Inhibition of smooth muscle actin-activated myosin Mg2+-ATPase activity by caldesmon

• Published in: The Journal of biological chemistry Vol. 259; no. 22; pp. 13656 - 13659
• Main Authors: Ngai, P K, Walsh, M P
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 25.11.1984; American Society for Biochemistry and Molecular Biology
• Subjects: Actins - metabolism; Actomyosin - metabolism; Adenosine Triphosphatases - antagonists & inhibitors; Animals; Biological and medical sciences; Ca(2+) Mg(2+)-ATPase; Calcium - metabolism; Calmodulin - metabolism; Calmodulin-Binding Proteins; Cell physiology; Chemical Precipitation; Chickens; Fundamental and applied biological sciences. Psychology; Gizzard, Avian - analysis; Molecular and cellular biology; Muscle contraction; Muscle, Smooth - enzymology; Myosins - metabolism; Phosphoprotein Phosphatases - pharmacology; Protein Kinases - metabolism; Time Factors; Binding protein; Vertebrata; Gizzard; Actins; Contractile protein; Smooth muscle; Activation; Chicken; Inhibition; Aves; Biological activity; Calmodulin
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)89793-9

Caldesmon, a major calmodulin- and actin-binding protein of smooth muscle (Sobue, K., Muramoto, Y., Fujita, M., and Kakiuchi, S. (1981) Proc. Natl. Acad. Sci. U. S. A. 78, 5652-5655), has been obtained in highly purified form from chicken gizzard by a modification of a previously published procedure (Ngai, P. K., Carruthers, C. A., and Walsh, M. P. (1984) Biochem. J. 218, 863-870) and was found to cause a significant inhibition of both superprecipitation and actin-activated myosin Mg2+-ATPase activity in a system reconstituted from the purified contractile and regulatory proteins without influencing the phosphorylation state of myosin. This inhibitory effect was seen both in the presence and absence of tropomyosin. A Ca2+-and calmodulin-dependent kinase which catalyzed phosphorylation of caldesmon was identified in chicken gizzard; this kinase is distinct from myosin light-chain kinase. Caldesmon prepared by calmodulin-Sepharose affinity chromatography was contaminated with caldesmon kinase activity and was unable to inhibit actomyosin ATPase activity or superprecipitation. Phosphatase activity capable of dephosphorylating caldesmon was also identified in smooth muscle. These results indicate that caldesmon can inhibit smooth muscle actomyosin ATPase activity in vitro, and this function may itself be subject to regulation by reversible phosphorylation of caldesmon.