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在平滑肌收缩活动中 ,肌球蛋白轻链激酶 (MLCK)对肌球蛋白轻链 (MLC2 0 )的钙依赖性磷酸化是引起平滑肌收缩的主要原因 ,同时还存在着其它非钙依赖性的调节途径。高浓度的MLCK和Ca2 + independentLC2 0kinase均可引起MLC2 0 的非钙依赖性磷酸化 ;Rho kinase、花生四烯酸及蛋白激酶C等都能抑制肌球蛋白轻链磷酸酶的活性 ,减少MLC2 0 的脱磷酸化 ;调宁蛋白、原肌球蛋白和钙介导蛋白等能通过与肌动蛋白或肌球蛋白的结合来调节肌球蛋白Mg2 + ATP酶活性。这些因素都有助于维持低Ca2 + 时平滑肌的张力。
Calcium-dependent phosphorylation of myosin light chain (MLC20) by myosin light chain kinase (MLCK) is the major cause of smooth muscle contraction during smooth muscle contractile activity, along with other non-calcium-dependent regulation way. High concentration of MLCK and Ca2 + independentLC2 0kinase can cause calcium-independent MLC2 0 phosphorylation; Rho kinase, arachidonic acid and protein kinase C, etc. can inhibit myosin light chain phosphatase activity, reduce MLC20 De novo phosphorylation; tonoplastin, tropomyosin and calcium-mediated protein, etc. through the actin or myosin binding to regulate myosin Mg2 ATP activity. These factors all contribute to the maintenance of smooth muscle tone at low Ca2 +.