A COMPONENT OF THE CHLOROPLASTIC PROTEIN IMPORT APPARATUS IS TARGETED TO THE OUTER ENVELOPE MEMBRANE VIA A NOVEL PATHWAY
A COMPONENT OF THE CHLOROPLASTIC PROTEIN IMPORT APPARATUS IS TARGETED TO THE OUTER ENVELOPE MEMBRANE VIA A NOVEL PATHWAY
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DOI：
10.1002/j.1460-2075.1995.tb07241.x
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发表时间：
1995-06-01
期刊：
影响因子：
11.4
通讯作者：
KEEGSTRA, K
中科院分区：
文献类型：
--
作者：
TRANEL, PJ;FROEHLICH, J;KEEGSTRA, K
75 kDa 的叶绿体外膜蛋白 (OEP75) 先前被鉴定为蛋白质输入机制的一个组成部分。在这里，我们提供了 OEP75 是蛋白质输入的一个组成部分的额外证据，提出了编码该蛋白质的 cDNA 克隆的分离，简要描述了其发育表达和组织特异性，并表征了其插入外被膜的特征。OEP75 被合成为较高分子量的前体 (prOEP75)，在体外输入测定中与分离的叶绿体结合，随后被加工成成熟形式 (mOEP75)。在此导入测定中，检测到了两种大小介于 prOEP75 和 mOEP75 之间的中间蛋白，在从豌豆幼叶中分离的叶绿体包膜中也检测到了其中一种中间体。 prOEP75 的结合和加工需要 ATP 和一种或多种表面暴露的蛋白质成分，并受到基质靶向蛋白 prSSU 的竞争。我们建议 prOEP75 转运肽的 N 末端充当基质靶向结构域，而该转运肽的中央疏水区域充当终止转移结构域。可能存在 prOEP75 的复杂插入和处理途径，以确保该输入组件的高保真度靶向。
A chloroplastic outer envelope membrane protein of 75 kDa (OEP75) was identified previously as a component of the protein import machinery. Here we provide additional evidence that OEP75 is a component of protein import, present the isolation of a cDNA clone encoding this protein, briefly describe its developmental expression and tissue specificity, and characterize its insertion into the outer envelope membrane, OEP75 was synthesized as a higher molecular weight precursor (prOEP75) which bound to isolated chloroplasts in an in vitro import assay and subsequently was processed to the mature form (mOEP75). During this import assay, two proteins intermediate in size between prOEP75 and mOEP75 were detected, One of these intermediates was also detected in chloroplast envelopes isolated from young pea leaves, Binding and processing of prOEP75 required ATP and one or more surface-exposed proteinaceous components, and was competed by prSSU, a stromal-targeted protein. We propose that the N-terminus of the prOEP75 transit peptide acts as a stromal-targeting domain and a central, hydrophobic region of this transit peptide acts as a stop-transfer domain. A complex route of insertion and processing of prOEP75 may exist to ensure high fidelity targeting of this import component.