title: Isolation of a 5-kilodalton actin-sequestering peptide from human blood platelets.
abstract: Resting human platelets contain approximately 0.3 mM unpolymerized actin. When freshly drawn and washed platelets are treated with saponin, 85-90% of the unpolymerized actin diffuses out. Analysis by polyacrylamide gel electrophoresis under nondenaturing conditions shows that the bulk of this unpolymerized actin migrates with a higher mobility than does pure G-actin, profilactin, or actin-gelsolin complex. When muscle G-actin is added to fresh or boiled saponin extract, the added muscle actin is shifted to the high-mobility form. The saponin extract contains an acidic peptide having a molecular mass in the range of 5 kDa, which has been purified to homogeneity by reverse-phase HPLC. This peptide also shifts muscle actin to the high-mobility form. Addition of either boiled saponin extract or the purified peptide to muscle G-actin also strongly and stoichiometrically inhibits salt-induced polymerization, as assayed by falling-ball viscometry and by sedimentation. We conclude that this peptide binds to the bulk of the unpolymerized actin in platelets and prevents it from polymerizing.
authors.affiliation: Department of Anatomy, School of Medicine, University of Pennsylvania, Philadelphia 19104-6058.
authors.forename: D
authors.initials: D
authors.lastname: Safer
authors.forename: R
authors.initials: R
authors.lastname: Golla
authors.forename: V T
authors.initials: VT
authors.lastname: Nachmias
mesh_terms: D000199:Actins / Q000097:blood*; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D015151:Immunoblotting; D007700:Kinetics; D046911:Macromolecular Substances; D008840:Microfilament Proteins / Q000097:blood* / Q000302:isolation & purification; D008970:Molecular Weight; D009132:Muscles / Q000378:metabolism; D009218:Myosins / Q000378:metabolism; D011817:Rabbits
chemical_list: D000199:Actins; D000596:Amino Acids; D046911:Macromolecular Substances; D008840:Microfilament Proteins; D009218:Myosins