Desmin affects the sliding movement of actomyosins

Matsuda, A., Hatori, K.

Department of Bio-System Engineering, Yamagata University



Abstract
Desmin, which is one of the constituents of intermediate filaments, is widely found in various muscular tissues. Although desmin is thought to strengthen the cell structure, its functional roles in muscular contraction are unknown.
We examined effects of desmin molecules on the actomyosin function both in the superprecipitation of natural actomyosin suspension and in the motility assay. Skeletal muscular actin and myosin were employed in this study. Monomeric desmin was prepared from a chicken gizzard and was added to an assay solution just before experiments. In the superprecipitation experiments, desmin enhanced the contractile condensation of actomyosins in the presence of Ca ions. On the other hand, in the absence of Ca ions, desmin was more effective in suppressing superprecipitation. This results show that desmin may vary the binding strength between actin and myosin which were regulated by concentration of Ca ions. In the motility assay, sliding velocity of actin filaments on myosin molecules was decreased by 20 % with an increase of concentration of desmin in the range of 0 - 0.1 mg/ml. Also, the length of actin filaments during the movement was deceased with the increase of concentration of desmin.
Desmin was found to affect directly both the contraction of actomyosins and the sliding movement of actin filament on myosin molecules.