ABC transporter-mediated release of a haem chaperone allows cytochrome c biogenesis
ABC transporter-mediated release of a haem chaperone allows cytochrome c biogenesis
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DOI：
10.1111/j.1365-2958.2006.05221.x
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发表时间：
2006-07-01
影响因子：
3.6
通讯作者：
Kranz, Robert G.
中科院分区：
文献类型：
--
作者：
Feissner, Robert E.;Richard-Fogal, Cynthia L.;Kranz, Robert G.
尽管所有王国的生物都有系统I或II细胞色素c生物发生途径，但为什么会有这两种不同的途径形成，仍然是一个谜。我们之前已经证明，系统I途径对血红素的亲和力高于系统II对细胞色素c生物合成的亲和力。在这里，我们展示了系统I途径可以在低水平利用血红素的机制。该机制包括一个ATP结合盒(ABC)转运体，它是释放周质血红素伴侣CCME到细胞色素c组装的最后一步所必需的。该ABC转运蛋白由ABC亚基CCMA和两种膜蛋白CCMB和CCMC组成。在没有CCMA或CCMB的情况下，HALO(HAEM)CCME以稳定的末端复合体与CCMC结合，表明HLOM与CCMC具有高亲和力。CCMA和CCMB的表达促进了CCMA(2)B(1)C(1)复合体的形成和依赖于ATP的holoCcmE的释放。我们认为CCMA(2)B(1)C(1)复合体代表了ABC转运蛋白超家族中一个新的亚群，其功能是释放伴侣。
Although organisms from all kingdoms have either the system I or II cytochrome c biogenesis pathway, it has remained a mystery as to why these two distinct pathways have developed. We have previously shown evidence that the system I pathway has a higher affinity for haem than system II for cytochrome c biogenesis. Here, we show the mechanism by which the system I pathway can utilize haem at low levels. The mechanism involves an ATP-binding cassette (ABC) transporter that is required for release of the periplasmic haem chaperone CcmE to the last step of cytochrome c assembly. This ABC transporter is composed of the ABC subunit CcmA, and two membrane proteins, CcmB and CcmC. In the absence of CcmA or CcmB, holo(haem)CcmE binds to CcmC in a stable dead-end complex, indicating high affinity binding of haem to CcmC. Expression of CcmA and CcmB facilitates formation of the CcmA(2)B(1)C(1) complex and ATP-dependent release of holoCcmE. We propose that the CcmA(2)B(1)C(1) complex represents a new subgroup within the ABC transporter superfamily that functions to release a chaperone.