Fransen Marc, Vastiau Ilse, Brees Chantal, Brys Vanessa, Mannaerts Guy P, Van Veldhoven Paul P
Departement Moleculaire Celbiologie, Afdeling Farmacologie, Katholieke Universiteit Leuven, Faculteit Geneeskunde, Campus Gasthuisberg (O/N 6, box 601), Herestraat 49, 3000 Leuven, Belgium.
J Mol Biol. 2005 Mar 11;346(5):1275-86. doi: 10.1016/j.jmb.2005.01.013. Epub 2005 Jan 28.
Pex19p, a primarily cytosolic protein, is essential for the biogenesis of numerous peroxisomal membrane proteins (PMPs); however, its precise function is unclear. Pex19p might function as a PMP-specific chaperone, a cycling PMP-receptor protein, a PMP membrane insertion factor, or an association/dissociation factor of membrane-associated protein complexes. Alternatively, Pex19p might act as a multifunctional peroxin and participate in a number of these activities. Here, we have employed transposon mutagenesis to generate a library of human pex19 alleles coding for Pex19p variants containing random in-frame pentapeptide insertions. A total of 87 different variants were characterized to identify functionally important regions. These studies revealed that Pex19p has a tripartite domain structure consisting of: (i) an amino-terminal domain that binds to Pex3p and is essential for docking at the peroxisome membrane; (ii) a central domain that competes with Pex5p and Pex13p for binding to Pex14p and may play a role in the assembly of PTS-receptor docking complexes; and (iii) a carboxy-terminal domain that interacts with multiple PMPs including Pex3p, Pex11pbeta, Pex12p, Pex13p, Pex16p, and Pex26p. Whether the latter interactions constitute the chaperone or transport functions (or both), remains to be determined. Finally, our observation that Pex19p contains two distinct binding sites for Pex3p suggests that the peroxin may bind PMPs in multiple places and for multiple purposes.
Pex19p是一种主要存在于胞质中的蛋白质，对众多过氧化物酶体膜蛋白（PMPs）的生物合成至关重要；然而，其确切功能尚不清楚。Pex19p可能作为PMP特异性伴侣蛋白、循环PMP受体蛋白、PMP膜插入因子或膜相关蛋白复合物的缔合/解离因子发挥作用。或者，Pex19p可能作为多功能过氧化物酶体蛋白参与其中一些活动。在这里，我们利用转座子诱变生成了一个人类pex19等位基因文库，这些等位基因编码含有随机框内五肽插入的Pex19p变体。共对87种不同变体进行了表征以确定功能重要区域。这些研究表明，Pex19p具有三重结构域结构，包括：（i）氨基末端结构域，可与Pex3p结合，对停靠在过氧化物酶体膜上至关重要；（ii）中央结构域，与Pex5p和Pex13p竞争与Pex14p结合，可能在PTS受体停靠复合物的组装中发挥作用；（iii）羧基末端结构域，与多种PMP相互作用，包括Pex3p、Pex11pβ、Pex12p、Pex13p、Pex16p和Pex26p。后者的相互作用是否构成伴侣蛋白或转运功能（或两者兼有），仍有待确定。最后，我们观察到Pex19p含有两个不同的Pex3p结合位点，这表明该过氧化物酶体蛋白可能在多个位置以多种目的结合PMPs。
