrial network dynamics, as occurs with wild-type MYO19, indicating that myosin motor activity is required for mitochondrial motility. The measured biochemical properties of MYO19 suggest it is a high-duty ratio motor that could serve to transport mitochondria or anchor mitochondria, depending upon the cellular microenvironment.
authors.affiliation: Program in Biochemistry, Mount Holyoke College, South Hadley, Massachusetts, USA.
authors.forename: Rebecca C
authors.initials: RC
authors.lastname: Adikes
authors.forename: William C
authors.initials: WC
authors.lastname: Unrath
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Yengo
authors.forename: Omar A
authors.initials: OA
authors.lastname: Quintero
mesh_terms: D000199:Actins / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002147:Calmodulin / Q000378:metabolism; D045744:Cell Line, Tumor; D019295:Computational Biology; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D008969:Molecular Sequence Data; D009218:Myosins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary
chemical_list: D000199:Actins; D002147:Calmodulin; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D009218:Myosins