The thioredoxin reductase system of mycoplasmas
The thioredoxin reductase system of mycoplasmas
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DOI：
10.1099/00221287-143-6-1933
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发表时间：
1997-06-01
期刊：
影响因子：
2.8
通讯作者：
Rottem, S
中科院分区：
文献类型：
--
作者：
BenMenachem, G;Himmelreich, R;Rottem, S
软体动物的代表物种拥有由低分子质量硫氧还蛋白（TRX）和NADPH结合硫氧还蛋白还原酶（NTR）组成的硫氧还蛋白还原酶系统（NTS），肺炎支原体和山羊支原体的TRX分子量分别为11.2和12 kDa，在90℃下稳定10分钟，两者TRX 与针对枯草芽孢杆菌 TRX 产生的单特异性多克隆抗体发生反应，但不与抗大肠杆菌 TRX 抗血清发生反应。山羊支原体和肺炎支原体NTR经过部分纯化，发现对同源TRX有活性，但对枯草芽孢杆菌或大肠杆菌的TRX没有活性，NTS活性的最佳pH值为6.5-7.5，并且依赖于NADPH作为电子供体，这是NADH无法满足的要求，编码肺炎支原体的TRX和NTR（trxA和trxB）的基因克隆测序，对trxA预测氨基酸序列进行比对分析，结果显示，11.2kDa蛋白（102个aa）与其他已知trxA基因产物具有26-68%的序列相似性，并含有保守的活性位点Cys-Gly-Pro-Cys，trxB的预测氨基酸序列含有315个残基，具有保守的NADPH结合结构域和FAD结合结构域I和II，与其他NTR相比，半胱氨酸二硫醇氧化还原活性区的活性位点具有异亮氨酸而不是苏氨酸。支原体中NTS的高活性表明支原体可能已经进化出NTS来保护自己免受自身产生的氧化挑战的后果。
Representative species of the Mollicutes possess a thioredoxin reductase system (NTS) composed of a low-molecular-mass thioredoxin (TRX) and NADPH-binding thioredoxin reductase (NTR), The TRXs of Mycoplasma pneumoniae and M. capricolum have molecular masses of 11.2 and 12 kDa, respectively, and are stable at 90 degrees C for 10 min, Both TRXs reacted with monospecific polyclonal antibodies generated against the Bacillus subtilis TRX, but not with anti-Escherichia coli TRX antisera. The M. capricolum and M. pneumoniae NTRs were partially purified and were found to be active with the homologous TRX, but not with the TRX of B. subtilis or E. coli, The NTS activity had an optimal ph of 6.5-7.5 and was dependent on NADPH as an electron donor, a requirement which could not be fulfilled by NADH, The genes encoding the TRX and NTR (trxA and trxB) of M. pneumoniae were cloned and sequenced, The comparative analysis of the predicted amino acid sequence of trxA showed that the 11.2 kDa protein (102 aa) shared 26-68% sequence similarity with products of other known trxA genes and contained the conserved active site Cys-Gly-Pro-Cys, The predicted amino acid sequence of trxB contained 315 residues with a conserved NADPH binding domain and FAD binding domains I and Il, The cysteine dithiol redox active region had isoleucine rather than threonine at the active site, as compared with other NTRs, The high activity of the NTS in mycoplasmas suggests that mycoplasmas may have evolved the NTS to protect themselves from the consequences of their self-generated oxidative challenge.