The Fe(II) permease Fet4p functions as a low affinity copper transporter and supports normal copper trafficking in Saccharomyces cerevisiae
The Fe(II) permease Fet4p functions as a low affinity copper transporter and supports normal copper trafficking in Saccharomyces cerevisiae
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DOI：
10.1042/0264-6021:3510477
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发表时间：
2000-10-15
影响因子：
4.1
通讯作者：
Kosman, DJ
中科院分区：
文献类型：
--
作者：
Hassett, R;Dix, DR;Kosman, DJ
酿酒酵母的质膜含有对Cu（I）和Fe（II）具有高亲和性的渗透酶。还鉴定了一种低亲和力Fe（II）通透酶，命名为Fet 4p。相应的低亲和力铜通透酶尚未表征，尽管缺乏高亲和力铜摄取的酵母细胞确实积累这种金属离子。我们在本研究中证明，Fet 4p可以作为一个低亲和力的铜通透酶。铜是通过Fet 4p（K-1 = 22 μ M）吸收Fe-55的非竞争性抑制剂。对Fet 4p依赖性Cu-67摄取进行动力学表征，K-m和V-max值分别为35 μ M和8 pmol铜/min/10（6）个细胞。含Fet 4的菌株没有表现出可饱和的、低亲和力的铜摄取，表明这种摄取可归因于Fet 4p。在Fe-55/59摄取中表现出降低效率的Fet 4p突变形式在Cu-67摄取中同样受到损害，表明Fet 4p中相似的氨基酸残基有助于两种摄取过程。通过Fet 4p进入细胞的铜的代谢类似于通过高亲和力通透酶Ctr 1 p进入细胞的铜。这通过Fet 3 p的铜激活的Fet 4p依赖性显示，Fet 3 p是支持酵母中高亲和力铁摄取的铜氧化酶。此外，铜转运的Fet 4p下调铜敏感的转录因子，Mac 1 p。无论是由Ctr 1 p还是Fet 4p提供，细胞内铜浓度约为100 μ g/ml。10 μ M导致Mac Ip转录活性降低50%。这些数据表明，新到达的铜在酵母细胞中的初始贩运是独立的铜吸收途径参与，并且该铜可能是有针对性的第一个大概小的“持有”池之前，其在细胞内的分区。
The plasma-membrane of Saccharomyces cerevisiae contains high affinity permeases for Cu(I) and Fe(II). A low affinity Fe(II) permease has also been identified, designated Fet4p, A corresponding low affinity copper permease has not been characterized, although yeast cells that lack high affinity copper uptake do accumulate this metal ion. We demonstrate in the present study that Fet4p can function as a low affinity copper permease. Copper is a non-competitive inhibitor of Fe-55 uptake through Fet4p (K-1 = 22 muM). Fet4p-dependent Cu-67 uptake was kinetically characterized, with K-m and V-max values of 35 muM and 8 pmol of copper/min per 10(6) cells respectively. A fet4-containing strain exhibited no saturable, low affinity copper uptake indicating that this uptake was attributable to Fet4p. Mutant forms of Fet4p that exhibited decreased efficiency in Fe-55/59 uptake were similarly compromised in Cu-67 uptake, indicating that similar amino acid residues in Fet4p contribute to both uptake processes. The copper taken into the cell by Fet4p was metabolized similarly to the copper taken into the cell by the high affinity permease, Ctr1p. This was shown by the Fet4p-dependence of copper activation of Fet3p, the copper oxidase that supports high affinity iron uptake in yeast. Also, copper-transported by Fet4p down-regulated the copper sensitive transcription factor, Mac1p. Whether supplied by Ctr1p or by Fet4p, an intracellular copper concentration of approx. 10 muM caused a 50 % reduction in the transcriptional activity of Mac Ip. The data suggest that the initial trafficking of newly arrived copper in the yeast cell is independent of the copper uptake pathway involved, and that this copper may be targeted first to a presumably small 'holding' pool prior to its partitioning within the cell.