Anammox Organism KSU-1 Expresses a Novel His/DOPA Ligated Cytochrome c
Anammox Organism KSU-1 Expresses a Novel His/DOPA Ligated Cytochrome c
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DOI：
10.1016/j.jmb.2018.02.017
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发表时间：
2018-04-13
影响因子：
5.6
通讯作者：
Fujii, Takao
中科院分区：
文献类型：
--
作者：
Hira, Daisuke;Kitamura, Ryuji;Fujii, Takao
厌氧氨氧化是一种细菌能量代谢过程，由亚硝酸盐和铵离子形成N-2气体。厌氧氨氧化的酶促机制已逐渐被揭示，然而，在厌氧氨氧化细菌的电子传递链仍然知之甚少。在本研究中，我们纯化和表征两个低分子量的C型细胞色素从厌氧氨氧化细菌菌株，KSU-1的富集培养。在KSU-1基因组中鉴定了它们的基因KSU1_B0428和KSU1_C0855，并鉴定了它们的重组蛋白。KSU1_B0428是一种典型的c型细胞色素，具有His/Met配位的血红素，充当电子转移蛋白。与此相反，KSU1_C0855不能被指定为一个已知的细胞色素，它的血红素被认为有一个不常见的轴向配体集。C 0855的晶体结构分析清楚地表明，它的血红素铁由作为第五配体的His 15配位。此外，Tyr 60的第6个配位位置被芳环占据，并发现了一个与芳碳不可分的电子密度，通过分子质量分析将该电子密度归属于0原子。因此，Tyr 60将被化学修饰为3，4-二羟基苯丙氨酸并与Fe原子结合。我们发现，厌氧氨氧化细菌菌株KSU-1表达一种新的细胞色素c，具有前所未有的His/3，4-二羟基苯丙氨酸配位血红素。新的c型细胞色素的表达可能是厌氧氨氧化过程的氧化还原反应所必需的。(C)2018爱思唯尔有限公司版权所有。
Anammox is a bacterial energy metabolic process that forms N-2 gas from nitrite and ammonium ions. The enzymatic mechanisms of anammox have been gradually revealed; however, the electron transport chain in anammox bacteria remains poorly understood. In the present study, we purified and characterized two low molecular-weight c-type cytochromes from an enriched culture of the anammox bacterium strain, KSU-1. Their genes, KSU1_B0428 and KSU1_C0855, were identified in the KSU-1 genome, and their recombinant proteins were characterized. KSU1_B0428 is a typical c-type cytochrome with a His/Met coordinated heme, acting as an electron transfer protein. In contrast, KSU1_C0855 could not be assigned as a known cytochrome and its heme was suggested to have an uncommon axial ligand set. Crystal structural analyses of C0855 clearly showed that its heme iron is coordinated by His15 as a fifth ligand. Moreover, the sixth coordination site is occupied by the aromatic ring of Tyr60, and an unassignable electron density that is inseparable with that of aromatic carbon of Tyr60 was found. The additional electron density was assigned to an 0 atom by molecular mass analyses. Therefore, Tyr60 would be chemically modified to 3,4-dihydroxyphenylalanine and bound to the Fe atom. We revealed that an anammox bacterium strain KSU-1 expresses a novel cytochrome c having an unprecedented His/3,4-dihydroxyphenylalanine coordinating heme. The expression of the novel c-type cytochrome might be required for the redox reaction of the anammox process. (C) 2018 Elsevier Ltd. All rights reserved.