title: Filamin-actin interaction. Dissociation of binding from gelation by Ca2+-activated proteolysis.
abstract: Chicken gizzard filamin has been digested with purified Ca2+-activated protease. The subunits of (Mr = 250,000) of the protein are cleaved asymmetrically into two fragments, heavy merofilamin, Mr = 240,000, and light merofilamin, Mr = 9,500. Digestion is complete at substrate to enzyme ratios of 100:1 and requires Ca2+ concentrations in excess of 0.3 mM. Heavy merofilamin binds to F-actin as evidenced by cosedimentation with F-actin, by direct observation under the electron microscope, and by its ability to inhibit actin activation of heavy meromyosin ATPase. Heavy merofilamin does not form a gel when mixed with actin, except at very low concentrations of KCl. Thus, actin binding and gelation are separable activities of filamin. We speculate that Ca2+-stimulated proteolysis may play a role in the regulation of actin-filamin interactions.
mesh_terms: D000199:Actins / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002352:Carrier Proteins / Q000378:metabolism*; D002645:Chickens; D003285:Contractile Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D005782:Gels; D005895:Gizzard, Avian; D015879:Myosin Subfragments; D010446:Peptide Fragments; D010447:Peptide Hydrolases; D011485:Protein Binding
chemical_list: D000199:Actins; D002352:Carrier Proteins; D003285:Contractile Proteins; D005782:Gels; D015879:Myosin Subfragments; D010446:Peptide Fragments; D010447:Peptide Hydrolases; D000251:Adenosine Triphosphatases; D002118:Calcium