Replacement of Pro109 by His in TlpA, a thioredoxin‐like protein from Bradyrhizobium japonicum, alters its redox properties but not its in vivo functions

FEBS Letters

Rossmann, Reinhild²  Stern, Dorothee²  Hennecke, Hauke²  Jacobi, Alexander¹  Glockshuber, Rudi¹  Loferer, Hannes² 

[1] Institut für Molekularbiologie und Biophysik, Eidgenössische Technische Hochschule, CH-8092 Zürich, Switzerland;Mikrobiologisches Institut, Eidgenössische Technische Hochschule, CH-8092 Zürich, Switzerland

关键词: Bradyrhizobium japonicum;    Periplasm;    Redox potential;    Site-directed mutagenesis;    Thioredoxin;    DTT;    dithiothreitol;    GSH;    reduced glutathione;    GSSG;    glutathione disulfide (oxidized);    PDI;    protein disulfide isomerase;   

DOI  :  10.1016/S0014-5793(97)00270-6

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

TlpA, the membrane-anchored, thioredoxin-like protein from Bradyrhizobium japonicum, is essential for cytochrome aa ₃ biogenesis. The periplasmic domain of TlpA was previously shown to have protein thiol:disulfide oxidoreductase activity and reducing properties similar to those of cytoplasmic thioredoxins. Here, we replaced the proline-109 in its active-site sequence C¹⁰⁷V¹⁰⁸P¹⁰⁹C¹¹⁰ by a histidine residue. The resulting active-site motif (CVHC) resembles that of oxidizing thiol:disulfide oxidoreductases such as protein disulfide isomerase (PDI) and DsbA. Indeed, the TlpA variant P109H was by 66 mV more oxidizing than the wild-type protein. Nevertheless, the altered protein was even more efficient in catalyzing the reduction of insulin disulfides by dithiothreitol than the wild-type due to a faster recycling of its catalytically active, reduced form. Cells of B. japonicum expressing only the mutated tlpA gene had the same phenotypes as wild-type cells, suggesting that the change in the redox potential of TlpA was not critical for its in vivo function.

【 授权许可】

Unknown