The Thioredoxin System Reduces Protein Persulfide Intermediates Formed during the Synthesis of Thio-Cofactors in Bacillus subtilis
The Thioredoxin System Reduces Protein Persulfide Intermediates Formed during the Synthesis of Thio-Cofactors in Bacillus subtilis
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DOI：
10.1021/acs.biochem.9b00045
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发表时间：
2019-04-09
期刊：
影响因子：
2.9
通讯作者：
Dos Santos, Patricia C.
中科院分区：
文献类型：
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作者：
Zheng, Chenkang;Guo, Selina;Dos Santos, Patricia C.
Fe-S簇和其他硫代辅助因子的生物合成需要氧化还原剂的参与。这些途径的一个共同特征是形成瞬时蛋白质过硫化物，其容易被体外反应中常用的人工还原剂还原。这些试剂调节生物合成反应的反应性和催化效率，并且在某些情况下，扭曲酶的动力学行为，绕过已知对这些体内途径的功能至关重要的硫受体。在这里，我们提供了枯草芽孢杆菌 Trx（硫氧还蛋白）系统对蛋白质结合的过硫化物中间体的选择性反应性的动力学证据。我们的结果表明，Trx 系统的氧化还原通量调节半胱氨酸脱硫酶测定中硫化物的产生速率。同样，Trx 系统的活性取决于过硫化物的形成速率，表明体外两个酶系统之间存在偶联反应方案。 TrxA（硫氧还蛋白）或TrxR（硫氧还蛋白还原酶）的失活会损害枯草芽孢杆菌中Fe-S酶的活性，表明Trx系统参与Fe-S簇代谢。令人惊讶的是，TrxA 的生化表征表明该酶能够协调 Fe-S 物质，从而导致其还原酶活性丧失。 TrxA 通过不稳定簇的协调而失活，结合其在硫转移途径中作为生理还原剂的作用，提出了氧化还原调节的模型。这些发现提供了氧化还原调节和铁硫代谢之间的潜在联系。
The biosynthesis of Fe-S clusters and other thio-cofactors requires the participation of redox agents. A shared feature in these pathways is the formation of transient protein persulfides, which are susceptible to reduction by artificial reducing agents commonly used in reactions in vitro. These agents modulate the reactivity and catalytic efficiency of biosynthetic reactions and, in some cases, skew the enzymes' kinetic behavior, bypassing sulfur acceptors known to be critical for the functionality of these pathways in vivo. Here, we provide kinetic evidence for the selective reactivity of the Bacillus subtilis Trx (thioredoxin) system toward protein-bound persulfide intermediates. Our results demonstrate that the redox flux of the Trx system modulates the rate of sulfide production in cysteine desulfurase assays. Likewise, the activity of the Trx system is dependent on the rate of persulfide formation, suggesting the occurrence of coupled reaction schemes between both enzymatic systems in vitro. Inactivation of TrxA (thioredoxin) or TrxR (thioredoxin reductase) impairs the activity of Fe-S enzymes in B. subtilis, indicating the involvement of the Trx system in Fe-S cluster metabolism. Surprisingly, biochemical characterization of TrxA reveals that this enzyme is able to coordinate Fe-S species, resulting in the loss of its reductase activity. The inactivation of TrxA through the coordination of a labile cluster, combined with its proposed role as a physiological reducing agent in sulfur transfer pathways, suggests a model for redox regulation. These findings provide a potential link between redox regulation and Fe-S metabolism.