PDF(Pubmed)
Abstract：
Thioredoxin reductases (TrxR) activate thioredoxins (Trx) that regulate the activity of diverse target proteins essential to prokaryotic and eukaryotic life. However, very little is understood of TrxR/Trx systems and redox control in methanogenic microbes from the domain Archaea (methanogens), for which genomes are abundant with annotations for ferredoxin:thioredoxin reductases [Fdx/thioredoxin reductase (FTR)] from group 4 of the widespread FTR-like family. Only two from the FTR-like family are characterized: the plant-type FTR from group 1 and FDR from group 6. Herein, the group 4 archetype (AFTR) from Methanosarcina acetivorans was characterized to advance understanding of the family and TrxR/Trx systems in methanogens. The modeled structure of AFTR, together with EPR and Mössbauer spectroscopies, supports a catalytic mechanism similar to plant-type FTR and FDR, albeit with important exceptions. EPR spectroscopy of reduced AFTR identified a transient [4Fe-4S]1+ cluster exhibiting a mixture of S = 7/2 and typical S = 1/2 signals, although rare for proteins containing [4Fe-4S] clusters, it is most likely the on-pathway intermediate in the disulfide reduction. Furthermore, an active site histidine equivalent to residues essential for the activity of plant-type FTR and FDR was found dispensable for AFTR. Finally, a unique thioredoxin system was reconstituted from AFTR, ferredoxin, and Trx2 from M. acetivorans, for which specialized target proteins were identified that are essential for growth and other diverse metabolisms.
摘要：
硫氧还蛋白还原酶(TrxR)激活硫氧还蛋白(Trx),其调节原核生物和真核生物所必需的多种靶蛋白的活性。然而,对来自古菌（产甲烷菌）领域的产甲烷微生物中的TrxR/Trx系统和氧化还原控制知之甚少，其中基因组丰富，具有铁氧还蛋白的注释：来自广泛的FTR样家族第4组的硫氧还蛋白还原酶[Fdx/硫氧还蛋白还原酶（FTR）]。仅表征了来自FTR样家族的两个：来自第1组的植物型FTR和来自第6组的FDR。在这里，来自甲烷杆菌的第4组原型（AFTR）的特征是增进对产甲烷菌家族和TrxR/Trx系统的理解。AFTR的建模结构，连同EPR和Mössbauer光谱,支持类似于植物型FTR和FDR的催化机理，尽管有重要的例外。还原的AFTR的EPR光谱鉴定出瞬态[4Fe-4S]1簇，表现出S=7/2和典型的S=1/2信号的混合，虽然含有[4Fe-4S]簇的蛋白质很少见，它很可能是二硫化物还原中的中间途径。此外，发现与植物型FTR和FDR活性必需的残基等效的活性位点组氨酸对于AFTR是不必要的。最后,从AFTR重建了一个独特的硫氧还蛋白系统，铁氧还蛋白,和来自M.acetivorans的Trx2，为此，确定了对生长和其他多样化代谢至关重要的特定靶蛋白。
