Functional comparisons between isoforms of the sarcoplasmic or endoplasmic reticulum family of calcium pumps.
Functional comparisons between isoforms of the sarcoplasmic or endoplasmic reticulum family of calcium pumps.
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DOI：
10.1016/s0021-9258(19)49738-x
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发表时间：
1992-07
期刊：
影响因子：
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通讯作者：
J. Lytton;M. Westlin;S. E. Burk;G. Shull;D. Maclennan
中科院分区：
文献类型：
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作者：
J. Lytton;M. Westlin;S. E. Burk;G. Shull;D. Maclennan
存在于细胞内细胞器中的ATP依赖性钙泵由结构相关的酶家族编码，称为肌质或内质网Ca（2+）-ATP酶（SERCA），其各自具有不同的组织特异性和发育调节表达模式。COS-1细胞表达系统用于检查亚型的生化特性：SERCA 1（快速收缩骨骼肌）。SERCA 2a（心脏/慢收缩骨骼肌）、SERCA 2b（普遍存在的平滑肌和非肌肉）和SERCA 3（非肌肉）。每种异构体都有效表达，并且似乎靶向内质网。所有异构体显示定性相似的酶性质，并激活钙在合作的方式与希尔系数为2。SERCA 1和SERCA 2a（肌肉亚型）的定量特性在所有方面都是相同的。然而，SERCA 2b似乎具有较低的钙转运和ATP水解的周转率。SERCA 3表现出降低的表观亲和力的钙，增加的表观亲和力的钒酸盐，和改变pH值的依赖性相比，与其他亚型。这些性质与E1和E2构象之间的平衡向E2状态移动的酶一致。
ATP-dependent calcium pumps that reside in intracellular organelles are encoded by a family of structurally related enzymes, termed the sarcoplasmic or endoplasmic reticulum Ca(2+)-ATPases (SERCA), which each have a distinct pattern of tissue-specific and developmentally regulated expression. A COS-1 cell expression system was used to examine the biochemical properties of the isoforms: SERCA1 (fast-twitch skeletal muscle). SERCA2a (cardiac/slow-twitch skeletal muscle), SERCA2b (ubiquitous smooth- and non-muscle), and SERCA3 (non-muscle). Each isoform was expressed efficiently and appeared to be targeted to the endoplasmic reticulum. All isoforms displayed qualitatively similar enzymatic properties and were activated by calcium in a cooperative manner with a Hill coefficient of 2. The quantitative properties of SERCA1 and SERCA2a (the muscle isoforms) were identical in all respects. SERCA2b, however, appeared to have a lower turnover rate for both calcium transport and ATP hydrolysis. SERCA3 displayed a reduced apparent affinity for calcium, an increased apparent affinity for vanadate, and an altered pH dependence when compared with the other isoforms. These properties are consistent with an enzyme in which the equilibrium between the E1 and E2 conformations is shifted toward the E2 state.