Kirtania Prithwiraj, Bhattacharya Bidisha, Das Gupta Sujoy K
Department of Microbiology, Bose Institute, Kolkata, India.
FEMS Microbiol Lett. 2014 Aug;357(1):16-22. doi: 10.1111/1574-6968.12502. Epub 2014 Jul 2.
Mycobacteriophage L5 gene 56 encodes a putative thioredoxin family protein. Phylogenetic analysis revealed that Gp56 and related proteins are distantly related to NrdH - a glutaredoxin homolog which has thioredoxin-like properties. To understand its function, the recombinant version of the protein was biochemically characterized. For the sake of comparison, a mycobacterial thioredoxin, TrxB, was included in the study. Results show that Gp56 can be reduced by dithiothreitol, but only at a higher concentration as compared with TrxB, indicating that the standard redox potential of Gp56 is lower than that of TrxB. The reduced protein can subsequently act as a reductant of protein disulfide bonds. Gp56 can be reduced by NADPH with the help of thioredoxin reductase (TrxR) but less efficiently as compared with TrxB. The abilities of Gp56 and TrxB to reduce Gp50, the L5-encoded ribonucleotide reductase, was examined. While both are capable of executing this function, the former needs more reducing equivalents in the process as compared with the latter. This study shows that L5Gp56 represents a new class of NrdH-like proteins that function optimally in a reducing environment.
分枝杆菌噬菌体L5的基因56编码一种假定的硫氧还蛋白家族蛋白。系统发育分析表明，Gp56及相关蛋白与NrdH（一种具有硫氧还蛋白样特性的谷氧还蛋白同源物）有较远的亲缘关系。为了解其功能，对该蛋白的重组形式进行了生化特性分析。为作比较，研究中纳入了一种分枝杆菌硫氧还蛋白TrxB。结果显示，二硫苏糖醇可使Gp56还原，但与TrxB相比，所需浓度更高，这表明Gp56的标准氧化还原电位低于TrxB。还原后的蛋白随后可作为蛋白质二硫键的还原剂。在硫氧还蛋白还原酶（TrxR）的帮助下，NADPH可使Gp56还原，但与TrxB相比效率较低。研究了Gp56和TrxB还原L5编码的核糖核苷酸还原酶Gp50的能力。虽然二者都能执行此功能，但与后者相比，前者在此过程中需要更多的还原当量。本研究表明，L5Gp56代表了一类新的NrdH样蛋白，在还原环境中功能最佳。
