PT  - JOURNAL ARTICLE
AU  - Matsunaga, Kimihiro
AU  - Nakatani, Keigo
AU  - Murakami, Masahiro
AU  - Yamaguchi, Katsumi
AU  - Ohizumi, Yasushi
TI  - Powerful Activation of Skeletal Muscle Actomyosin ATPase by Goniodomin A Is Highly Sensitive to Troponin/Tropomyosin Complex
DP  - 1999 Dec 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 1121--1126
VI  - 291
IP  - 3
4099  - http://jpet.aspetjournals.org/content/291/3/1121.short
4100  - http://jpet.aspetjournals.org/content/291/3/1121.full
SO  - J Pharmacol Exp Ther1999 Dec 01; 291
AB  - Goniodomin A has been shown to cause the conformational change of actin to modify actomyosin ATPase activity. Goniodomin A induced a potent stimulation of the actomyosin ATPase activities of the actin-myosin reconstituted system and natural actomyosin in the range of 10−8 to 10−7 M. When the concentration was increased above 10−7 M, actomyosin ATPase activity was decreased. Interestingly, the troponin/tropomyosin complex caused a concentration-dependent inhibition of the goniodomin A-induced stimulation of actomyosin ATPase activity. In the presence of a high concentration of the troponin/tropomyosin complex, goniodomin A decreased actomyosin ATPase activity in a concentration-dependent manner. The enhancement of the ATPase activity of troponin/tropomyosin-free natural actomyosin by goniodomin A was larger than that obtained with natural actomyosin. Goniodomin A at lower concentrations enhanced the superprecipitation of natural actomyosin but decreased it at higher concentrations. The ATPase activity of skeletal muscle myofibrils and the contractile response of skinned fibers to Ca2+ were never activated and were decreased by this compound, suggesting an inhibition by the troponin/tropomyosin complex. In the far ultraviolet circular dichroism, goniodomin A above 10−8 M increased the negative ellipticity at 220 nm, suggesting an increase in the α-helical content of actin. These results suggest that goniodomin A increases and decreases actomyosin ATPase activity, probably through the stimulatory and inhibitory sites on actin, respectively. It is also suggested that the troponin/tropomyosin complex binds to actin to inhibit the goniodomin A-induced enhancement of actomyosin ATPase activity, probably by affecting the stimulatory site on the molecule. The American Society for Pharmacology and Experimental Therapeutics