期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1977
卷号：74
期号：1
页码：129-133
DOI：10.1073/pnas.74.1.129
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：A 35--70% ammonium sulfate fraction of smooth muscle actomyosin was prepared from guinea pig vas deferens. This fraction also contains a smooth muscle myosin kinase and a phosphatase that phosphorylates and dephosphorylates, respectively, the 20,000-dalton light chain of smooth muscle myosin. Phosphorylated and dephosphorylated smooth muscle myosin. Phosphorylated and dephosphorylated smooth muscle myosin were purified from this ammonium sulfate fraction by gel filtration, which also separated the kinase and the phosphatase from the myosin. Purified phosphorylated and dephosphorylated myosin have identical stained patterns after sodium dodecyl sulfate/polyacrylamide gel electrophoresis. They also have similar ATPase activities measured in 0.5 M KCl in the presence of K+-EDTA and Ca2+. However, the actin-activated myosin ATPase activity is markedly increased after phosphorylation. Moreover, the actin-activated ATPase activity of phosphorylated myosin is inhibited by the removal of Ca2+ in the absence of any added regulatory proteins. Dephosphorylation of myosin results in a decrease in the actin-activated ATPase activity. Skeletal muscle tropomyosin markedly increased the actin-activated ATPase activity of phosphorylated but not dephosphorylated myosin in the presence, but not in the absence, of Ca2+.
