Molecular mechanisms for recognition and transport of proteins by a protein complex exists in peroxisomal membrane

通过识别称为 PTS1 和 PTS2 的两种蛋白质靶向信号之一，过氧化物酶体蛋白质从细胞质转运到过氧化物酶体中。去年，我们鉴定了两种可以捕获PTS 1和PTS2的受体（Pex5p和Pex7p），并显示了Pex5p和Pex7p以及Pex5p和过氧化物酶体膜蛋白Pex14p之间的蛋白质-蛋白质相互作用。在本财年，我们生产了通过RNA干扰技术抑制PEX5和PEX7基因表达的转基因植物。对这些转基因植物的分析表明以下两点。 (1) Pex5p 的缺失会抑制含有 PTS1 和 PTS2 的蛋白质进入过氧化物酶体。没有Pex5p的转基因植物显示出乙醛酸体和叶过氧化物酶体的功能缺陷。 (2) Pex7p 的丢失仅抑制含有 PTS2 的蛋白质的输入。不含Pex7p的转基因植物仅表现出乙醛酸酶体功能缺陷。从这些观察中，我们得出结论，Pex5p 和 Pex7p 在胞质溶胶中形成受体-货物复合物，并且受体-货物复合物被 Pex5p 和过氧化物酶体膜蛋白 Pex14p 之间的蛋白质-蛋白质相互作用捕获。

Peroxisomal proteins are transported from the cytosol into peroxisomes by a recognition of one of the two protein targeting signals called PTS1 and PTS2. Last year, we identified two receptors (Pex5p and Pex7p) that can capture PTS 1 and PTS2, and showed protein-protein interaction between Pex5p and Pex7p, as well as Pex5p and a peroxisomal membrane protein, Pex14p. In this fiscal year, we produced transgenic plants that suppressed PEX5-and PEX7-gene expression by RNA interference technology. Analyses of these transgenic plants showed following 2 points. (1) Loss of Pex5p inhibits the import of both PTS1-and PTS2-containing proteins into peroxisomes. The transgenic plants without Pex5p showed defects in functions of both glyoxysomes and leaf peroxisomes. (2) Loss of Pex7p inhibits the import of only PTS2-containing proteins. The transgenic plants without Pex7p showed defect only in glyoxysomal function. From these observation, we concluded that Pex5p and Pex7p form a receptor-cargo complex in the cytosol, and the receptor-cargo complex is captured by the protein-protein interaction between Pex5p and the peroxisomal membrane protein, Pex14p.