Trotter J A, Adelstein R S
J Biol Chem. 1979 Sep 25;254(18):8781-5.
Myosin was purified from rabbit alveolar macrophages in a form that could not be activated by actin. This myosin could be phosphorylated by an endogenous myosin light chain kinase, up to 2 mol of phosphate being incorporated/mol of myosin. The site phosphorylated was located on the 20,000-dalton myosin light chain. Phosphorylation of macrophage myosin was found to be necessary for actin activation of myosin ATPase activity. Moreover, the actin-activated ATPase activity was found to vary directly with the extent of myosin phosphorylation, maximal phosphorylation (2 mol of Pi/mol of myosin) resulting in an actin-activated MgATPase activity of approximately 200 nmol of Pi/mg of myosin/min at 37 degrees C. These results establish that phosphyoyration of the 20,000-dalton light chain of myosin is sufficient to regulate the actin-activated ATPase activity of macrophage myosin.
肌球蛋白是从兔肺泡巨噬细胞中纯化得到的，其形式无法被肌动蛋白激活。这种肌球蛋白可被内源性肌球蛋白轻链激酶磷酸化，每摩尔肌球蛋白最多可掺入2摩尔磷酸盐。磷酸化位点位于20000道尔顿的肌球蛋白轻链上。研究发现，巨噬细胞肌球蛋白的磷酸化是肌动蛋白激活肌球蛋白ATP酶活性所必需的。此外，还发现肌动蛋白激活的ATP酶活性与肌球蛋白的磷酸化程度直接相关，最大磷酸化（每摩尔肌球蛋白2摩尔无机磷）导致在37℃时肌动蛋白激活的MgATP酶活性约为每毫克肌球蛋白每分钟200纳摩尔无机磷。这些结果表明，肌球蛋白20000道尔顿轻链的磷酸化足以调节巨噬细胞肌球蛋白的肌动蛋白激活ATP酶活性。
