METAL BINDING TO PLANT METALLOTHIONEINS

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 植物金属硫蛋白(MTS)是一类普遍存在的蛋白质，在金属离子动态平衡、解毒和植物发育中的作用尚不清楚。植物MT是一种低分子、富含半胱氨酸的蛋白质，具有极高的金属离子含量(高达7个质量当量)。与它们的哺乳动物同行相比，关于植物MTS的现有信息相当有限，这一领域的研究活动直到最近才开始增加[例如1]。我们的团队也是在今年才确定了植物MT的第一个三维结构，特别是种子特异的小麦Zn6Ec-1蛋白的较大结构域。虽然我们现在已经有了来自四个不同植物MT亚群的一些MT的每个蛋白质的金属离子数量的简明数据，但配位配体的性质并不总是清楚的。虽然金属离子主要结合在四面体四硫酸盐配位环境中，但偶尔也发现高度保守的His残基，这也可能起到一定的作用。我们也有越来越多的证据表明，存在更多亲和力较低的金属离子结合位点。在这种新的配位模式中，Cys残基只起到很小的作用是非常可行的。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Plant metallothioneins (MTs) are a ubiquitous class of proteins with a specific but mostly still unknown role in metal ion homeostasis, detoxification, and plant development. Plant MTs are low molecular mass, cysteine-rich proteins with an extremely high metal ion content (up to 7 mass equivalents). In contrast to their mammalian counterparts, the information available about plant MTs are rather limited and research activities in this area only started to increase recently [e.g. 1]. It was also only this year that our group determined the first three dimensional structure of a plant MT, specifically of the larger domain of the seed-specific wheat Zn6Ec-1 protein. While we have now concise data about the number of metal ions per protein at hand for a number of MTs from the four different plant MT subgroups, the nature of the coordinating ligands is not always clear. While metal ions are predominantly bound in tetrahedral tetrathiolate coordination environments, occasionally highly conserved His residues are found, which might play a role as well. We also have increasing evidence for the existence of additional metal ion binding sites with lower affinity. It is very well feasible that Cys residues have only a minor role in this new coordination mode.