Eci1p uses a PTS1 to enter peroxisomes: either its own or that of a partner, Dci1p.
Eci1p uses a PTS1 to enter peroxisomes: either its own or that of a partner, Dci1p.
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Eci1p 使用 PTS1 进入过氧化物酶体：它自己的或伙伴 Dci1p 的过氧化物酶体。
DOI：
10.1078/0171-9335-00144
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发表时间：
2001
影响因子：
6.6
通讯作者：
Lazarow,PB
中科院分区：
文献类型：
--
作者：
Yang,X;Purdue,PE;Lazarow,PB
酿酒酵母Δ3，Δ2-烯酰辅酶A异构酶（Eci 1 p）由ECI 1编码，是不饱和脂肪酸β-氧化的必需酶。据报道，以及在这项研究中证实，它是一种过氧化物酶体蛋白。与许多其他过氧化物酶体蛋白不同，Eci 1 p在其羧基末端（-HRL）具有过氧化物酶体靶向信号1型（PTS 1）样信号，在其氨基末端（RIEGPFFIIHL）具有PTS 2样信号。我们已经发现，过氧化物酶体靶向由位于绿色荧光蛋白（GFP）前面的Eci 1 p组成的融合蛋白不依赖于Pex 7 p（PTS 2受体），排除了PTS 2机制，但依赖于Pex 5 p（PTS 1受体）。这种Pex 5 p依赖性是出乎意料的，因为推定的Eci 1 p的PTS 1不在融合蛋白的C末端;实际上，从融合物中删除该信号（-HRL-）不影响Pex 5 p依赖性靶向。与此一致，Pex 5 p在双杂交试验中与Eci 1 p和Eci 1 p ΔHRL相互作用。通过用Pex 5 p（N495 K）替换Pex 5 p，消除了Eci 1 p-GFP靶向和Eci 1 p Δ HRL相互作用，Pex 5 p（N495 K）是一种点突变的Pex 5 p，其特异性地消除了PTS 1蛋白输入途径。因此，Eci 1 p过氧化物酶体靶向确实需要Pex 5 p依赖性PTS 1途径，但不需要其自身的PTS 1。通过破坏ECI 1和DCI 1，我们发现Dci 1 p，一种与Eci 1 p具有50%同一性的过氧化物酶体PTS 1蛋白，是Eci 1 p-GFP靶向所必需的。这表明Eci 1 p-GFP的Pex 5 p依赖性输入是由于与Dci 1 p的相互作用和共输入。尽管C-末端HRL在野生型细胞中的输入是可分配的，但我们还表明，这种三肽可以作为PTS 1发挥作用，尽管相当弱，并且对于在不存在Dci 1 p的情况下靶向是必需的。因此，Eci 1 p可以通过其自身的PTS 1或作为与Dci 1 p的异源寡聚体靶向过氧化物酶体。这些数据证明了Eci 1 p的一种新的冗余靶向途径。
Saccharomyces cerevisiae Δ3,Δ2-enoyl-CoA isomerase (Eci1p), encoded by ECI1, is an essential enzyme for the β-oxidation of unsaturated fatty acids. It has been reported, as well as confirmed in this study, to be a peroxisomal protein. Unlike many other peroxisomal proteins, Eci1p possesses both a peroxisome targeting signal type 1 (PTS1)-like signal at its carboxy-terminus (-HRL) and a PTS2-like signal at its amino-terminus (RIEGPFFIIHL). We have found that peroxisomal targeting of a fusion protein consisting of Eci1p in front of green fluorescent protein (GFP) is not dependent on Pex7p (the PTS2 receptor), ruling out a PTS2 mechanism, but is dependent on Pex5p (the PTS1 receptor). This Pex5p – dependence was unexpected, since the putative PTS1 of Eci1p is not at the C-terminus of the fusion protein; indeed, deletion of this signal (-HRL-) from the fusion did not affect the Pex5p – dependent targeting. Consistent with this, Pex5p interacted in two-hybrid assays with both Eci1p and Eci1pΔHRL. Eci1p-GFP targeting and Eci1pΔHRLinteraction were abolished by replacement of Pex5p with Pex5p(N495K), a point-mutated Pex5p that specifically abolishes the PTS1 protein import pathway. Thus, Eci1p peroxisomal targeting does require the Pex5p – dependent PTS1 pathway, but does not require a PTS1 of its own. By disruption of ECI1 and DCI1, we found that Dci1p, a peroxisomal PTS1 protein that shares 50% identity with Eci1p, is necessary for Eci1p-GFP targeting. This suggests that the Pex5p – dependent import of Eci1p-GFP is due to interaction and co-import with Dci1p. Despite the dispensability of the C-terminal HRL for import in wild-type cells, we have also shown that this tripeptide can function as a PTS1, albeit rather weakly, and is essential for targeting in the absence of Dci1p. Thus, Eci1p can be targeted to peroxisomes by its own PTS1 or as a hetero-oligomer with Dci1p. These data demonstrate a novel, redundant targeting pathway for Eci1p.