The cymA gene, encoding a tetraheme c-type cytochrome, is required for arsenate respiration in Shewanella species
The cymA gene, encoding a tetraheme c-type cytochrome, is required for arsenate respiration in Shewanella species
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DOI：
10.1128/jb.01698-06
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发表时间：
2007-03-01
影响因子：
3.2
通讯作者：
Saltikov, Chad W.
中科院分区：
文献类型：
--
作者：
Murphy, Julie N.;Saltikov, Chad W.
在希瓦氏菌属菌株ANA-3中，砷酸盐作为末端电子受体的利用由双基因操纵子arrAB赋予，arrAB缺乏编码可溶性ArrAB蛋白复合物的膜锚定亚基的基因。对希瓦氏菌CN-32株的基因组序列分析表明，它也含有相同的arrAB操纵子，核苷酸同源性为100%。在这里，我们报告CN-32呼吸砷酸盐，这种代谢依赖于arrA和一个额外的基因编码的膜相关的四血红素C型细胞色素，cymA。ANA-3中cymA的缺失也消除了砷酸盐的生长和减少。CN-32和ANA-3的Delta cymA菌株对Fe（III）和Mn（IV）的还原产生负面影响，但对硝酸盐的生长没有影响。与CN-32 Delta cymA菌株不同，ANA-3的Delta cymA菌株中不存在富马酸盐上的生长。反式cymA的同源和异源互补都恢复了CN-32和ANA-3的Delta cymA菌株对砷酸盐的生长。cymA的转录模式表明，它是在厌氧条件下，在富马酸盐和砷酸盐的存在下诱导。硝酸盐生长的细胞表现出最高水平的cymA表达在两个野生型菌株。最后，在CN-32 CymA的四个CXXCH c-血红素结合基序中的每一个中的第一个Cys到Ser的定点诱变几乎消除了砷酸盐的生长和减少。总之，这些结果表明，砷酸盐呼吸和还原的生化机制需要ArrAB与膜相关四血红素细胞色素的相互作用，该细胞色素在非砷酸盐呼吸的希瓦氏菌属物种奥尼尔希瓦氏菌MR-1菌株中对Fe（III）具有多效性作用。、锰（IV）、二甲基亚砜、硝酸盐、亚硝酸盐和富马酸盐呼吸。
In Shewanella sp. strain ANA-3, utilization of arsenate as a terminal electron acceptor is conferred by a two-gene operon, arrAB, which lacks a gene encoding a membrane-anchoring subunit for the soluble ArrAB protein complex. Analysis of the genome sequence of Shewanella putrejaciens strain CN-32 showed that it also contained the same arrAB operon with 100% nucleotide identity. Here, we report that CN-32 respires arsenate and that this metabolism is dependent on arrA and an additional gene encoding a membrane-associated tetraheme c-type cytochrome, cymA. Deletion of cymA in ANA-3 also eliminated growth on and reduction of arsenate. The Delta cymA strains of CN-32 and ANA-3 negatively affected the reduction of Fe(III) and Mn(IV) but not growth on nitrate. Unlike the CN-32 Delta cymA strain, growth on fumarate was absent in the Delta cymA strain of ANA-3. Both homologous and heterologous complementation of cymA in trans restored growth on arsenate in Delta cymA strains of both CN-32 and ANA-3. Transcription patterns of cymA showed that it was induced under anaerobic conditions in the presence of fumarate and arsenate. Nitrate-grown cells exhibited the greatest level of cymA expression in both wild-type strains. Lastly, site-directed mutagenesis of the first Cys to Ser in each of the four CXXCH c-heme binding motifs of the CN-32 CymA nearly eliminated growth on and reduction of arsenate. Together, these results indicate that the biochemical mechanism of arsenate respiration and reduction requires the interactions of ArrAB with a membrane-associated tetraheme cytochrome, which in the non-arsenate-respiring Shewanella species Shewanella oneidensis strain MR-1, has pleiotropic effects on Fe(III), Mn(IV), dimethyl sulfoxide, nitrate, nitrite, and fumarate respiration.