title: Interaction of calponin with actin and its functional implications.
abstract: Titration of F-actin with calponin causes the formation of two types of complexes. One, at saturation, contains a lower ratio of calponin to actin (0.5:1) and is insoluble at physiological ionic strength. The another is soluble, with a higher ratio of calponin to actin (1:1). Electron microscopy revealed that the former complex consists of paracrystalline bundles of actin filaments, whereas the latter consists of separate filaments. Ca(2+)-calmodulin causes dissociation of bundles with simultaneous increase in the number of separate calponin-containing filaments. Further increase in the calmodulin concentration results in full release of calponin from actin filaments. In motility assays, calponin, when added together with ATP to actin filaments complexed with immobilized myosin, evoked a decrease in both the number and velocity of moving actin filaments. Addition of calponin to actin filaments before their binding to myosin resulted in a formation of actin filament bundles which were dissociated by ATP.
authors.affiliation: Department of Muscle Biochemistry, Nencki Institute of Experimental Biology, Warsaw, Poland.
authors.forename: J
authors.initials: J
authors.lastname: Kołakowski
authors.forename: R
authors.initials: R
authors.lastname: Makuch
authors.forename: D
authors.initials: D
authors.lastname: Stepkowski
authors.forename: R
authors.initials: R
authors.lastname: Dabrowska
mesh_terms: D000199:Actins / Q000187:drug effects / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000378:metabolism* / Q000494:pharmacology; D002147:Calmodulin / Q000494:pharmacology; D002645:Chickens; D004591:Electrophoresis, Polyacrylamide Gel; D008840:Microfilament Proteins; D008854:Microscopy, Electron; D009218:Myosins / Q000378:metabolism; D009994:Osmolar Concentration; D011817:Rabbits; D014461:Ultracentrifugation; D000096985:Calponins
chemical_list: D000199:Actins; D000255:Adenosine Triphosphate; D002118:Calcium; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D008840:Microfilament Proteins; D009218:Myosins; D000096985:Calponins