Transport of metal ions-Structural and functional analysis of a novel metal transporter

本研究以人工底物叶绿酸镁代替真底物叶绿酸镁进行镁脱螯合反应。在这项研究中，除了镁脱螯合物质（MCS）的参与镁脱螯合蛋白被发现。在这里，我们报告这项研究的结果。结果表明，至少存在三种具有镁释放能力的同工酶。我们将这些蛋白命名为Mg释放蛋白（MRP），并对这些蛋白进行了纯化和鉴定。两种蛋白质的分子量分别为20 k和43 k。酶反应强烈抑制自由基清除剂，类似辣根过氧化物酶。然而，MRP的吸收光谱与辣根过氧化物酶的吸收光谱有很大不同。镁释放蛋白没有活性叶绿素a，一个真正的基板。这可能是推断MRPs参与Mg的释放和/或运输，但它们不同于Mg-脱螯合酶，其参与叶绿素降解途径中的Mg的释放。目前，我们正在研究具有43 k和另一种同工酶的MRP和MRP基因的克隆。

In this study, we investigated on Mg-dechelation reaction using artificial substrate, Mg-chlorophyllin, instead of true substrate, chlorophyllide a. During this study, an involvement of Mg-dechelating proteins in addition to the Mg-dechelating substance (MCS) was found. Here, we report the results of this study. The results revealed the presence of at least three isozymes which have Mg-releasing ability. We designated these proteins as Mg-releasing protein (MRP) and purification and characterization of these proteins were carried. Molecular weight of two proteins was estimated to be 20 k and 43 k. The enzyme reaction was strongly inhibited by free radical scavengers as similar to horseradish peroxidase. Absorption spectrum of MRP was, however, very different from that of horseradish peroxidase. The Mg-releasing protein had no activity for chlorophyllide a, a true substrate. It is likely to conclude that MRPs involve Mg-releasing and /or transport, but they are different from Mg-dechelatase that participates releasing of Mg in the chlorophyll degradation pathway. We are now studying on the MRP having 43 k and one another isozymes and cloning of MRP gene.