Armengaud J, Meyer C, Jouanneau Y
Laboratoire de Biochimie Microbienne (CNRS URA 1130, alliée à l'INSERM), Départment de Biologie Moléculaire et Structurale, Grenoble, France.
Biochem J. 1994 Jun 1;300 ( Pt 2)(Pt 2):413-8. doi: 10.1042/bj3000413.
A gene called fdxD that could potentially code for a ferredoxin has recently been identified upstream of the nitrogenase structural genes in Rhodobacter capsulatus [Willison, Pierrard and Hübner (1993) Gene 133, 39-46]. In the present study, the fdxD gene product has been overproduced in Escherichia coli in a soluble form. The recombinant protein, pink in colour, was purified to homogeneity, and biochemically characterized as a new ferredoxin. It represents the fifth ferredoxin so far identified in R. capsulatus and was designated FdV. Its N-terminal sequence is identical with that of the native ferredoxin isolated from R. capsulatus. U.v-visible-absorption spectra as well as results of c.d. and e.p.r. spectroscopy demonstrated that the fdxD product contained a [2Fe-2S] cluster correctly assembled and incorporated into the polypeptide. Although similar to plant-type ferredoxins, FdV appeared poorly competent in the photo-reduction of NADP+. On the basis of in vitro assays, FdV cannot serve as an electron donor for nitrogenase. The lack of reactivity of FdV in either of these assays may primarily be due to its relatively high mid-point redox potential (E'o = -220 mV, pH 7.5).
最近在荚膜红细菌固氮酶结构基因的上游发现了一个名为fdxD的基因，它可能编码一种铁氧化还原蛋白[威利森、皮埃尔拉德和许布纳（1993年），《基因》第133卷，第39 - 46页]。在本研究中，fdxD基因产物已在大肠杆菌中以可溶形式过量表达。这种重组蛋白呈粉红色，被纯化至同质，并经生化鉴定为一种新的铁氧化还原蛋白。它是迄今为止在荚膜红细菌中鉴定出的第五种铁氧化还原蛋白，被命名为FdV。其N端序列与从荚膜红细菌中分离出的天然铁氧化还原蛋白的N端序列相同。紫外可见吸收光谱以及圆二色光谱和电子顺磁共振光谱的结果表明，fdxD产物含有一个正确组装并整合到多肽中的[2Fe - 2S]簇。尽管FdV与植物型铁氧化还原蛋白相似，但它在光还原NADP⁺方面表现不佳。基于体外测定，FdV不能作为固氮酶的电子供体。FdV在这两种测定中缺乏反应性可能主要是由于其相对较高的中点氧化还原电位（E'o = -220 mV，pH 7.5）。
