title: Inhibition of actin-activated myosin Mg(2+)-ATPase in smooth muscle by ruthenium red.
abstract: Ruthenium red was found to inhibit actin-activated myosin Mg(2+)-ATPase in smooth muscle and to bind to myosin heavy chain, but not to F-actin. The inhibition by Ruthenium red of actin-activated Mg(2+)-ATPase was of the competitive type with respect to actin (Ki 4.4 microM) and of the non-competitive type with respect to ATP (Ki 6.6 microM). However, Ruthenium red scarcely dissociated the acto-heavy meromyosin complex during the ATPase reaction. These results suggest that Ruthenium red interacts directly with the binding site for F-actin on the myosin heavy chain. This site is considered to be necessary not for maintaining the binding affinity of myosin for F-actin, but for activation of the Mg(2+)-ATPase.
mesh_terms: D000199:Actins / Q000378:metabolism / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001667:Binding, Competitive; D017301:Ca(2+) Mg(2+)-ATPase / Q000187:drug effects*; D002645:Chickens; D004305:Dose-Response Relationship, Drug; D005895:Gizzard, Avian / Q000201:enzymology; D009130:Muscle, Smooth / Q000201:enzymology*; D015879:Myosin Subfragments / Q000187:drug effects / Q000378:metabolism; D009218:Myosins / Q000187:drug effects* / Q000378:metabolism; D012430:Ruthenium Red / Q000494:pharmacology*; D014335:Tropomyosin / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D000199:Actins; D015879:Myosin Subfragments; D014335:Tropomyosin; D012430:Ruthenium Red; D000255:Adenosine Triphosphate; D017301:Ca(2+) Mg(2+)-ATPase; D009218:Myosins