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Scinderin is a Ca²⁺-dependent actin filament severing protein present in a variety of secretory cells. Previous work suggests that scinderin-evoked cortical F-actin disassembly is required for secretion because local disassembly of cortical cytoskeleton allows secretory vesicle exocytosis (Vitale, M. L., Rodrı́guez Del Castillo, A., Tchakarov, L., and Trifaró, J.-M. (1991) J. Cell Biol. 113, 1057–1067). Scinderin has six domains each containing three internal sequence motifs, two actin, and two phosphatidylinositol disphosphate-binding sites in domains 1 and 2. In this paper we report the presence of another actin-binding site at the NH₂-terminal of domain 5 (Sc^511–518). This site binds actin in a Ca²⁺-independent manner and a recombinant fragment (Sc5–6 or Sc^502–715) containing this site binds to actin-DNase-I-Sepharose 4B beads, co-sediments with actin and is able to nucleate actin assembly. Recombinant Sc_L …