title: Fluorescence anisotropy of labeled F-actin: influence of divalent cations on the interaction between F-actin and myosin heads.
abstract: The interaction between F-actin and soluble proteolytic fragments of myosin, heavy meromyosin and myosin subfragment 1 without ATP, has been studied by measuring the static anisotropy and the transient anisotropy decay of the fluorescent chromophore N-(iodoacetyl)-N'-(5-sulfo-1-naphthyl) ethylenediamine bound to F-actin. In the presence of Ca2+ ions, the mobility of the chromophore was strongly decreased by adding heavy meromyosin or myosin subfragment 1, and this conformation change of F-actin showed a strong cooperativity; that is, a very small amount of myosin heads induced the maximum anisotropy change. On the other hand, in the presence of Mg2+ ions, the addition of a small amount of myosin subfragment 1 or of heavy meromyosin increased the mobility of labeled F-actin that reached a maximum at a molar ratio of about 1/25 or 1/50, respectively. With further addition of myosin heads, the mobility of the labeled actin decreased. From these studies, one concludes that F-actin undergoes a conformation change by interacting with myosin heads, which depends on the nature of the divalent cations present in the solution.
mesh_terms: D000199:Actins / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D005454:Fluorescence Polarization; D005456:Fluorescent Dyes; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology*; D009132:Muscles / Q000378:metabolism; D015879:Myosin Subfragments; D009218:Myosins / Q000378:metabolism*; D009282:Naphthalenesulfonates; D010446:Peptide Fragments / Q000378:metabolism; D011487:Protein Conformation; D011817:Rabbits
chemical_list: D000199:Actins; D005456:Fluorescent Dyes; D015879:Myosin Subfragments; D009282:Naphthalenesulfonates; D010446:Peptide Fragments; C006421:1,5-I-AEDANS; D000251:Adenosine Triphosphatases; D009218:Myosins; D008274:Magnesium; D002118:Calcium