Myosin-IXb is a single-headed and processive motor.

Post PL, Tyska MJ, O'Connell CB, Johung K, Hayward A, Mooseker MS
J Biol Chem. 2002 277 (14): 11679-83

PMID: 11801597 · DOI:10.1074/jbc.M111173200

Class IX myosins are unique among the many classes of known actin-based motors in that the tail region of these myosins contains a GTPase-activating protein domain for the small GTP-binding protein, Rho. Previous studies on human myosin-IXb indicate that this myosin is mechanochemically active and exhibits actin-binding properties similar to the processive motor, myosin-Va. Motility analysis of antibody-tethered myosin-IXb performed using the sliding actin filament assay indicates that this myosin does exhibit properties characteristic of a processive motor. Like myosin-Va, the velocity of myosin-IXb remains constant (38.2 +/- 1.2 nm/s) even at single motor/filament densities. At low motor densities, filaments can be seen passing through and pivoting about single points on the motility surface. Analysis of filament landing rates as a function of motor density also indicates that a single motor is sufficient for filament movement. However, in contrast to myosin-Va, which uses coordinated motion of its two heads to move processively along the filament, hydrodynamic and chemical cross-linking studies indicate that under the conditions tested, myosin-IXb is a single-headed motor consisting of a single heavy chain and associated light chains.

MeSH Terms (14)

Cell Movement Cross-Linking Reagents Dose-Response Relationship, Drug Down-Regulation GTP Phosphohydrolases Humans Kinetics Leukocytes Microscopy, Fluorescence Myosin Heavy Chains Myosins Myosin Type V Signal Transduction Tumor Cells, Cultured

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