title: Subunit flow in F-actin under steady-state conditions. Application of a novel method to determination of the rate of subunit exchange of F-actin at the terminals.
abstract: We developed a novel method to determine the subunit exchange rates of F-actin at its terminals under quasi-steady-state conditions by using a powerful fluorescent probe, N-(1-pyrenyl)iodoacetamide. The applicability of the method was checked with regard to both theoretical and experimental aspects. We determined the rates of subunit exchange of F-actin and F-actin-tropomyosin complex under various ionic conditions. We found that: (i) KCl accelerated both on and off rates at each end, and lowered the critical concentration of the P-end while the critical concentration of the B-end was not affected; (ii) binding of tropomyosin drastically reduced the subunit flow in F-actin by suppressing the off rate principally of the P-end. It is therefore believed that tropomyosin exerts an anisotropic constraint on F-actin and regulates its dynamic polarity.
authors.affiliation: Department of Physics, Faculty of Science, Nagoya University, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Suzuki
authors.forename: K
authors.initials: K
authors.lastname: Mihashi
mesh_terms: D000199:Actins / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D003571:Cytochalasin B / Q000378:metabolism; D007700:Kinetics; D046911:Macromolecular Substances; D008433:Mathematics; D008962:Models, Theoretical; D011485:Protein Binding; D013050:Spectrometry, Fluorescence / Q000379:methods; D014335:Tropomyosin / Q000378:metabolism
chemical_list: D000199:Actins; D046911:Macromolecular Substances; D014335:Tropomyosin; D003571:Cytochalasin B; D000251:Adenosine Triphosphatases