Ragsdale S W, Ljungdahl L G
J Bacteriol. 1984 Jan;157(1):1-6. doi: 10.1128/jb.157.1.1-6.1984.
Ferredoxin, flavodoxin, and rubredoxin were purified to homogeneity from Clostridium formicoaceticum and characterized. Variation of the iron concentration of the growth medium caused substantial changes in the concentrations of ferredoxin and flavodoxin but not of rubredoxin. The ferredoxin has a molecular weight of 6,000 and is a four iron-four sulfur protein with eight cysteine residues. The spectrum is similar to that of other ferredoxins. The molar extinction coefficients are 22.6 X 10(3) and 17.6 X 10(3) at 280 and 390 nm, respectively. From 100 g wet weight of cells grown with 3.6 microM iron and with 40 microM iron, 5 and 20 mg offerredoxin were isolated, respectively. The molecular weight of rubredoxin is 5,800 and it contains one iron and four cysteines. The UV-visible absorption spectrum is dissimilar to those of other rubredoxins in that the 373 nm absorption peak is quite symmetric, lacking the characteristic 350-nm shoulder found in other rubredoxins. The flavodoxin is a 14,500-molecular-weight protein which contains 1 mol of flavin mononucleotide per mol of protein. It forms a stable, blue semiquinone upon light irradiation in the presence of EDTA or during enzymatic reduction. When cells were grown in low-iron medium, flavodoxin constituted at least 2% of the soluble cell protein; however, it was not detected in extracts of cells grown in high-iron medium. The rubredoxin and ferredoxin expressed during growth in low-iron and high-iron media are identical as judged by iron, inorganic sulfide, and amino acid analysis, as well as light absorption spectroscopy.
从甲酸乙酸梭菌中纯化出了铁氧化还原蛋白、黄素氧化还原蛋白和红素氧化还原蛋白，并对其进行了表征。生长培养基中铁浓度的变化导致铁氧化还原蛋白和黄素氧化还原蛋白的浓度发生显著变化，但红素氧化还原蛋白的浓度未变。铁氧化还原蛋白的分子量为6000，是一种含有八个半胱氨酸残基的四铁-四硫蛋白。其光谱与其他铁氧化还原蛋白相似。在280和390nm处的摩尔消光系数分别为22.6×10³和17.6×10³。从100克湿重的细胞中，分别在3.6微摩尔铁和40微摩尔铁的条件下培养，分离得到了5毫克和20毫克的铁氧化还原蛋白。红素氧化还原蛋白的分子量为5800，含有一个铁和四个半胱氨酸。其紫外可见吸收光谱与其他红素氧化还原蛋白不同，因为373nm处的吸收峰相当对称，没有其他红素氧化还原蛋白中特有的350nm肩峰。黄素氧化还原蛋白是一种分子量为14500的蛋白质，每摩尔蛋白质含有1摩尔黄素单核苷酸。在EDTA存在下光照或酶促还原过程中，它会形成稳定的蓝色半醌。当细胞在低铁培养基中生长时，黄素氧化还原蛋白至少占可溶性细胞蛋白的2%；然而，在高铁培养基中生长的细胞提取物中未检测到它。通过铁、无机硫化物和氨基酸分析以及光吸收光谱判断，在低铁和高铁培养基中生长期间表达的红素氧化还原蛋白和铁氧化还原蛋白是相同的。
