Loss of ATP hydrolysis activity by CcmAB results in loss of c-type cytochrome synthesis and incomplete processing of CcmE
Loss of ATP hydrolysis activity by CcmAB results in loss of c-type cytochrome synthesis and incomplete processing of CcmE
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DOI：
10.1111/j.1742-4658.2007.05769.x
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发表时间：
2007-05-01
期刊：
影响因子：
5.4
通讯作者：
Stevens, Julie M.
中科院分区：
文献类型：
--
作者：
Christensen, Olaf;Harvat, Edgar M.;Stevens, Julie M.
CCMA和CCMB蛋白长期以来被认为是细胞色素c在大肠杆菌中成熟所必需的。我们已经纯化了这些蛋白的一个复合体，并发现它具有ATP水解性。CCMA具有可溶性ATP水解亚单位的特征，只有当CCMB存在于膜上时，才能在膜结合的复合体中发现CCMA。CCMA(K40D)中Walker A基序的突变导致体外ATPase活性丧失和体内细胞色素c生物合成丧失。相同的突变不能阻止血红素与血红素伴侣CCME的共价结合，但由于某种不明原因，Holo-CCME不能将血红素转移到细胞色素c上，也不能作为可溶性变体释放到周质中。将外源血红素添加到具有CCMA缺失的血红素渗透性大肠杆菌中并不能恢复细胞色素c的产生。我们的结果表明，CcmAB在CCME处理亚铁血红素的过程中发挥了作用，这是一个复杂的化学结构，涉及一个不寻常的组氨酸-亚铁血红素共价键。
The proteins CcmA and CcmB have long been known to be essential for cytochrome c maturation in Escherichia coli. We have purified a complex of these proteins, and found it to have ATP hydrolysis activity. CcmA, which has the features of a soluble ATP hydrolysis subunit, is found in a membrane-bound complex only when CcmB is present in the membrane. Mutation of the Walker A motif in CcmA(K40D) results in loss of the in vitro ATPase activity and in loss of cytochrome c biogenesis in vivo. The same mutation does not prevent covalent attachment of heme to the heme chaperone CcmE, but holo-CcmE is, for some unidentified reason, incompetent for heme transfer to an apocytochrome c or for release into the periplasm as a soluble variant. Addition of exogenous heme to heme-permeable E. coli with a ccmA deletion did not restore cytochrome c production. Our results suggest a role for CcmAB in the handling of heme by CcmE, which is chemically complex and involves an unusual histidine-heme covalent bond.