Site-directed mutagenesis reveals new and essential elements for iron-coordination of the sulfur oxygenase reductase from the acidothermophilic Acidianus tengchongensis

作     者：CHEN ZhiWei JIANG ChengYing LIU ShuangJiang 

作者机构：State Key Laboratory of Microbial Resources Institute of Microbiology Chinese Academy of Sciences Beijing 100101 China 

出 版 物：《Chinese Science Bulletin》 (Chin. Sci. Bull.)

年 卷 期：2009年第54卷第4期

页      面：652-657页

核心收录：

学科分类：0710[理学-生物学] 1007[医学-药学(可授医学、理学学位)] 100705[医学-微生物与生化药学] 07[理学] 071005[理学-微生物学] 10[医学] 

基　　金：Supported by National Natural Science Foundation of China (Grant Nos. 30670018, 30621005) State Key Basic Research and Development Program of China (Grant No. 2004CB719602) 

主　　题：嗜酸热古菌 硫加氧还原酶 突变形成分析 亚铁血红素 水菱钇矿 

摘      要：Previous study on refolding of sulfur oxygenase reductase (SOR) inclusion bodies from recombinant Escherichia coli showed that iron was critical to the activity of the SOR from Acidianus ambivalens. In this study, enzymatic assays showed that 2,2′-Dipyridyl, Tiron and 8-hydroxyquinoline, which are specific for chelating ferrous or ferric ions, strongly inhibited the activity of SOR from A. tengchongensis, suggesting that iron atom is essential for SOR activity. Alignment of several functionally identified SORs and SOR-like sequences from genome database revealed a conserved, putative iron binding motif, H86-X3-H90-Xn-E114-Xn-E129 (numbering according to the Acidianus tengchongensis SOR sequence). Three mutants of SOR were generated by site-directed mutagenesis of H86, H90 and E129 into phenyla-lanine or alanine residue in this study. Circular dichroism spectrum determination indicated that there was no change of the secondary structures of mutant SORs, H86F, H90F and E129A, but all mutants were completely inactive. Through determination of iron contents we found that SOR mutants of H86F, H90F and E129A completely or partially lost iron, while mutants of C31S, C101S, and C104S (generated in a previous study) did not. This result indicated that H86, H90 and E129 but not C31, C101, and C104 were involved in binding to iron atom. Based on this and previous studies, it is proposed that the conserved motifs, C31-Xn-C101-X2-C104 and H86-X3-H90-X23-E114-X14-(E/D)129, are respectively for sulfur and molecular oxygen binding and activation. These two conserved motifs are essential elements for the SOR activity.