Dinitrophenylation of rabbit skeletal actomyosin.
Dinitrophenylated reconstituted or natural actomyosin effected changes in the Ca2+ sensitivity which were dependent upon the ionic strength of the reaction medium. Dinitrophenylation of reconstituted actomyosin in 0.6 M KCl led to the incorporation of 2-6 mol of the reagent per 5-10(5) g of protein and it possessed considerable Ca2+ sensitivity. Dinitrophenylated natural actomyosin under the same conditions lost most of its Ca2+ sensitivity when 1.3-5.4 mol of the dinitrophenyl group were bound. The myosin from these modified actomyosins did not lose Ca2+ sensitivity and the myosin was labeled only with 0.4-1.7 mol of the dinitrophenyl group. Dinitrophenylation of both kinds of actomyosin in 0.06 M KCl abolished the Ca2+ sensitivity; the myosin from the modified actomyosins also lost Ca2+ sensitivity. Myosin alone was more susceptible to a loss of Ca2+ sensitivity than myosin in actomyosin. Actin protected the ability of myosin to sense Ca2+ regulated actin in modified actomyosin at 0.6 M KCl but not at 0.06 M KCl. Actomyosin dinitrophenylated in the presence of ATP lost Ca2+ sensitivity. However, the myosin from this actomyosin possessed Ca2+ sensitivity. Thiolysis of the dinitrophenylated actomyosin by 2-mercaptoethanol at low ionic strength did not restore the Ca2+ sensitivity of this actomyosin or its myosin although there was a significant loss of the dinitrophenyl group.
D000205:Actomyosin / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000494:pharmacology; D004139:Dinitrofluorobenzene; D004591:Electrophoresis, Polyacrylamide Gel; D007700:Kinetics; D008623:Mercaptoethanol; D009132:Muscles / Q000032:analysis; D009218:Myosins / Q000378:metabolism; D009578:Nitrobenzenes; D009994:Osmolar Concentration; D011189:Potassium Chloride / Q000494:pharmacology; D011485:Protein Binding; D011817:Rabbits; D013997:Time Factors; D014335:Tropomyosin
D009578:Nitrobenzenes; D014335:Tropomyosin; D008623:Mercaptoethanol; D011189:Potassium Chloride; D000205:Actomyosin; D004139:Dinitrofluorobenzene; D009218:Myosins; D002118:Calcium