Alessi D, MacDougall L K, Sola M M, Ikebe M, Cohen P
Department of Biochemistry, University of Dundee, Scotland.
Eur J Biochem. 1992 Dec 15;210(3):1023-35. doi: 10.1111/j.1432-1033.1992.tb17508.x.
The major protein phosphatase that dephosphorylates smooth-muscle myosin was purified from chicken gizzard myofibrils and shown to be composed of three subunits with apparent molecular masses of 130, 37 and 20 kDa, the most likely structure being a heterotrimer. The 37-kDa component was the catalytic subunit, while the 130-kDa and 20-kDa components formed a regulatory complex that enhanced catalytic subunit activity towards heavy meromyosin or the isolated myosin P light chain from smooth muscle and suppressed its activity towards phosphorylase, phosphorylase kinase and glycogen synthase. The catalytic subunit was identified as the beta isoform of protein phosphatase-1 (PP1) and the 130-kDa subunit as the PP1-binding component. The distinctive properties of smooth and skeletal muscle myosin phosphatases are explained by interaction of PP1 beta with different proteins and (in conjunction with earlier analysis of the glycogen-associated phosphatase) establish that the specificity and subcellular location of PP1 is determined by its interaction with a number of specific targetting subunits.
从鸡砂囊肌原纤维中纯化出了使平滑肌肌球蛋白去磷酸化的主要蛋白磷酸酶，结果表明它由三个亚基组成，其表观分子量分别为130、37和20 kDa，最可能的结构是异源三聚体。37 kDa的成分是催化亚基，而130 kDa和20 kDa的成分形成一个调节复合物，该复合物增强了催化亚基对重酶解肌球蛋白或平滑肌中分离出的肌球蛋白P轻链的活性，并抑制其对磷酸化酶、磷酸化酶激酶和糖原合酶的活性。催化亚基被鉴定为蛋白磷酸酶-1（PP1）的β同工型，130 kDa的亚基为PP1结合成分。平滑肌和骨骼肌肌球蛋白磷酸酶的独特性质可通过PP1β与不同蛋白质的相互作用来解释，并且（结合糖原相关磷酸酶的早期分析）证实PP1的特异性和亚细胞定位是由其与许多特定靶向亚基的相互作用决定的。
