Instability of F-actin in the absence of ATP: a small amount of myosin destabilizes F-actin.
The effects of the neutral salt concentration, pH, and coexistence of myosin on the denaturation of F-actin without ATP at low temperature were studied using the DNase I inhibition assay. The percent denaturation of F-actin gradually increased with a decrease in pH from 8.0 to 5.2, on incubation for 2 weeks in the presence of 50 mM KCl at 0 degrees C. This change was much faster in 0.5 M KCl and more than 75% of the F-actin became denatured on incubation for 1 week at pH 5.2. The buffer composition was found to exert a strong influence on the denaturation of F-actin. That is, there was a tendency for the denaturation of F-actin at pH 6.0 to be faster in MES[2-(N-morpholino)ethanesulfonic acid]-NaOH buffer than in sodium phosphate buffer, the critical concentrations of actin in 0.5 M KCl being 0.31 mg/ml for MES-NaOH buffer and 0.15 mg/ml for sodium phosphate buffer. A sigmoidal relationship was found between the percent denaturation of F-actin and the KCl concentration added, the greatest change occurring at KCl concentrations between 0.25 and 0.75 M. The time courses of the denaturation of F-actin showed that the percent denaturation rose at first and that in time the rate of the increase decreased. In the case of pH 8.0 and 0.5 M KCl, it took about 1 week for the denaturation rate to begin to drop. The pH of 6.0 further promoted the instability of F-actin exposed to high KCl concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)
Ikeuchi
Y
Y
Department of Applied Biological Chemistry, Faculty of Agriculture, Niigata University.
Iwamura
K
K
Machi
T
T
Kakimoto
T
T
Suzuki
A
A
D000199:Actins / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D015879:Myosin Subfragments / Q000378:metabolism*; D011189:Potassium Chloride; D011489:Protein Denaturation; D011817:Rabbits
D000199:Actins; D015879:Myosin Subfragments; D011189:Potassium Chloride; D000255:Adenosine Triphosphate