title: A platelet inhibitor protein with cytochalasin-like activity against actin polymerization in vitro.
abstract: We have obtained an inhibitor fraction containing cytochalasin-like activity from human platelets. Using a procedure involving DEAE-cellulose, hydroxyapatite and gel filtration column chromatography, we obtained a fraction from human platelets which apparently can compete with 3H--cytochalasin B for binding to spectrin-actin complexes from human erythrocytes. The inhibitor activity is nondialyzable, sensitive to heat and to trypsin and has a Stoke's radius of 40 A. This fraction stops nuclei-induced actin polymerization in 0.4 mM MgCl2 and reduces the viscosity of F actin to that of G actin, which suggests depolymerization of the filaments. These results suggest that the inhibitor fraction contains a protein which interacts with actin filaments and nuclei in a manner similar to that of cytochalasin B. It is possible that such a protein is involved in the control of cell motility by affecting assembly and disassembly of actin-containing microfilaments in vivo.
mesh_terms: D000199:Actins / Q000378:metabolism*; D001665:Binding Sites; D001792:Blood Platelets / Q000032:analysis*; D001798:Blood Proteins / Q000302:isolation & purification / Q000494:pharmacology*; D003571:Cytochalasin B / Q000378:metabolism; D004912:Erythrocytes; D006801:Humans; D011108:Polymers; D013049:Spectrin / Q000378:metabolism
chemical_list: D000199:Actins; D001798:Blood Proteins; D011108:Polymers; D013049:Spectrin; D003571:Cytochalasin B