Ca2+-dependent regulation of the dynamic polarity of F-actin under the influence of tropomyosin and troponin.
A novel method that we have developed in the preceding paper to study the subunit exchange rates of F-actin (N. Suzuki and K. Mihashi, Biophys. Chem. 33 (1989) 177) was applied to regulated F-actin (a complex of F-actin, tropomyosin and troponin). We found that the dynamic polarity of regulated F-actin is modulated in a Ca2+-dependent manner, giving rise to strong suppression of the on/off rates of subunit exchange at the P-end. We interpreted this characteristic suppression as follows. Removal of Ca2+ from troponin C in regulated F-actin produces strong constraints on fluctuations in potential energy of an intermediate conformation of the terminal structure (P-end) which would be formed in the course of association and dissociation of the actin subunit.
Mihashi
K
K
Department of Physics, Faculty of Science, Nagoya University, Japan.
Suzuki
N
N
Ooi
A
A
D000199:Actins / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology*; D007700:Kinetics; D046911:Macromolecular Substances; D008433:Mathematics; D008962:Models, Theoretical; D014335:Tropomyosin / Q000378:metabolism*; D014336:Troponin / Q000378:metabolism*
D000199:Actins; D046911:Macromolecular Substances; D014335:Tropomyosin; D014336:Troponin; D002118:Calcium