Panfili E, Sottocasa G L, Sandri G, Liut G
Eur J Biochem. 1980 Mar;105(1):205-10. doi: 10.1111/j.1432-1033.1980.tb04490.x.
A change in the redox state of pyridine nucleotides such as that evoked by addition of oxaloacetate has been shown to promote Ca2+ efflux from Ca2+ pre-loaded respiring mitochondria. An affinity-chromatography-purified antibody preparation obtained against the mitochondrial Ca2+-binding glycoprotein inhibits the phenomenon. This finding suggests that the glycoprotein is involved also in the oxaloacetate-induced Ca2+ release. This conclusion is reinforced by the finding that Ca2+-binding glycoprotein shows four sites per molecule where the pyridine nucleotides may be bound. Binding of NAD+ occurs preferentially over the others and the binding shows positive cooperativity, indicating that the glycoprotein undergoes an allosteric change upon NAD+ binding. Interestingly, in addition, NAD+ lowers the affinity of the glycoprotein for Ca2+. The effect cannot be induced by NADH. Pyridine nucleotide phosphates, NADP+ and NADPH, are essentially not bound. The results are consistent with the view that the glycoprotein is the site of regulation of Ca2+ equilibration across the mitochondrial membrane and make it possible to conclude that the effector in the phenomenon is NAD+.
诸如添加草酰乙酸所引发的吡啶核苷酸氧化还原状态的变化，已被证明可促进Ca2+从预先加载了Ca2+的呼吸性线粒体中流出。一种通过亲和层析纯化得到的、针对线粒体Ca2+结合糖蛋白的抗体制剂可抑制这一现象。这一发现表明该糖蛋白也参与了草酰乙酸诱导的Ca2+释放。Ca2+结合糖蛋白每个分子显示有四个可结合吡啶核苷酸的位点，这一发现进一步支持了这一结论。NAD+的结合优先于其他物质，且这种结合显示出正协同性，表明该糖蛋白在结合NAD+后会发生别构变化。有趣的是，此外，NAD+会降低该糖蛋白对Ca2+的亲和力。NADH不能诱导这种效应。吡啶核苷酸磷酸，即NADP+和NADPH，基本上不被结合。这些结果与以下观点一致，即该糖蛋白是跨线粒体膜Ca2+平衡调节的位点，并且可以得出结论，该现象中的效应物是NAD+。
