title: Comparison of the effects of calponin and a 38-kDa caldesmon fragment on formation of the "strong-binding" state in ghost muscle fibers.
abstract: We studied the conformational changes in actin filaments induced by the binding of calponin or a 38-kDa fragment of caldesmon, two actin-binding proteins known to inhibit actin-activated ATP hydrolysis by phosphorylated smooth muscle myosin. The F-actinin myosin-free muscle fibers (ghost fibers) was labeled with fluorescein-5-maleimide and the conformational change in actin was determined by polarized fluorimetry. Data show that both calponin and the 38-kDa caldesmon fragment inhibit the conformational changes in F-actin that are compatible with the "strong-binding" state between myosin heads and actin. Tropomyosin slightly reduced the effect produced by calponin, but enhances the effect produced by the 38-kDa caldesmon fragment.
authors.affiliation: Institute of Cytology RAS, St. Petersburg, Russia.
authors.forename: Y S
authors.initials: YS
authors.lastname: Borovikov
authors.forename: M I
authors.initials: MI
authors.lastname: Khoroshev
authors.forename: S
authors.initials: S
authors.lastname: Chacko
mesh_terms: D000199:Actins / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D002135:Calcium-Binding Proteins / Q000378:metabolism* / Q000494:pharmacology; D002148:Calmodulin-Binding Proteins / Q000378:metabolism* / Q000494:pharmacology; D002645:Chickens; D003432:Cross-Linking Reagents / Q000494:pharmacology; D005033:Ethylmaleimide / Q000494:pharmacology; D005895:Gizzard, Avian; D008301:Maleimides / Q000494:pharmacology; D008840:Microfilament Proteins; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D009124:Muscle Proteins / Q000378:metabolism / Q000494:pharmacology; D018482:Muscle, Skeletal / Q000502:physiology*; D009130:Muscle, Smooth / Q000502:physiology; D009218:Myosins / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology; D011485:Protein Binding; D011487:Protein Conformation; D011817:Rabbits; D000096985:Calponins
chemical_list: D000199:Actins; D002135:Calcium-Binding Proteins; D002148:Calmodulin-Binding Proteins; D003432:Cross-Linking Reagents; D005033:Ethylmaleimide; D008301:Maleimides; D008840:Microfilament Proteins; D009124:Muscle Proteins; D009218:Myosins; D010446:Peptide Fragments; D000096985:Calponins