Institute of Microbiology and Genetics, Department of Biology, Technische Universität Darmstadt, Schnittspahnstr. 10, 64287 Darmstadt, Germany.
Mol Microbiol. 2011 Dec;82(6):1515-30. doi: 10.1111/j.1365-2958.2011.07906.x. Epub 2011 Nov 21.
Assimilatory and dissimilatory sulphite reductions are key reactions in the biogeochemical sulphur cycle and several distinct sirohaem-containing sulphite reductases have been characterized. Here, we describe that the Epsilonproteobacterium Wolinella succinogenes is able to grow by sulphite respiration (yielding sulphide) with formate as electron donor. Sulphite is reduced by MccA, a prototypical member of an emerging new class of periplasmic cytochrome c sulphite reductases that, phylogenetically, belongs to a multihaem cytochrome c superfamily whose members play crucial roles in the global sulphur and nitrogen cycles. Within this family, MccA represents an unconventional octahaem cytochrome c containing a special haem c group that is bound via two cysteine residues arranged in a unique CX(15)CH haem c binding motif. The phenotypes of numerous W.succinogenes mutants producing MccA variants underlined the structural importance of this motif. Several open reading frames of the mcc gene cluster were individually inactivated and characterization of the corresponding mutants indicated that the predicted iron-sulphur protein MccC, the putative quinol dehydrogenase MccD (a member of the NrfD/PsrC family) as well as a peptidyl-prolyl cis-trans isomerase, MccB, are essential for sulphite respiration. MccA synthesis in W. succinogenes was found to be induced by sulphite (but not by thiosulphate or sulphide) and repressed in the presence of fumarate or nitrate. Based on the results, a sophisticated model of respiratory sulphite reduction by the Mcc system is presented.
同化和异化亚硫酸盐还原是生物地球化学硫循环中的关键反应，已经有几种不同的含硫血红素亚硫酸盐还原酶被描述过。在这里，我们描述了变形菌 Wolinella succinogenes 能够通过亚硫酸盐呼吸（产生硫化物）和甲酸盐作为电子供体进行生长。亚硫酸盐由 MccA 还原，MccA 是新兴的周质细胞色素 c 亚硫酸盐还原酶的一个典型成员，从系统发育上看，它属于多血红素细胞色素 c 超家族，其成员在全球硫和氮循环中起着至关重要的作用。在这个家族中，MccA 代表一种非常规的八血红素细胞色素 c，含有一个特殊的血红素 c 基团，通过两个排列在独特的 CX(15)CH 血红素 c 结合基序中的半胱氨酸残基结合。大量产生 MccA 变体的 W.succinogenes 突变体的表型强调了这个基序的结构重要性。mcc 基因簇的几个开放阅读框被单独失活，对相应突变体的特征分析表明，预测的铁硫蛋白 MccC、假定的醌脱氢酶 MccD（NrfD/PsrC 家族的成员）以及肽基脯氨酰顺反异构酶 MccB，对于亚硫酸盐呼吸是必不可少的。在 W. succinogenes 中，发现 MccA 的合成被亚硫酸盐（但不是硫代硫酸盐或硫化物）诱导，而在富马酸盐或硝酸盐存在时被抑制。基于这些结果，提出了一个关于 Mcc 系统呼吸亚硫酸盐还原的复杂模型。
