Marston Steve, El-Mezgueldi M
National Heart and Lung Institute, Imperial College London, Dovehouse St., London SW3 6LY, UK.
Adv Exp Med Biol. 2008;644:110-23. doi: 10.1007/978-0-387-85766-4_9.
Smooth muscle contraction is due to the interaction ofmyosin filaments with thin filaments. Thin filaments are composed of actin, tropomyosin, caldesmon and calmodulin in ratios 14:2:1:1. Tissue specific isoforms of act and beta tropomyosin are expressed in smooth muscle. Compared with skeletal muscle tropomyosin, the cooperative activation of actomyosin is enhanced by smooth muscle tropomyosin: cooperative unit size is 10 and the equilibrium between on and off states is shifted towards the on state. The smooth muscle-specific actin-bindingprotein caldesmon, together with calmodulin regulates the activity of the thin filament in response to Ca2+. Caldesmon and calmodulin control the tropomyosin-mediated transition between on and offactivity states.
平滑肌收缩是由于肌球蛋白丝与细肌丝相互作用所致。细肌丝由肌动蛋白、原肌球蛋白、钙调蛋白和钙调素按14:2:1:1的比例组成。平滑肌中表达肌动蛋白和β-原肌球蛋白的组织特异性同工型。与骨骼肌原肌球蛋白相比，平滑肌原肌球蛋白增强了肌动球蛋白的协同激活：协同单位大小为10，开启和关闭状态之间的平衡向开启状态偏移。平滑肌特异性肌动蛋白结合蛋白钙调蛋白与钙调素一起响应Ca2+调节细肌丝的活性。钙调蛋白和钙调素控制原肌球蛋白介导的开启和关闭活性状态之间的转变。
