Biochemical and crystallographic characterization of ferredoxin-NADP+ reductase from nonphotosynthetic tissues
Biochemical and crystallographic characterization of ferredoxin-NADP+ reductase from nonphotosynthetic tissues
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DOI：
10.1021/bi011224c
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发表时间：
2001-12-04
期刊：
影响因子：
2.9
通讯作者：
Zanetti, G
中科院分区：
文献类型：
--
作者：
Aliverti, A;Faber, R;Zanetti, G
不同形式的铁氧还蛋白-NADP(+) 还原酶在光合和非光合植物组织中表达。两种酶都催化 NADP(H) 和铁氧还蛋白之间的电子转移；而在叶子中，该酶在光合作用中将还原当量从光还原铁氧还蛋白转移到 NADP(+)，而在根中，它具有相反的生理作用，以 NADPH 为代价还原铁氧还蛋白，主要用于硝酸盐同化。在这里，分析了非光合异构体的结构和动力学特性，以确定可能与组织特异性功能相关的特征。与菠菜叶铁氧还蛋白-NADP+还原酶相比，重组玉米根亚型表现出吸收光谱略有改变、更高的等电点、对 NADP(+) 的亲和力高出 30 倍以上、对有限蛋白水解的敏感性更高，以及大约 20 mV 的正氧化还原电位。 1.7埃分辨率的晶体结构与光合组织中的铁氧还蛋白-NADP(+)还原酶的结构非常相似。该根铁氧还蛋白-NADP(+) 还原酶有四个不同的结构特征：结合的 FAD 分子的替代构象、氨基末端延伸的替代路径、FAD 结合结构域中的二硫键以及结合铁氧还蛋白的表面的变化。
Distinct forms of ferredoxin-NADP(+) reductase are expressed in photosynthetic and nonphotosynthetic plant tissues. Both enzymes catalyze electron transfer between NADP(H) and ferredoxin; whereas in leaves the enzyme transfers reducing equivalents from photoreduced ferredoxin to NADP(+) in photosynthesis, in roots it has the opposite physiological role, reducing ferredoxin at the expense of NADPH mainly for use in nitrate assimilation. Here, structural and kinetic properties of a nonphotosynthetic isoform were analyzed to define characteristics that may be related to tissue-specific function. Compared with spinach leaf ferredoxin-NADP+ reductase, the recombinant corn root isoform showed a slightly altered absorption spectrum, a higher pI, a > 30-fold higher affinity for NADP(+), greater susceptibility to limited proteolysis, and an similar to 20 mV more positive redox potential. The 1.7 Angstrom resolution crystal structure is very similar to the structures of ferredoxin-NADP(+) reductases from photosynthetic tissues. Four distinct structural features of this root ferredoxin-NADP(+) reductases are an alternate conformation of the bound FAD molecule, an alternate path for the amino-terminal extension, a disulfide bond in the FAD-binding domain, and changes in the surface that binds ferredoxin.