MOLECULAR-STRUCTURE OF THE OXIDIZED, RECOMBINANT, HETEROCYST [2FE-2S] FERREDOXIN FROM ANABAENA-7120 DETERMINED TO 1.7-ANGSTROM RESOLUTION
MOLECULAR-STRUCTURE OF THE OXIDIZED, RECOMBINANT, HETEROCYST [2FE-2S] FERREDOXIN FROM ANABAENA-7120 DETERMINED TO 1.7-ANGSTROM RESOLUTION
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DOI：
10.1021/bi00077a033
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发表时间：
1993-07-06
期刊：
影响因子：
2.9
通讯作者：
HOLDEN, HM
中科院分区：
文献类型：
--
作者：
JACOBSON, BL;CHAE, YK;HOLDEN, HM
鱼腥藻 7120 异形细胞中产生的 [2Fe-2S] 铁氧还蛋白在固氮中发挥着关键作用，它充当各种来源的电子受体和固氮酶的电子供体。这种铁氧还蛋白的三维结构现已确定并精炼至晶体学 R 值为 16.7%，所有测量的 X 射线数据都在 30.0 至 1.7 埃之间。这种铁氧还蛋白的分子基序与其他植物型铁氧还蛋白的分子基序相似，铁硫簇位于分子的外边缘，铁由无机硫和蛋白质半胱氨酰残基提供的硫四面体配位。该分子的整体二级结构由七股β折叠片、两个α螺旋和七个I型转角组成。特别令人感兴趣的是，被认为在非嗜盐铁氧还蛋白中绝对保守的 22 个氨基酸位置中的 4 个在该蛋白质的异形胞形式中是不同的。其中三个位置位于金属簇结合环中。
The [2Fe-2S] ferredoxin produced in the heterocyst cells of Anabaena 7120 plays a key role in nitrogen fixation, where it serves as an electron acceptor from various sources and an electron donor to nitrogenase. The three-dimensional structure of this ferredoxin has now been determined and refined to a crystallographic R value of 16.7%, with all measured X-ray data from 30.0 to 1.7 angstrom. The molecular motif of this ferredoxin is similar to that of other plant-type ferredoxins with the iron-sulfur cluster located toward the outer edge of the molecule and the irons tetrahedrally coordinated by both inorganic sulfurs and sulfurs provided by protein cysteinyl residues. The overall secondary structure of the molecule consists of seven strands of beta-pleated sheet, two alpha-helices, and seven type I turns. It is of special interest that 4 of the 22 amino acid positions thought to be absolutely conserved in nonhalophilic ferredoxins are different in the heterocyst form of the protein. Three of these positions are located in the metal-cluster binding loop.