Identification of protein transport complexes in the chloroplastic envelope membranes via chemical cross-linking.
Identification of protein transport complexes in the chloroplastic envelope membranes via chemical cross-linking.
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DOI：
10.1083/jcb.136.5.983
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发表时间：
1997-03-10
期刊：
影响因子：
--
通讯作者：
Keegstra K
中科院分区：
文献类型：
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作者：
Akita M;Nielsen E;Keegstra K
细胞质合成的蛋白质转运到叶绿体中使用存在于包膜中的进口机制。为了确定这一机制的组成部分，并开始研究这些组成部分在运输过程中如何相互作用，在完整的叶绿体上进行了化学交联，这些叶绿体含有在运输的特定阶段被ATP限制捕获的前体蛋白。使用三种不同的可逆同质双功能交联剂观察到大的交联配合物。三个外包膜蛋白（OEP86、OEP75和OEP34）和一个内包膜蛋白（IEP110）被鉴定为这些复合物的组成部分，这些蛋白先前被报道参与蛋白质的输入。除了这些膜蛋白外，hsp100家族的基质成员ClpC也存在于这些复合物中。我们认为ClpC作为分子伴侣，与其他成分合作完成前体蛋白进入叶绿体的运输。我们还提出，每个包膜都含有不同的易位复合物，即使在没有前体蛋白的情况下，这些复合物的一部分也会相互作用形成接触位点。
Transport of cytoplasmically synthesized proteins into chloroplasts uses an import machinery present in the envelope membranes. To identify the components of this machinery and to begin to examine how these components interact during transport, chemical cross-linking was performed on intact chloroplasts containing precursor proteins trapped at a particular stage of transport by ATP limitation. Large crosslinked complexes were observed using three different reversible homobifunctional cross-linkers. Three outer envelope membrane proteins (OEP86, OEP75, and OEP34) and one inner envelope membrane protein (IEP110), previously reported to be involved in protein import, were identified as components of these complexes. In addition to these membrane proteins, a stromal member of the hsp100 family, ClpC, was also present in the complexes. We propose that ClpC functions as a molecular chaperone, cooperating with other components to accomplish the transport of precursor proteins into chloroplasts. We also propose that each envelope membrane contains distinct translocation complexes and that a portion of these interact to form contact sites even in the absence of precursor proteins.