Sandri G, Sottocasa G, Panfili E, Liut G
Biochim Biophys Acta. 1979 Dec 4;558(2):214-20. doi: 10.1016/0005-2736(79)90061-0.
Rat liver mitochondria may be subfractionated in sediment and supernatant fractions by swelling in the presence of EDTA and oxaloacetate. The sediment is largely depleted of the Ca2+-binding glycoprotein and its Ca2+-transporting activity may be as low as 10--20% of the starting value. Both the rate of Ca2+ uptake and the capacity to maintain a high Ca2+ concentration gradient across the membrane are depressed. Addition of an osmotic supernatant to the assay mixture may partially restore the original Ca2+-transporting ability. The active component in the supernatant is the Ca2+-binding glycoprotein. This is shown by the following facts: (a) the effect is enhanced by the addition of the purified glycoprotein to the supernatant; (b) precipitation of the glycoprotein from the supernatant by affinity chromatography-purified antibodies abolishes the stimulatory effect, and (c) in the presence of 130 microM Mg2+, the glycoprotein alone may restore fully the Ca2+-transporting ability of the particles. The maximal velocity is already reached at 0.1 microgram glycoprotein/mg mitochondrial protein.
在存在乙二胺四乙酸（EDTA）和草酰乙酸的情况下，通过膨胀可将大鼠肝脏线粒体分级分离为沉淀和上清液部分。沉淀中大量缺乏与钙离子结合的糖蛋白，其钙离子转运活性可能低至起始值的10%-20%。钙离子摄取速率和跨膜维持高钙离子浓度梯度的能力均降低。向测定混合物中添加渗透上清液可部分恢复原始的钙离子转运能力。上清液中的活性成分是与钙离子结合的糖蛋白。以下事实表明了这一点：（a）向上清液中添加纯化的糖蛋白可增强效果；（b）通过亲和色谱纯化的抗体使上清液中的糖蛋白沉淀可消除刺激作用；（c）在存在130微摩尔镁离子的情况下，仅糖蛋白即可完全恢复颗粒的钙离子转运能力。在0.1微克糖蛋白/毫克线粒体蛋白时已达到最大速度。
