Max Planck Institute of Biophysics, Department of Molecular Membrane Biology, Max-von-Laue-Str. 3, D-60438 Frankfurt am Main, Germany.
Biochim Biophys Acta Bioenerg. 2017 Mar;1858(3):231-238. doi: 10.1016/j.bbabio.2016.12.006. Epub 2016 Dec 20.
The Cbb-type cytochrome c oxidases (Cbb-CcOs), the second most abundant CcOs, catalyze the reduction of molecular oxygen to water, even at micromolar oxygen concentrations. In Pseudomonas stutzeri ZoBell, two tandemly organized cbb-operons encode the isoforms Cbb-1 and Cbb-2 both possessing subunits CcoN, CcoO and CcoP. However, only the cbb-2 operon contains an additional ccoQ gene. CcoQ consists of 62 amino acids and is predicted to possess one transmembrane spanning helix. The physiological role of CcoQ was investigated based on a CcoQ-deletion mutant and wild-type Cbb-2 crystals not containing subunit CcoQ. Cbb-2 isolated from the deletion mutant is inactive and appears as a dispersed band on blue native-PAGE gels. Surprisingly, in the absence of ccoQ, Cbb-1 also shows a strongly reduced activity. Our data suggest that CcoQ primarily functions as an assembly factor for Cbb-2 but is also required for correct assembly of Cbb-1. In contrast, once correctly assembled, Cbb-1 and Cbb-2 possess a full enzymatic activity even in the absence of CcoQ.
Cbb 型细胞色素 c 氧化酶（Cbb-CcOs）是第二丰富的 CcOs，即使在微摩尔氧浓度下，也能催化分子氧还原为水。在恶臭假单胞菌 ZoBell 中，两个串联组织的 cbb 操纵子编码同工型 Cbb-1 和 Cbb-2，它们都具有亚基 CcoN、CcoO 和 CcoP。然而，只有 cbb-2 操纵子包含一个额外的 ccoQ 基因。CcoQ 由 62 个氨基酸组成，预计具有一个跨膜螺旋。基于 CcoQ 缺失突变体和不含有亚基 CcoQ 的野生型 Cbb-2 晶体，研究了 CcoQ 的生理作用。从缺失突变体中分离出的 Cbb-2 是无活性的，并且在蓝色非变性 PAGE 凝胶上显示为分散的条带。令人惊讶的是，在没有 ccoQ 的情况下，Cbb-1 的活性也明显降低。我们的数据表明，CcoQ 主要作为 Cbb-2 的组装因子发挥作用，但也需要正确组装 Cbb-1。相比之下，一旦正确组装，即使没有 CcoQ，Cbb-1 和 Cbb-2 也具有完整的酶活性。
