Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore.
Nat Commun. 2014 Dec 17;5:5790. doi: 10.1038/ncomms6790.
Tail-anchored (TA) proteins are inserted into membranes post-translationally through a C-terminal transmembrane domain (TMD). The PEX19 protein binds peroxisome TA proteins in the cytoplasm and delivers them to the membrane through the PEX3 receptor protein. An amphipathic segment in PEX19 promotes docking on PEX3. However, how this leads to substrate insertion is unknown. Here we reconstitute peroxisome TA protein biogenesis into two sequential steps of substrate TMD engagement and membrane insertion. We identify a series of previously uncharacterized amphipathic segments in PEX19 and identify one whose hydrophobicity is required for membrane insertion, but not TMD chaperone activity or PEX3 binding. A membrane-proximal hydrophobic surface of PEX3 promotes an unconventional form of membrane intercalation, and is also required for TMD insertion. Together, these data support a mechanism in which hydrophobic moieties in the TMD chaperone and its membrane-associated receptor act in a concerted manner to prompt TMD release and membrane insertion.
尾部锚定（TA）蛋白通过 C 端跨膜结构域（TMD）在翻译后被插入膜中。PEX19 蛋白在细胞质中结合过氧化物酶体 TA 蛋白，并通过 PEX3 受体蛋白将其递送至膜。PEX19 中的一个两亲性片段促进与 PEX3 的对接。然而，这如何导致底物插入尚不清楚。在这里，我们将过氧化物酶体 TA 蛋白生物发生重新组装成底物 TMD 结合和膜插入的两个连续步骤。我们鉴定了 PEX19 中的一系列以前未表征的两亲性片段，并鉴定了一个片段的疏水性对于膜插入是必需的，但对于 TMD 伴侣活性或 PEX3 结合不是必需的。PEX3 的膜近端疏水面促进了一种非常规形式的膜插入，对于 TMD 插入也是必需的。这些数据共同支持了一种机制，其中 TMD 伴侣及其膜相关受体中的疏水性部分以协调的方式起作用，促使 TMD 释放和膜插入。
