title: Self-association of chicken gizzard filamin and heavy merofilamin.
abstract: Filamin is a high molecular weight (subunit Mr 250 000) actin-binding protein isolated from smooth muscle. The protein forms a gel when mixed with solutions of F-actin. A proteolytic fragment of filamin, heavy merofilamin (subunit Mr 240 000), generated by the action of Ca2+-activated protease binds to actin but does not produce gelation. We have studied the self-association properties of filamin and heavy merofilamin by direct examination in the electron microscope and by equilibrium sedimentation distribution studies in the ultracentrifuge. Filamin self-associates reversibly to form dimers; the free energy of dimerization is approximately 7 kcal/mol. Further association to form tetramer and multimer appears to be irreversible. Warming of filamin solutions accelerates aggregation. Heavy merofilamin does not appear to self-associate but is entirely monomeric. These studies suggest that filamin produces gelation of F-actin by binding to actin and then self-associating to cross-link actin filaments into a gel.
mesh_terms: D000818:Animals; D002645:Chickens; D003285:Contractile Proteins / Q000378:metabolism*; D064448:Filamins; D005782:Gels; D005895:Gizzard, Avian / Q000032:analysis*; D008433:Mathematics; D008840:Microfilament Proteins; D008854:Microscopy, Electron; D008954:Models, Biological; D008970:Molecular Weight; D011485:Protein Binding; D013696:Temperature; D014461:Ultracentrifugation
chemical_list: D003285:Contractile Proteins; D064448:Filamins; D005782:Gels; D008840:Microfilament Proteins