Crystallographic and Spectroscopic Evidence for High Affinity Binding of FeEDTA(H2O)- to the Periplasmic Nickel Transporter NikA

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• 作者：Mickaë ; l V. Cherrier ; Lydie Martin ; Christine Cavazza ; Lilian Jacquamet ; David Lemaire ; Jacques Gaillard ; and Juan C. Fontecilla-Camps
• 刊名：Journal of the American Chemical Society
• 出版年：2005
• 出版时间：July 20, 2005
• 年：2005
• 卷：127
• 期：28
• 页码：10075 - 10082
• 全文大小：456K
• 年卷期：v.127,no.28(July 20, 2005)
• ISSN：1520-5126

文摘

Because nickel is both essential and toxic to a great variety of organisms, its detection andtransport is highly regulated. In Escherichia coli and other related Gram-negative bacteria, high affinitynickel transport depends on proteins expressed by the nik operon. A central actor of this process is theperiplasmic NikA transport protein. A previous structural report has proposed that nickel binds to NikA asa pentahydrate species. However, both stereochemical considerations and X-ray absorption spectroscopicresults are incompatible with that interpretation. Here, we report the 1.8 Å resolution structure of NikA andshow that it binds FeEDTA(H₂O)^- with very high affinity. In addition, we provide crystallographic evidencethat a metal-EDTA complex was also bound to the previously reported NikA structure. Our observationsstrongly suggest that nickel transport in E. coli requires the binding of this metal ion to a metallophore thatbears significant resemblance to EDTA. They also provide a basis for the potential use of NikA in thebioremediation of toxic transition metals and the design of artificial metalloenzymes.