Ubiquitination of the peroxisomal import receptor Pex5p
Ubiquitination of the peroxisomal import receptor Pex5p
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DOI：
10.1042/bj20040572
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发表时间：
2004-11-15
影响因子：
4.1
通讯作者：
Erdmann, R
中科院分区：
文献类型：
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作者：
Platta, H;Girzalsky, W;Erdmann, R
含有 I 型过氧化物酶体靶向信号 (PTS1) 的蛋白质被胞质溶胶中的输入受体 Pex5p 识别，引导它们到达过氧化物酶体膜上的对接和易位复合物。我们证明了 Pex5p 在缺乏过氧化物酶体 AAA（与各种细胞活动相关的 ATP 酶）成分或过氧化物酶体蛋白输入机制的 Pex4p-Pex22p 复合物的细胞中以及在蛋白酶体降解影响的细胞中泛素化。在缺乏 Pex4p-Pex22p 复合物成分的细胞中，单泛素化 Pex5p 代表主要修饰，而在缺乏 AAA 复合物成分的细胞中，多泛素化形式最为突出。对接步骤后，Pex5p 的泛素化仅发生在过氧化物酶体膜上，并且需要环指过氧化物蛋白 Pex10p 的存在。单泛素化和多泛素化被证明依赖于泛素结合酶 Ubc4p，这表明 Pex5p 的泛素化形式是蛋白酶体降解的目标。蛋白酶体突变体中泛素化 Pex5p 的积累表明，Pex5p 泛素化也发生在过氧化物酶体生物发生未受影响的菌株中，表明 Pex5p 泛素化代表了 Pex5p 受体循环中的真正阶段。
Proteins harbouring a peroxisomal targeting signal of type I (PTS1) are recognized by the import receptor Pex5p in the cytosol which directs them to a docking and translocation complex at the peroxisomal membrane. We demonstrate the ubiquitination of Pex5p in cells lacking components of the peroxisomal AAA (ATPases associated with various cellular activities) or Pex4p-Pex22p complexes of the peroxisomal protein import machinery and in cells affected in proteasomal degradation. In cells lacking components of the Pex4p-Pex22p complex, mono-ubiquitinated Pex5p represents the major modification, while in cells lacking components of the AAA complex polyubiquitinated forms are most prominent. Ubiquitination of Pex5p is shown to take place exclusively at the peroxisomal membrane after the docking step,and requires the presence of the RING-finger peroxin Pex10p. Mono- and poly-ubiquitination are demonstrated to depend on the ubiquitin-conjugating enzyme Ubc4p, suggesting that the ubiquitinated forms of Pex5p are targeted for proteasomal degradation. Accumulation of ubiquitinated Pex5p in proteasomal mutants demonstrates that the ubiquitination of Pex5p also takes place in strains which are not affected in peroxisomal biogenesis, indicating that the ubiquitination of Pex5p represents a genuine stage in the Pex5p receptor cycle.