Portnoy M E, Schmidt P J, Rogers R S, Culotta V C
Department of Biochemistry, Johns Hopkins University School of Public Health, Baltimore, MD 21205, USA.
Mol Genet Genomics. 2001 Jul;265(5):873-82. doi: 10.1007/s004380100482.
Copper metallochaperones represent a new family of soluble, low-molecular-weight proteins that function to deliver copper to specific sites within a cell. How the metallochaperones acquire their copper, however, is not known. In this study, we have conducted a survey of known metal ion transporters in bakers' yeast, Saccharomyces cerevisiae, to identify those that contribute copper to pathways involving the metallochaperones Atxlp and Lys7p. The results indicatethat, in addition to the well known Ctr1p and Ctr3p high-affinity copper transporters, the metallochaperones can acquire their copper through pathways involving the relatively non-specific divalent metal ion transporter Fet4p and the putative low-affinitycopper transporter Ctr2p. We have examined the localization of Ctr2p using an epitope tagged version of the protein and find that Ctr2p does not localize to the cell surface but may operate at the level of the vacuole to mobilize intracellular copper. Inaddition to Ctrlp, Ctr2p, Ctr3p and Fet4p, other metal transport systems can act as upstream donors of copper for the metallochaperones when copper availability in the medium is increased. Although the nature of these auxiliary systems is unknown, they do not appear to involve the yeast members of the Nramp family of divalent transporters, or uptake mechanisms that involve endocytosis. Since vastly different metal transporters located at either the cell surface or intracellular sites can all contribute copper to metallochaperones, it is unlikely that the metallochaperones directly interact with the metal transporters to obtain the metal.
铜金属伴侣蛋白代表了一类新的可溶性低分子量蛋白质家族，其功能是将铜输送到细胞内的特定部位。然而，金属伴侣蛋白如何获取铜尚不清楚。在本研究中，我们对面包酵母酿酒酵母中已知的金属离子转运蛋白进行了调查，以确定那些为涉及金属伴侣蛋白Atxlp和Lys7p的途径提供铜的转运蛋白。结果表明，除了众所周知的高亲和力铜转运蛋白Ctr1p和Ctr3p外，金属伴侣蛋白还可以通过涉及相对非特异性的二价金属离子转运蛋白Fet4p和假定的低亲和力铜转运蛋白Ctr2p的途径获取铜。我们使用该蛋白的表位标签版本检查了Ctr2p的定位，发现Ctr2p并不定位于细胞表面，而是可能在液泡水平发挥作用以动员细胞内的铜。除了Ctrlp、Ctr2p、Ctr3p和Fet4p外，当培养基中的铜可用性增加时，其他金属转运系统也可以作为金属伴侣蛋白的上游铜供体。尽管这些辅助系统的性质尚不清楚，但它们似乎不涉及二价转运蛋白Nramp家族的酵母成员，也不涉及涉及内吞作用的摄取机制。由于位于细胞表面或细胞内位点的截然不同的金属转运蛋白都可以为金属伴侣蛋白提供铜，因此金属伴侣蛋白不太可能直接与金属转运蛋白相互作用以获取金属。
