Calponin actomyosin ATPase inhibition

B. Inhibition of Actomyosin ATPase and in Vitro iMotility by Calponin... 

The mode of inhibition of actomyosin ATPase by calponin differs from that of caldesmon. The effect is mainly on the Vmax with only minor effects on the Km (Nishida et al. 1990, Horiuchi and Chacko 1991). Calponin is shown to affect strongly bound myosin (EL-Mezgueldi and Marston 1996, Borovikov et al. 1996). The inhibition is not dependent on tropomyosin (Winder and Walsh 1990) and the effects of calponin are due to changes in the actin conformation (Noda et al. 1992, Borovikov et al. 1996). 

To account for activation of arterial smooth muscle independently of LC20 phosphorylation, attention has been focused on the possible roles of the thin filament-associated regulatory proteins, caldesmon and calponin. Both proteins have been localized in the actomyosin domain of the smooth muscle cell and both have been shown to inhibit actin-activated myosin ATPase by interacting with F-actin, tropomyosin, and/or myosin (Clark et al., 1986 Takahashi et al.,... 

---