Crosslinking of F-actin by a bifunctional reagent glutaraldehyde resulted in a marked decrease of viscosity and length of F-actin filaments. The extent and rate of superprecipitation of actomyosin reconstituted from the modified actin were lower than those of unmodified actin-myosin complex, but activation of heavy meromyosin ATPase by the crosslinked actin was higher than by unmodified one. Heavy meromyosin ATPase activated by the crosslinked actin was distinctly less dependent on KCl concentration than that activated by unmodified actin. Turbidity of the modified acto-heavy meromyosin in the presence of ATP exceeded the sum of turbidities of actin and heavy meromyosin, whereas in the case of unmodified acto-heavy meromyosin the turbidity was comparable to that for noninteracting system. The difference in activation of heavy meromyosin ATPase by the crosslinked and unmodified actin, clearly seen at room temperature, significantly diminished when temperature was lowered to 0°C.
Bibliographical noteFunding Information:
The author is indebted to prof. F. Oosawa for helpful discussions and reading of the manuscript, to Dr. F. Matsumura from Nagoya University for taking electron microscopic pictures and to Dr. T. Yanagida and the staff of the Department of Biophysical Engineering of Osaka University for their hospitality. The author expresses also her thanks to Dr. H. Strzelecka-Golaszewska and to prof. W. Drabikowski from Nencki Institute of Experimental Biology for their interest and help in preparation of the manuscript. This work was supported by a grant from Japan Society for Promotion of Sciences.
- Heavy meromyosin
- Protein-protein interaction