title: Dynacortin is a novel actin bundling protein that localizes to dynamic actin structures.
abstract: Dynacortin is a novel protein that was discovered in a genetic suppressor screen of a Dictyostelium discoideum cytokinesis-deficient mutant cell line devoid of the cleavage furrow actin bundling protein, cortexillin I. While dynacortin is highly enriched in the cortex, particularly in cell-surface protrusions, it is excluded from the cleavage furrow cortex during cytokinesis. Here, we describe the biochemical characterization of this new protein. Purified dynacortin is an 80-kDa dimer with a large 5.7-nm Stokes radius. Dynacortin cross-links actin filaments into parallel arrays with a mole ratio of one dimer to 1.3 actin monomers and a 3.1 microm K(d). Using total internal reflection fluorescence microscopy, GFP-dynacortin and the actin bundling protein coronin-GFP are seen to concentrate in highly dynamic cortical structures with assembly and disassembly half-lives of about 15 s. These results indicate that cells have evolved different actin-filament cross-linking proteins with complementary cellular distributions that collaborate to orchestrate complex cell shape changes.
authors.affiliation: Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305-5307, USA. Douglas.Robinson@jhu.edu
authors.forename: Douglas N
authors.initials: DN
authors.lastname: Robinson
authors.forename: Stephani S
authors.initials: SS
authors.lastname: Ocon
authors.forename: Ronald S
authors.initials: RS
authors.lastname: Rock
authors.forename: James A
authors.initials: JA
authors.lastname: Spudich
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D018797:Cell Cycle Proteins / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D002455:Cell Division; D004023:Dictyostelium / Q000737:chemistry; D008840:Microfilament Proteins / Q000032:analysis*; D011994:Recombinant Proteins / Q000302:isolation & purification
chemical_list: D000199:Actins; D018797:Cell Cycle Proteins; D008840:Microfilament Proteins; D011994:Recombinant Proteins; C413645:dct protein, Dictyostelium discoideum