title: Reversible binding of actin to gelsolin and profilin in human platelet extracts.
abstract: This paper documents the reversible appearance of high-affinity complexes of profilin and gelsolin with actin in extracts of platelets undergoing activation and actin assembly. Sepharose beads coupled to either monoclonal anti-gelsolin antibodies or to polyproline were used to extract gelsolin and profilin, respectively, from EGTA-containing platelet extracts and determine the proportion of these molecules bound to actin with sufficient affinity to withstand dilution (high-affinity complexes). Resting platelets (incubated for 30 min at 37 degrees C after gel filtration) contained nearly no high-affinity actin/gelsolin or actin/profilin complexes. Thrombin, within seconds, caused quantitative conversion of platelet profilin and gelsolin to high-affinity complexes with actin, but these complexes were not present 5 min after stimulation. The calcium-dependent actin filament-severing activity of platelet extracts, a function of free gelsolin, fell in concert with the formation of EGTA-stable actin/gelsolin complexes, and rose when the adsorption experiments indicated that free gelsolin was restored. The dissociation of high-affinity complexes was temporally correlated with the accumulation of actin in the Triton-insoluble cytoskeleton.
mesh_terms: D000199:Actins / Q000097:blood*; D000596:Amino Acids / Q000032:analysis; D001792:Blood Platelets / Q000378:metabolism*; D001798:Blood Proteins; D002135:Calcium-Binding Proteins / Q000097:blood*; D003285:Contractile Proteins / Q000097:blood*; D004533:Egtazic Acid; D018260:Gelsolin; D006801:Humans; D046911:Macromolecular Substances; D008840:Microfilament Proteins / Q000097:blood*; D008970:Molecular Weight; D051304:Profilins; D011485:Protein Binding
chemical_list: D000199:Actins; D000596:Amino Acids; D001798:Blood Proteins; D002135:Calcium-Binding Proteins; D003285:Contractile Proteins; D018260:Gelsolin; D046911:Macromolecular Substances; D008840:Microfilament Proteins; C495738:PFN1 protein, human; D051304:Profilins; D004533:Egtazic Acid