Fesselin is a target protein for calmodulin in a calcium-dependent manner

Fesselin is a basic protein isolated from smooth muscle which binds G-actin and accelerates its polymerization as well as cross-links assembled filaments [J. Muscle Res. Cell Motil. 20 (1999) 539; Biochemistry 40 (2001) 14252]. In this report experimental evidence is provided for the first time proving that fesselin can interact with calmodulin in a Ca(2+)-dependent manner in vitro. Using ion exchange, followed by calmodulin-affinity chromatography, enabled us to simplify and shorten the fesselin preparation procedure and increase its yield by about three times in comparison to the procedure described by Leinweber et al. [J. Muscle Res. Cell Motil. 20 (1999) 539]. Fesselin interaction with dansyl-labelled calmodulin causes a 2-fold increase in maximum fluorescence intensity of the fluorophore and a 21nm blue shift of the spectrum. The transition of complex formation between fesselin and calmodulin occurs at submicromolar concentration of calcium ions. The dissociation constant of fesselin Ca(2+)/calmodulin complexes amounted to 10(-8)M. The results suggest the existence of a direct link between Ca(2+)/calmodulin and fesselin at the level of actin cytoskeleton dynamics in smooth muscle.