Sutherland Molly C, Rankin Joel A, Kranz Robert G
Department of Biology, Washington University , St. Louis, Missouri 63130, United States.
Biochemistry. 2016 Jun 7;55(22):3150-6. doi: 10.1021/acs.biochem.6b00427. Epub 2016 May 26.
Cytochromes c require covalent attachment of heme via two thioether bonds at conserved CXXCH motifs, a process accomplished in prokaryotes by eight integral membrane proteins (CcmABCDEFGH), termed System I. Heme is trafficked from inside the cell to outside (via CcmABCD) and chaperoned (holoCcmE) to the cytochrome c synthetase (CcmF/H). Purification of key System I pathway intermediates allowed the determination of heme redox potentials. The data support a model whereby heme is oxidized to form holoCcmE and subsequently reduced by CcmF/H for thioether formation, with Fe(2+) being required for attachment to CXXCH. Results provide insight into mechanisms for the oxidation and reduction of heme in vivo.
细胞色素c需要通过保守的CXXCH基序处的两个硫醚键将血红素共价连接，在原核生物中，这一过程由八个整合膜蛋白（CcmABCDEFGH）完成，称为系统I。血红素从细胞内部运输到外部（通过CcmABCD），并由伴侣蛋白（全CcmE）护送至细胞色素c合成酶（CcmF/H）。关键系统I途径中间体的纯化使得能够测定血红素的氧化还原电位。数据支持一种模型，即血红素被氧化形成全CcmE，随后被CcmF/H还原以形成硫醚，附着到CXXCH需要Fe(2+)。结果为体内血红素氧化和还原的机制提供了见解。
