Grabau C, Schatt E, Jouanneau Y, Vignais P M
Laboratoire de Biochimie Microbienne/LBIO/DBMS, Centre d'Etudes Nucléaires de Grenoble-85X, France.
J Biol Chem. 1991 Feb 15;266(5):3294-9.
A 285-base pair open reading frame was found immediately upstream of the fdxN gene (encoding ferredoxin I) of Rhodobacter capsulatus and coded for a 95-amino acid protein with a predicted molecular weight of 10,156. The deduced amino acid sequence contained 5 cysteines, 4 of which exhibited spacing characteristic of [2Fe-2S] plant and cyanobacterial ferredoxins. The amino acid sequence was found to share approximately 25% amino acid similarity with plant-type ferredoxins. The gene was named fdxC. Expression of the fdxC and fdxN genes together in Escherichia coli was accomplished by subcloning the genes in the vector pUC18 downstream of the lac promoter. Cells containing this plasmid produced a red and a brown protein corresponding to the fdxC and fdxN gene products, respectively. EPR and UV-visible absorption spectroscopy confirmed that the FdxC protein contained a [2Fe-2S] cluster and the FdxN protein contained two [4Fe-4S] clusters and that the centers were correctly assembled and inserted in the ferredoxins expressed in E. coli. Transcription (Northern blot) analysis showed that the genes were transcribed only under nitrogen-limiting (nif-derepressing) growth conditions.
在荚膜红细菌的fdxN基因（编码铁氧化还原蛋白I）上游紧邻处发现了一个285个碱基对的开放阅读框，它编码一个95个氨基酸的蛋白质，预测分子量为10156。推导的氨基酸序列含有5个半胱氨酸，其中4个呈现出[2Fe-2S]植物型和蓝细菌铁氧化还原蛋白的间隔特征。发现该氨基酸序列与植物型铁氧化还原蛋白具有约25%的氨基酸相似性。该基因被命名为fdxC。通过将基因亚克隆到载体pUC18中lac启动子下游，实现了fdxC和fdxN基因在大肠杆菌中的共表达。含有该质粒的细胞分别产生了对应于fdxC和fdxN基因产物的红色和棕色蛋白质。电子顺磁共振（EPR）和紫外可见吸收光谱证实，FdxC蛋白含有一个[2Fe-2S]簇，FdxN蛋白含有两个[4Fe-4S]簇，且这些中心在大肠杆菌中表达的铁氧化还原蛋白中正确组装并插入。转录（Northern印迹）分析表明，这些基因仅在氮限制（nif去阻遏）生长条件下转录。
