title: Ca(2+)-dependent inhibition of actin-activated myosin ATPase activity by S100C (S100A11), a novel member of the S100 protein family.
abstract: S100C (S100A11, calgizzarin) inhibits the actin-activated myosin Mg(2+)-ATPase activity of smooth muscle in a dose-dependent manner: its half-maximal effect occurs at a S100C/actin molar ratio of 0.05 and its maximal effect occurs at a ratio of 0.20. Furthermore, S100C was found to bind to actin with a stoichiometry of 1:6-7 in the presence of Ca(2+), with an affinity of 1 x 10(-6) M determined by cosedimentation assays. Other Ca(2+)-binding proteins such as S100A1, S100A2, S100B, and calmodulin did not inhibit actin-activated myosin Mg(2+)-ATPase activity. Calmodulin, S100A1, and S100B reversed the inhibitory effect of calponin in a Ca(2+)-dependent manner, S100A2 had no effect, and S100C had additional inhibitory effects. The results suggest that S100C might be involved in the regulation of actin-activated myosin Mg(2+)-ATPase activity through its Ca(2+)-dependent interaction with actin filaments.
authors.affiliation: Department of Molecular Pharmacology, Mie University School of Medicine, Tsu, 514-8507, Japan.
authors.forename: X Q
authors.initials: XQ
authors.lastname: Zhao
authors.forename: M
authors.initials: M
authors.lastname: Naka
authors.forename: M
authors.initials: M
authors.lastname: Muneyuki
authors.forename: T
authors.initials: T
authors.lastname: Tanaka
mesh_terms: D000199:Actins / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000037:antagonists & inhibitors*; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism; D002417:Cattle; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D007700:Kinetics; D018482:Muscle, Skeletal / Q000378:metabolism; D009218:Myosins / Q000037:antagonists & inhibitors*; D011817:Rabbits; D009418:S100 Proteins / Q000302:isolation & purification / Q000378:metabolism*; D013552:Swine
chemical_list: D000199:Actins; D002147:Calmodulin; D004791:Enzyme Inhibitors; D009418:S100 Proteins; C072337:S100A11 protein, human; D000255:Adenosine Triphosphate; D017301:Ca(2+) Mg(2+)-ATPase; D009218:Myosins; D002118:Calcium