Sulfite reduction in mycobacteria
Sulfite reduction in mycobacteria
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DOI：
10.1128/jb.00487-07
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发表时间：
2007-09-01
影响因子：
3.2
通讯作者：
Leyh, Thomas S.
中科院分区：
文献类型：
--
作者：
Pinto, Rachel;Harrison, Joseph S.;Leyh, Thomas S.
结核分枝杆菌给人类的福利带来了巨大的负担。它的生长能力和致病性与硫代谢有关，这被认为是开发抗生素的肥沃地区，特别是因为细菌中的许多硫获取步骤在宿主中没有发现。亚硫酸盐还原是一个这样的分支杆菌特异性步骤，是本论文的中心焦点。利用缺失诱变、代谢物筛选、互补和酶学相结合的方法研究了耻垢分枝杆菌亚硫酸盐的还原。在严格的厌氧条件下(k(cat) = 1.0（+/- 0.1）电子消耗/秒，k - M (SO3（))-2 = 27 (+/- 1) μ M）测定了从结核分枝杆菌中纯化的亚硫酸盐还原酶的初始速率参数，该酶没有检测到亚硝酸盐的周转，这在亚硫酸盐/亚硝酸盐还原酶家族中不必出现。亚硫酸盐还原酶（sirA，最初错误注释为nirA）的缺失表明，它是硫酸盐或亚硫酸盐作为唯一硫源生长所必需的，此外，细胞的亚硝酸盐还原活性无法以足够的速度还原亚硫酸盐以允许生长。像亚硝酸盐还原酶一样，亚硫酸盐还原酶也需要一个西血红素辅助因子来催化。Rv2393（重命名为che1）位于硫还原操纵子中，并首次被证明编码铁螯合酶，这是一种将Fe2+插入铁血红素的催化剂。che1的缺失导致细胞在需要亚硫酸盐还原酶活性的代谢物上生长缓慢。通过优化亚硝酸盐同化的生长条件，改善了这种缓慢生长的表型，这表明氮和硫的同化在铁螯合酶的合成和传递点重叠。
Mycobacterium tuberculosis places an enormous burden on the welfare of humanity. Its ability to grow and its pathogenicity are linked to sulfur metabolism, which is considered a fertile area for the development of antibiotics, particularly because many of the sulfur acquisition steps in the bacterium are not found in the host. Sulfite reduction is one such mycobacterium-specific step and is the central focus of this paper. Sulfite reduction in Mycobacterium smegmatis was investigated using a combination of deletion mutagenesis, metabolite screening, complementation, and enzymology. The initial rate parameters for the purified sulfite reductase from M. tuberculosis were determined under strict anaerobic conditions [k(cat) = 1.0 (+/- 0.1) electron consumed per second, and K-m(SO3())-2 = 27 (+/- 1) mu M], and the enzyme exhibits no detectible turnover of nitrite, which need not be the case in the sulfite/nitrite reductase family. Deletion of sulfite reductase (sirA, originally misannotated nirA) reveals that it is essential for growth on sulfate or sulfite as the sole sulfur source and, further, that the nitrite-reducing activities of the cell are incapable of reducing sulfite at a rate sufficient to allow growth. Like their nitrite reductase counterparts, sulfite reductases require a siroheme cofactor for catalysis. Rv2393 (renamed che1) resides in the sulfur reduction operon and is shown for the first time to encode a ferrochelatase, a catalyst that inserts Fe2+ into siroheme. Deletion of che1 causes cells to grow slowly on metabolites that require sulfite reductase activity. This slow-growth phenotype was ameliorated by optimizing growth conditions for nitrite assimilation, suggesting that nitrogen and sulfur assimilation overlap at the point of ferrochelatase synthesis and delivery.