Role of Nitrosomonas europaea NitABC iron transporter in the uptake of Fe3+-siderophore complexes
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- 作者：Neeraja Vajrala ; Luis A. Sayavedra-Soto ; Peter J. Bottomley and Daniel J. Arp
- 关键词：Nitrosomonas europaea ; Fe ; Iron ABC transporter ; Siderophores ; Ferrioxamine ; Ferrichrome ; Pyoverdine ; Enterobactin ; Aerobactin ; Fluorescently labeled siderophore
- 刊名：Archives of Microbiology
- 出版时间：November 2010
- 出版年：2010
- 期刊代码：22_0302-8933
- 类别：bio
- 卷：192
- 期：11
- 页码：899-908
- 数据来源：sp
摘要
Nitrosomonas europaea has a single three-gene operon (nitABC) encoding an iron ABC transporter system (NitABC). Phylogenetic analysis clustered the subunit NitB with Fe3+-ABC transporter permease components from other organisms. The N. europaea strain deficient in nitB (nitB::kan) grew well in either Fe-replete or Fe-limited media and in Fe-limited medium containing the catecholate-type siderophore, enterobactin or the citrate-based dihydroxamate-type siderophore, aerobactin. However, the nitB::kan mutant strain was unable to grow in Fe-limited media containing either the hydroxamate-type siderophores, ferrioxamine and ferrichrome or the mixed-chelating type siderophore, pyoverdine. Exposure of N. europaea cells to a ferrichrome analog coupled to the fluorescent moiety naphthalic diimide (Fhu-NI) led to increase in fluorescence in the wild type but not in nitB::kan mutant cells. Spheroplasts prepared from N. europaea wild type exposed to Fhu-NI analog retained the fluorescence, while spheroplasts of the nitB::kan mutant were not fluorescent. NitABC transports intact Fe3+-ferrichrome complex into the cytoplasm and is an atypical ABC type iron transporter for Fe3+ bound to ferrioxamine, ferrichrome or pyoverdine siderophores into the cytoplasm. The mechanisms to transport iron in either the Fe3+ or Fe2+ forms or Fe3+ associated with enterobactin or aerobactin siderophores into the cell across the cytoplasmic membrane are as yet undetermined.