INTERACTION OF CALDESMON WITH PHOSPHOLIPIDS

The interaction of caldesmon with liposomes composed of various phosph olipids has been examined by tryptophan fluorescence spectroscopy. The results indicate that caldesmon makes its strongest complex with phos phatidylserine (PS) vesicles (K(ass) = 1.45 x 10(5) M-1). Both electro static and hydrophobic interactions contribute to the stability of thi s complex. The site for strong binding of PS seems to be located in th e N-terminal part of the 34 kDa C-terminal fragment of caldesmon. Bind ing of PS at this site results in displacement of calmodulin from its complex with caldesmon.