These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: The chemical mechanism of myosin-I: implications for actin-based motility and the evolution of the myosin family of motor proteins.
    Author: Pollard TD, Ostap EM.
    Journal: Cell Struct Funct; 1996 Oct; 21(5):351-6. PubMed ID: 9118240.
    Abstract:
    The Acanthamoeba myosin-IA and myosin-IB molecular motors bind to membranes, so they may produce the force to move organelles and membranes along actin filaments. We have determined the rate constants for the actin-activated myosin-I ATPase by pre-steady state kinetic analysis. ATP binds rapidly to myosin-I and dissociates the enzyme from actin filaments at a rate > 500 s-1. Myosin-I hydrolyzes ATP to ADP and inorganic phosphate (Pi) at 20-50 s-1. Phosphate dissociation is the rate limiting step in the ATPase cycle, 0.01 s-1 for myosin-I alone and at 10 s-1 when myosin-I is bound to actin filaments. ADP dissociation is rapid. Phosphorylation controls the ATPase cycle by increasing the rate of phosphate release from myosin-I bound to actin. At steady state the major species are myosin-ATP and myosin-ADP-Pi, which rapidly bind to and dissociate from actin filaments. During the ATPase cycle myosin-I binds so weakly to actin filaments that it cannot support processive movement like kinesin, unless several motors cluster together on a membrane or actin filament. These properties of the enzyme emphasize the importance of characterizing mechanisms that promote the self-association of myosin-I isoforms at specific binding sites in cells.
    [Abstract] [Full Text] [Related] [New Search]