IscA/SufA paralogues are required for the [4Fe-4S] cluster assembly in enzymes of multiple physiological pathways in Escherichia coli under aerobic growth conditions.
IscA/SufA paralogues are required for the [4Fe-4S] cluster assembly in enzymes of multiple physiological pathways in Escherichia coli under aerobic growth conditions.
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DOI：
10.1042/bj20090206
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发表时间：
2009-05-27
期刊：
影响因子：
--
通讯作者：
Ding H
中科院分区：
文献类型：
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作者：
Tan G;Lu J;Bitoun JP;Huang H;Ding H
IscA/SufA旁系同源物是大肠杆菌中铁硫簇组装机制的成员。尽管IscA或SufA的缺失对细胞生长仅具有轻微影响，但IscA和SufA两者的缺失导致在需氧生长条件下基本培养基中的零生长表型。在这里，我们报告了iscA/sufA双突变体（E.其中iscA和sufA都已在读码框内缺失的大肠杆菌菌株）可以通过补充支链氨基酸（BCAA）和硫胺素而部分恢复。我们进一步证明了IscA/SufA旁系同源物的缺失阻断了大肠杆菌中BCAA生物合成途径的IlvD（二羟酸脱氢酶）中的[4Fe-4S]簇组装。IscA/SufA能有效地促进[4Fe-4S]簇在IlvD中的组装并恢复酶的活性，表明IscA/SufA可能作为有氧条件下[4Fe-4S]簇组装的铁供体。进一步的研究表明，IscA/SufA也是硫胺素生物合成途径的蛋白质ThiC中的[4 Fe-4 S]簇组装、柠檬酸循环的顺乌头酸酶B和大肠杆菌DNA碱基切除修复途径的核酸内切酶III所必需的。大肠杆菌中。然而，IscA/SufA的缺失不会显著影响氧化还原转录因子SoxR、铁氧还蛋白和铁载体铁还原酶FhuF中的[2Fe-2S]簇组装。结果表明，[4Fe-4S]团簇和[2Fe-2S]团簇的生物起源可能有不同的途径，IscA/SufA旁系同源物对[4Fe-4S]团簇的组装是必需的，而对[2Fe-2S]团簇的组装是不必要的。大肠杆菌中。
IscA/SufA paralogs are the members of the iron-sulfur cluster assembly machinery in Escherichia coli. While deletion of either IscA or SufA has only a mild effect on cell growth, deletion of both IscA and SufA results in a null-growth phenotype in minimal medium under aerobic growth conditions. Here we report that cell growth of the iscA/sufA double mutant (E. coli strain in which both iscA and sufA had been in-frame-deleted) can be partially restored by supplementing with BCAAs (branched-chain amino acids) and thiamin. We further demonstrate that deletion of IscA/SufA paralogs blocks the [4Fe-4S] cluster assembly in IlvD (dihydroxyacid dehydratase) of the BCAA biosynthesis pathway in E. coli cells under aerobic conditions and that addition of the iron-bound IscA/SufA efficiently promotes the [4Fe-4S] cluster assembly in IlvD and restores the enzyme activity in vitro, suggesting that IscA/SufA may act as an iron donor for the [4Fe-4S] cluster assembly under aerobic conditions. Additional studies reveal that IscA/SufA are also required for the [4Fe-4S] cluster assembly in protein ThiC of the thiamin biosynthesis pathway, aconitase B of the citrate acid cycle, and endonuclease III of the DNA base excision repair pathway in E. coli under aerobic conditions. Nevertheless, deletion of IscA/SufA does not significantly affect the [2Fe-2S] cluster assembly in the redox transcription factor SoxR, ferredoxin, and the siderophore-iron reductase FhuF. The results suggest that the biogenesis of the [4Fe-4S] clusters and the [2Fe-2S] clusters may have distinct pathways and that IscA/SufA paralogs are essential for the [4Fe-4S] cluster assembly, but are dispensable for the [2Fe-2S] cluster assembly in E. coli under aerobic conditions.