Definition of a Ca2(+)-sensitive interface in the plasma gelsolin-actin complex.

Gelsolin is a Ca2(+)-dependent protein which severs actin filaments, caps their fast-growing ends and promotes nucleation. We report here results that delimit one of the interfaces between serum gelsolin and actin monomer. An actin-derived synthetic peptide (amino acids 305-326 of actin) coupled to a hydrophilic resin was tested for its possible interaction with gelsolin. We selected this sequence because it corresponds to a region implicated in the gelsolin-actin complex in a previous work [Boyer, Feinberg, Hue, Capony, Benyamin & Roustan (1987) Biochem. J. 248, 359-364]. We showed that this actin sequence is located at the surface of the actin molecule and observed a Ca2(+)-sensitive binding of gelsolin to this actin-derived peptide. In addition, by using a chymotryptic digest of gelsolin, we reported that only the C-terminal half of gelsolin interacts with the actin-(305-326)-peptide. These results that the Ca2(+)-sensitive interface includes both amino acids 305-326 of actin and probably amino acids 660-738 of gelsolin.