ACTIN-BINDING PROTEIN IN HUMAN PLATELETS - INTERACTIONS WITH ALPHA-ACTININ ON GELATIN OF ACTIN AND INFLUENCE OF CYTOCHALASIN-B

  • 1 January 1978
    • journal article
    • research article
    • Vol. 93  (2) , 433-446
Abstract
A protein (MW, approximately 250,000) with actin-binding properties was isolated from human platelets. Addition of the actin-binding protein (ABP) to semiviscous solutions of purified actin containing troponin-tropomyosin (TM-TP) complex resulted in formation of viscous gels consisting of randomly associated actin TM-TP filaments. .alpha.-Actinin (.alpha.A), a muscle protein recently detected in platelets, induced random cross-linking of dissociated actin into gels. Sequential addition of ABP and .alpha.A resulted in gels consisting of parallel associated actin TM-TP filaments in bundles, suggesting a cooperative interaction. Cytochalasin B (CB) had no apparent effect on the cross-linking of randomly associated actin TM-TP filaments induced by either protein alone but prevented development of bundles of parallel filaments when ABP and .alpha.A were added sequentially. CB disrupted the bundles of parallel associated actin TM-TP filaments when added to gels already formed by the dual action of ABP and .alpha.A and caused simultaneous release of .alpha.A from the complexes to the supernatant. Platelet ABP and .alpha.A may induce actin filaments to form the parallel associations observed in platelet pseudopods.