Bonnet Crystel, Espagne Eric, Zickler Denise, Boisnard Stéphanie, Bourdais Anne, Berteaux-Lecellier Véronique
Institut de Génétique et Microbiologie, UMR-CNRS 8621, Bat 400, Université Paris-Sud, 91405 Orsay Cedex, France.
Mol Microbiol. 2006 Oct;62(1):157-69. doi: 10.1111/j.1365-2958.2006.05353.x.
PEX5, PEX7 and PEX2 are involved in the peroxisomal matrix protein import machinery. PEX5 and PEX7 are the receptors for the proteins harbouring, respectively, a PTS1 and a PTS2 peroxisomal targeting sequence and cycle between the cytoplasm and the peroxisome. PEX2 belongs to the RING-finger complex located in the peroxisomal membrane and acts in protein import downstream of PEX5 and PEX7; it is therefore required for the import of both PTS1 and PTS2 proteins. We have shown previously that PEX2 deficiency leads to an impairment of meiotic commitment in the filamentous fungus Podospora anserina. Here we report that both PEX5 and PEX7 receptors are dispensable for this commitment but are needed for normal sexual cycle. Data suggest also a new role of PEX2 and/or the RING-finger complex in addition to their role in PTS1 and PTS2 import. Strikingly, Deltapex5 and Deltapex7 single and double knockout strains analyses indicate that Deltapex7 acts as a partial suppressor of Deltapex5 life cycle deficiencies. Moreover, contrary to pex2 mutants, Deltapex5 and Deltapex7 show mitochondrial morphological abnormalities.
PEX5、PEX7和PEX2参与过氧化物酶体基质蛋白导入机制。PEX5和PEX7分别是带有过氧化物酶体靶向序列1（PTS1）和过氧化物酶体靶向序列2（PTS2）的蛋白质的受体，在细胞质和过氧化物酶体之间循环。PEX2属于位于过氧化物酶体膜上的泛素连接酶复合物，在PEX5和PEX7下游的蛋白质导入过程中起作用；因此，它是PTS1和PTS2蛋白质导入所必需的。我们之前已经表明，PEX2缺陷会导致丝状真菌嗜热栖热放线菌减数分裂进程受损。在此我们报告，PEX5和PEX7受体对于这一进程并非必需，但对于正常的有性生殖周期是必需的。数据还表明，PEX2和/或泛素连接酶复合物除了在PTS1和PTS2导入中的作用外，还有新的作用。引人注目的是，Δpex5和Δpex7单敲除和双敲除菌株分析表明，Δpex7可部分抑制Δpex5生命周期缺陷。此外，与pex2突变体不同，Δpex5和Δpex7表现出线粒体形态异常。
