Nishio H, Ichikawa K, Hartshorne D J
Muscle Biology Group, University of Arizona, Tucson 85721, USA.
Biochem Biophys Res Commun. 1997 Jul 30;236(3):570-5. doi: 10.1006/bbrc.1997.7005.
Protein phosphatase was partially purified from myofibrils of bovine heart by sequential column chromatographies. The purified protein phosphatase was immunologically identified as a delta isoform of PP1 (PP1delta). The myosin-binding subunit (MBS) of myosin-binding phosphatase (MBP) in smooth muscle was co-purified with PP1delta at each step of the sequential column chromatographies. The immunoprecipitation experiment using the polyclonal antibody to MBS showed that PP1delta associates with MBS in the purified phosphatase. In addition, the myosin-binding assay showed that the purified phosphatase has the characteristics of binding to cardiac myosin. These data strongly suggest that MBP, the holoenzyme composed of PP1delta and MBS, is expressed in heart myofibrils.
通过连续柱层析从牛心脏肌原纤维中部分纯化了蛋白磷酸酶。纯化的蛋白磷酸酶经免疫鉴定为PP1的δ亚型（PP1δ）。在连续柱层析的每个步骤中，平滑肌中的肌球蛋白结合磷酸酶（MBP）的肌球蛋白结合亚基（MBS）都与PP1δ共纯化。使用针对MBS的多克隆抗体进行的免疫沉淀实验表明，PP1δ在纯化的磷酸酶中与MBS相关联。此外，肌球蛋白结合试验表明，纯化的磷酸酶具有与心肌肌球蛋白结合的特性。这些数据有力地表明，由PP1δ和MBS组成的全酶MBP在心脏肌原纤维中表达。
