Bricio C, Alvarez L, San Martin M, Schurig-Briccio L A, Gennis R B, Berenguer J
Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, Madrid, Spain.
Department of Biochemistry, University of Illinois, Urbana, Illinois, USA.
Appl Environ Microbiol. 2014 Aug;80(16):4871-8. doi: 10.1128/AEM.00790-14. Epub 2014 Jun 6.
Reduction of NO to N2O by denitrifiying bacteria is catalyzed either by a monomeric quinol-nitric oxide reductase (qNor) or by a heterodimeric cytochrome c-dependent nitric oxide reductase (cNor). In ancient thermophilic bacteria belonging to the Thermales and Aquificales phylogenetic groups, the cluster encoding the cNor includes a small third gene (norH), in addition to those encoding homologues to the subunits of a typical cNor (norC and norB). We show in Thermus thermophilus that the three genes are cotranscribed in a single mRNA from an inducible promoter. The isolation of individual nor mutants and the production in vivo of His-tagged NorH protein followed by immobilized-metal affinity chromatography (IMAC) allowed us to conclude that NorH constitutes a third subunit of the cNor from T. thermophilus, which is involved in denitrification in vivo, likely allowing more efficient electron transport to cNor.
反硝化细菌将一氧化氮还原为一氧化二氮的过程，要么由单体喹啉-一氧化氮还原酶（qNor）催化，要么由异源二聚体细胞色素c依赖性一氧化氮还原酶（cNor）催化。在属于嗜热菌纲和产水菌纲系统发育组的古老嗜热细菌中，编码cNor的基因簇除了包含编码典型cNor亚基（norC和norB）同源物的基因外，还包括一个小的第三个基因（norH）。我们在嗜热栖热菌中发现，这三个基因从一个可诱导启动子转录成单个mRNA。通过分离单个nor突变体并在体内产生带有His标签的NorH蛋白，随后进行固定化金属亲和层析（IMAC），我们得出结论，NorH构成嗜热栖热菌cNor的第三个亚基，它在体内参与反硝化作用，可能使电子向cNor的传递更高效。
