Ca2+- and calmodulin-dependent stimulation of smooth muscle actomyosin Mg2+-ATPase by fodrin

• Published in: Biochemistry (Easton) Vol. 26; no. 4; pp. 1110 - 1117
• Main Authors: CHIAYENG WANG, NGAI, P. K, WALSH, M. P, WANG, J. H
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 24.02.1987
• Subjects: Actins - metabolism; Actomyosin - metabolism; Animals; Biological and medical sciences; Brain - metabolism; Ca(2+) Mg(2+)-ATPase - metabolism; Calcium - pharmacology; Calmodulin - pharmacology; Carrier Proteins - isolation & purification; Carrier Proteins - pharmacology; Cattle; Cell physiology; Chickens; Fundamental and applied biological sciences. Psychology; Gizzard, Avian - enzymology; Kinetics; Microfilament Proteins - isolation & purification; Microfilament Proteins - pharmacology; Molecular and cellular biology; Muscle contraction; Muscle, Smooth - enzymology; Myosins - metabolism; Nerve Tissue Proteins - isolation & purification; Nerve Tissue Proteins - pharmacology; Rabbits; Brain; Actomyosin; Gizzard; Contractile protein; Ox; Molecular interaction; Smooth muscle; Activation; Calcium Ions; Muscle contraction; Vertebrata; Regulation(control); Mammalia; Artiodactyla; Ungulata; Calmodulin
• ISSN: 0006-2960; 1520-4995

Fodrin, a spectrin-like actin and calmodulin binding protein, was purified to electrophoretic homogeneity from a membrane fraction of bovine brain. The effect of fodrin on smooth muscle actomyosin Mg2+-ATPase activity was examined by using a system reconstituted from skeletal muscle actin and smooth muscle myosin and regulatory proteins. The simulation of actomyosin Mg2+-ATPase by fodrin showed a biphasic dependence on fodrin concentration and on the time of actin and myosin preincubation at 30 degrees C. Maximal stimulation (50-70%) was obtained at 3 nM fodrin following 10 min of preincubation of actin and myosin. This stimulation was also dependent on the presence of tropomyosin. In the absence of myosin light chain kinase, the fodrin stimulation of Mg2+-ATPase could not be demonstrated with normal actomyosin but could be demonstrated with acto-thiophosphorylated myosin, suggesting that fodrin stimulation depends on the phosphorylation of myosin. Fodrin stimulation was shown to require the presence of both Ca2+ and calmodulin when acto-thiophosphorylated myosin was used. These observations suggest a possible functional role of fodrin in the regulation of smooth muscle contraction and demonstrate an effect on Ca2+ and calmodulin on fodrin function.