Björnberg Olof, Efler Petr, Ebong Epie Denis, Svensson Birte, Hägglund Per
Enzyme and Protein Chemistry, Department of Systems Biology, Søltofts Plads, Building 224, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
Enzyme and Protein Chemistry, Department of Systems Biology, Søltofts Plads, Building 224, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
Arch Biochem Biophys. 2014 Dec 15;564:164-72. doi: 10.1016/j.abb.2014.09.010. Epub 2014 Sep 22.
Three protein disulfide reductases of the thioredoxin superfamily from the industrially important Gram-positive Lactococcus lactis (LlTrxA, LlTrxD and LlNrdH) are compared to the "classical" thioredoxin from Escherichia coli (EcTrx1). LlTrxA resembles EcTrx1 with a WCGPC active site motif and other key residues conserved. By contrast, LlTrxD is more distantly related and contains a WCGDC motif. Bioinformatics analysis suggests that LlTrxD represents a subgroup of thioredoxins from Gram-positive bacteria. LlNrdH is a glutaredoxin-like electron donor for ribonucleotide reductase class Ib. Based on protein-protein equilibria LlTrxA (E°'=-259mV) and LlNrdH (E°'=-238mV) show approximately 10mV higher standard state redox potentials than the corresponding E. coli homologues, while E°' of LlTrxD is -243mV, more similar to glutaredoxin than "classical" thioredoxin. EcTrx1 and LlTrxA have high capacity to reduce insulin disulfides and their exposed active site thiol is alkylated at a similar rate at pH 7.0. LlTrxD on the other hand, is alkylated by iodoacetamide at almost 100 fold higher rate and shows no activity towards insulin disulfides. LlTrxA, LlTrxD and LlNrdH are all efficiently reduced by NADPH dependent thioredoxin reductase (TrxR) from L. lactis and good cross-reactivity towards E. coli TrxR was observed with LlTrxD as the notable exception.
将来自具有重要工业价值的革兰氏阳性乳酸乳球菌的硫氧还蛋白超家族的三种蛋白质二硫键还原酶（LlTrxA、LlTrxD和LlNrdH）与来自大肠杆菌的“经典”硫氧还蛋白（EcTrx1）进行比较。LlTrxA与EcTrx1相似，具有WCGPC活性位点基序，其他关键残基也保守。相比之下，LlTrxD的亲缘关系更远，含有WCGDC基序。生物信息学分析表明，LlTrxD代表革兰氏阳性细菌硫氧还蛋白的一个亚组。LlNrdH是核糖核苷酸还原酶Ib类的一种谷氧还蛋白样电子供体。基于蛋白质-蛋白质平衡，LlTrxA（E°'=-259mV）和LlNrdH（E°'=-238mV）的标准态氧化还原电位比相应的大肠杆菌同系物高约10mV，而LlTrxD的E°'为-243mV，与谷氧还蛋白比“经典”硫氧还蛋白更相似。EcTrx1和LlTrxA具有高还原胰岛素二硫键的能力，并且它们暴露的活性位点硫醇在pH 7.0时以相似的速率被烷基化。另一方面，LlTrxD被碘乙酰胺烷基化的速率几乎高100倍，并且对胰岛素二硫键没有活性。LlTrxA、LlTrxD和LlNrdH都能被乳酸乳球菌依赖NADPH的硫氧还蛋白还原酶（TrxR）有效还原，并且观察到它们与大肠杆菌TrxR具有良好的交叉反应性，但LlTrxD是明显的例外。
