Biochemistry Center (BZH), Heidelberg University, D-69120 Heidelberg, Germany.
Institute for Cellular Biochemistry, University Medical Center Göttingen, D-37073 Göttingen, Germany.
Biol Chem. 2022 Aug 18;404(2-3):169-178. doi: 10.1515/hsz-2022-0170. Print 2023 Feb 23.
Peroxisomal matrix proteins are synthesized on cytosolic ribosomes and imported in a posttranslational manner. Intricate protein import machineries have evolved that catalyze the different stages of translocation. In humans, PEX5L was found to be an essential component of the peroxisomal translocon. PEX5L is the main receptor for substrate proteins carrying a peroxisomal targeting signal (PTS). Substrates are bound by soluble PEX5L in the cytosol after which the cargo-receptor complex is recruited to peroxisomal membranes. Here, PEX5L interacts with the docking protein PEX14 and becomes part of an integral membrane protein complex that facilitates substrate translocation into the peroxisomal lumen in a still unknown process. In this study, we show that PEX5L containing complexes purified from human peroxisomal membranes constitute water-filled pores when reconstituted into planar-lipid membranes. Channel characteristics were highly dynamic in terms of conductance states, selectivity and voltage- and substrate-sensitivity. Our results show that a PEX5L associated pore exists in human peroxisomes, which can be activated by receptor-cargo complexes.
过氧化物酶体基质蛋白在细胞质核糖体上合成，并以翻译后方式进行导入。已经进化出复杂的蛋白质导入机制，催化易位的不同阶段。在人类中，PEX5L 被发现是过氧化物酶体转位器的必需组成部分。PEX5L 是携带过氧化物酶体靶向信号 (PTS) 的基质蛋白的主要受体。基质在细胞质中与可溶性 PEX5L 结合，然后货物受体复合物被招募到过氧化物酶体膜上。在这里，PEX5L 与对接蛋白 PEX14 相互作用，并成为促进基质在未知过程中转位到过氧化物酶体腔中的完整膜蛋白复合物的一部分。在这项研究中，我们表明从人过氧化物酶体膜中纯化的包含 PEX5L 的复合物在再构成平面脂质膜时构成充满水的孔。通道特性在电导状态、选择性以及电压和底物敏感性方面具有高度动态性。我们的结果表明，人过氧化物酶体中存在与 PEX5L 相关的孔，该孔可以被受体-货物复合物激活。
