Zhao H, Eide D
Department of Biochemistry and Molecular Biology, School of Medicine, University of Minnesota, Duluth, Minnesota 55812, USA.
J Biol Chem. 1996 Sep 20;271(38):23203-10. doi: 10.1074/jbc.271.38.23203.
Zinc accumulation in Saccharomyces cerevisiae occurs through either of two uptake systems. A high affinity system is active in zinc-limited cells, and the ZRT1 gene encodes the transporter protein of this system. In this study, we characterized the low affinity system that is active in zinc-replete cells. The low affinity system is time-, temperature-, and concentration-dependent and prefers zinc over other metals as its substrate. Our results suggest that the ZRT2 gene encodes the transporter of this system. The amino acid sequence of Zrt2p is remarkably similar to those of Zrt1p and Irt1p, an Fe2+ transporter from Arabidopsis thaliana. Overexpressing ZRT2 increased low affinity uptake, whereas disrupting this gene eliminated that activity, but had little effect on the high affinity system. Therefore, the high and low affinity systems are separate uptake pathways. Analysis of the zinc levels required for growth of zrt2 mutant strains as well as the effects of the zrt2 mutation on the regulation of the high affinity system demonstrated that the low affinity system is a biologically relevant mechanism of zinc accumulation. Finally, a zrt1zrt2 mutant was viable, indicating the existence of additional zinc uptake pathways.
酿酒酵母中的锌积累通过两种摄取系统中的任何一种发生。高亲和力系统在锌限制的细胞中起作用，ZRT1基因编码该系统的转运蛋白。在本研究中，我们对在锌充足的细胞中起作用的低亲和力系统进行了表征。低亲和力系统具有时间、温度和浓度依赖性，并且相对于其他金属更喜欢锌作为其底物。我们的结果表明，ZRT2基因编码该系统的转运蛋白。Zrt2p的氨基酸序列与Zrt1p和Irt1p（一种来自拟南芥的Fe2+转运蛋白）的氨基酸序列非常相似。过表达ZRT2增加了低亲和力摄取，而破坏该基因消除了该活性，但对高亲和力系统影响很小。因此，高亲和力和低亲和力系统是独立的摄取途径。对zrt2突变菌株生长所需的锌水平以及zrt2突变对高亲和力系统调节的影响的分析表明，低亲和力系统是锌积累的一种生物学相关机制。最后，zrt1zrt2突变体是有活力的，表明存在其他锌摄取途径。
