Crystallographic and Spectroscopic Evidence for High Affinity Binding of FeEDTA(H2O)-to the Periplasmic Nickel Transporter NikA
- 15 June 2005
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 127 (28) , 10075-10082
- https://doi.org/10.1021/ja0518530
Abstract
Because nickel is both essential and toxic to a great variety of organisms, its detection and transport is highly regulated. In Escherichia coli and other related Gram-negative bacteria, high affinity nickel transport depends on proteins expressed by the nik operon. A central actor of this process is the periplasmic NikA transport protein. A previous structural report has proposed that nickel binds to NikA as a pentahydrate species. However, both stereochemical considerations and X-ray absorption spectroscopic results are incompatible with that interpretation. Here, we report the 1.8 Å resolution structure of NikA and show that it binds FeEDTA(H2O)- with very high affinity. In addition, we provide crystallographic evidence that a metal−EDTA complex was also bound to the previously reported NikA structure. Our observations strongly suggest that nickel transport in E. coli requires the binding of this metal ion to a metallophore that bears significant resemblance to EDTA. They also provide a basis for the potential use of NikA in the bioremediation of toxic transition metals and the design of artificial metalloenzymes.Keywords
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