Shatwell K P, Dancis A, Cross A R, Klausner R D, Segal A W
Department of Medicine, University College London, 5 University Street, London WC1E 6JJ, United Kingdom.
J Biol Chem. 1996 Jun 14;271(24):14240-4. doi: 10.1074/jbc.271.24.14240.
Plasma membrane preparations from strains of the yeast Saccharomyces cerevisiae gave a reduced minus oxidized spectrum characteristic of a b-type cytochrome and very similar to the spectrum of flavocytochrome b558 of human neutrophils. The magnitude of the signal correlated with the level of ferric reductase activity and the copy number of the FRE1 gene, indicating that the FRE1 protein is a cytochrome b. Sequence similarities with the flavin binding site of flavocytochrome b558 and other members of the ferredoxin-NADP reductase family, together with increased levels of noncovalently bound FAD and iodonitrotetrazolium violet reductase activity in membranes from a yeast strain overexpressing ferric reductase, suggested that the FRE1 protein may also carry a flavin group. Potentiometric titrations indicated that FRE1, like neutrophil NADPH oxidase, has an unusually low redox potential, in the region of -250 mV, and binds CO.
来自酿酒酵母菌株的质膜制剂呈现出b型细胞色素特有的还原态减去氧化态光谱，与人类中性粒细胞的黄素细胞色素b558光谱非常相似。信号强度与铁还原酶活性水平和FRE1基因的拷贝数相关，表明FRE1蛋白是一种细胞色素b。与黄素细胞色素b558的黄素结合位点和铁氧化还原蛋白-NADP还原酶家族其他成员的序列相似性，以及过表达铁还原酶的酵母菌株膜中与黄素腺嘌呤二核苷酸（FAD）非共价结合水平的增加和碘硝基四氮唑蓝还原酶活性的增加，表明FRE1蛋白可能也携带一个黄素基团。电位滴定表明，FRE1与中性粒细胞NADPH氧化酶一样，具有异常低的氧化还原电位，在-250 mV范围内，并能结合一氧化碳。
