Fesselin binds to actin and myosin and inhibits actin-activated ATPase activity

Abstract

Fesselin is an actin binding protein that bundles actin filaments and accelerates nucleation of actin polymerization. The effect of fesselin on actin polymerization is regulated by Ca(++)-calmodulin. Because actin filaments serve both structural and contractile functions we also examined the effect of fesselin on activation of myosin S1 ATPase activity. Fesselin inhibited the activation of S1-catalyzed ATP hydrolysis in a similar manner in both the presence and absence of tropomyosin. This inhibition was unaffected by Ca(++)-calmodulin. Fesselin inhibited the binding of myosin-S1 to actin during steady-state ATP hydrolysis. Fesselin also displaced caldesmon from actin. S1 displaced fesselin from actin in the absence of nucleotide when the affinity of S1 for actin was much greater than the affinity of fesselin for actin. It is likely that fesselin and S1 share common binding sites on F-actin. We also observed that fesselin could bind to smooth muscle myosin with muM affinity. Fesselin shares some similarities to caldesmon in binding to several other proteins and having multiple potential functions.

Synaptopodin family of natively unfolded, actin binding proteins: physical properties and potential biological functions

“…In contrast, the affinity of Ca 2+ -calmodulin-synaptopodin 2 to F-actin remained high (∼10 8 M −1 ) (Schroeter and Chalovich 2004) and Ca 2+ -calmodulin did not reverse inhibition of actin-S1 ATPase activity by avian synaptopodin 2 (Schroeter and Chalovich 2005). A model of the synaptopodin 2 stimulated polymerization of actin is shown in Fig.…”

“…Synaptopodin 2 binds to smooth muscle myosin with an affinity of about 2×10 6 M −1 (50 mM ionic strength, pH 7, 10°C) (Schroeter and Chalovich 2005). Each myosin molecule bound to 2 molecules of synaptopodin 2; the myosin head groups appeared to be involved in the binding.…”

Various Themes of Myosin Regulation

“…In contrast, the actin binding protein fesselin stabilizes smooth muscle myosin-2 filaments and increases filament length and thickness. Fesselin also decreases the rate of actomyosin dissociation in the presence of ATP and inhibits the actin-activation of the myosin ATPase activity in a concentration-dependent and tropomyosinindependent manner with an IC 50 of 0.6 µM [189, 190]. …”

Localization of the actin-binding protein fesselin in chicken smooth muscle

“…While Ca 2+ -calmodulin regulates the interaction of fesselin with G-actin it has little effect on its interaction with F-actin (Schroeter and Chalovich 2004). Fesselin also inhibits the actin activation of S1 ATPase activity (Schroeter and Chalovich 2005). …”

“…Furthermore fesselin binds to several actin binding proteins including myosin (Schroeter and Chalovich 2005) and α-actinin (Pham and Chalovich 2006). Western blots using crude polyclonal antibody revealed fesselin expression in mammalian smooth, skeletal and cardiac muscle tissues.…”