Hira Daisuke, Matsumura Misa, Kitamura Ryuji, Furukawa Kenji, Fujii Takao
Department of Applied Life Science, Faculty of Biotechnology and Life Science, Sojo University, 4-22-1 Ikeda, Kumamoto, 860-0082, Japan.
Department of Applied Life Science, Faculty of Biotechnology and Life Science, Sojo University, 4-22-1 Ikeda, Kumamoto, 860-0082, Japan.
Biochem Biophys Res Commun. 2020 Jun 4;526(3):654-660. doi: 10.1016/j.bbrc.2020.03.144. Epub 2020 Apr 2.
Anaerobic ammonium oxidation (anammox) and denitrification are two different microbial reactions that form nitrogen gas. The initial step in the anammox reaction-reduction of nitrite to nitric oxide-is thought to be catalyzed by homologs of dissimilatory nitrite reductase, which is known to be involved in denitrification. Here, we reveal the crystal structure of the copper-containing nitrite reductase (CuNIR) of strain KSU-1, an anammox bacterium. CuNIR had a unique homohexameric structure with three disulfide bridges between homotrimers, although the trimer was similar to that of known CuNIRs. Kinetic and mutagenesis analyses suggested that the hexameric structure is important for the electron transfer reaction.
厌氧氨氧化（anammox）和反硝化作用是形成氮气的两种不同的微生物反应。厌氧氨氧化反应的初始步骤——将亚硝酸盐还原为一氧化氮——被认为是由异化亚硝酸盐还原酶的同源物催化的，而异化亚硝酸盐还原酶已知参与反硝化作用。在此，我们揭示了厌氧氨氧化细菌KSU-1菌株含铜亚硝酸盐还原酶（CuNIR）的晶体结构。CuNIR具有独特的同型六聚体结构，在同型三聚体之间有三个二硫键，尽管三聚体与已知的CuNIRs相似。动力学和诱变分析表明，六聚体结构对电子转移反应很重要。
