The N-terminal cleavable extension of plant carrier proteins is responsible for efficient insertion into the inner mitochondrial membrane.
The N-terminal cleavable extension of plant carrier proteins is responsible for efficient insertion into the inner mitochondrial membrane.
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植物载体蛋白的 N 端可裂解延伸负责有效插入线粒体内膜。
DOI：
10.1016/j.jmb.2005.06.004
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发表时间：
2005
影响因子：
5.6
通讯作者：
J. Whelan
中科院分区：
文献类型：
--
作者：
M. Murcha;A. Millar;J. Whelan
植物线粒体载体蛋白的一个子集包含一个可切割的N-末端延伸。我们使用一个重组的蛋白质导入检测系统进入膜间隙耗尽的线粒体，以研究可切割延伸在载体导入途径中的作用。通过加入从植物线粒体中分离出来的可溶性膜间空隙部分，可以刺激载体蛋白插入内膜。与不包含可切割延伸的氧戊二酸载体(OMT)相比，含有N-末端可切割延伸的腺核苷酸载体(ANT)和磷酸载体(Pic)的进口刺激更大。去除ANT和Pic的N端可切割延伸导致失去插入内膜的刺激。相反，从ANT或Pic延伸到OMT的N-末端延伸显著地增强了对内膜的插入。通过载体输入途径输入的多位内膜蛋白TIM17和TIM23没有可切割的延伸，通过添加膜间间隙部分显示出高水平的插入内膜的刺激。从载体蛋白到TIM23的N末端可切割延伸部分的添加促进了TIM23插入内膜，即使在没有可溶性膜间隙部分的情况下也是如此。综上所述，这些结果表明，植物载体蛋白上的可切割N-末端延伸是有效插入线粒体内膜所必需的，它们可以刺激任何类似载体的蛋白插入内膜。
A subset of mitochondrial carrier proteins from plants contain a cleavable N-terminal extension. We have used a reconstituted protein import assay system into intermembrane space-depleted mitochondria to study the role of the cleavable extension in the carrier import pathway. Insertion of carrier proteins into the inner membrane can be stimulated by the addition of a soluble intermembrane space fraction isolated from plant mitochondria. Greater stimulation of import of the adenine nucleotide carrier (ANT) and phosphate carrier (Pic), which contain N-terminal cleavable extensions, was observed compared to the import of the oxoglutarate malate carrier (OMT), which does not contain a cleavable extension. Removal of the N-terminal cleavable extension from ANT and Pic resulted in loss of stimulation of insertion into the inner membrane. Conversely, addition of the N-terminal extension from ANT or Pic to OMT resulted in significantly enhanced insertion into the inner membrane. The polytopic inner membrane proteins TIM17 and TIM23 that are imported via the carrier import pathway contain no cleavable extension, displayed high-level stimulation of insertion into the inner membrane by addition of the intermembrane space fraction. Addition of the N-terminal cleavable extension from carrier proteins to TIM23 enhanced insertion of TIM23 into the inner membrane even in the absence of the soluble intermembrane space fraction. Together, these results demonstrate that the cleavable N-terminal extensions present on carrier proteins from plants are required for efficient insertion into the inner mitochondrial membrane, and that they can stimulate insertion of any carrier-like protein into the inner membrane.