Crystallographic and spectroscopic evidence for high affinity binding of FeEDTA(H2O)- to the periplasmic nickel transporter NikA.
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 A 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.
Cherrier
Mickaël V
MV
Laboratoire de Cristallographie et de Cristallogenèse des Protéines and Laboratoire de Spectroscopie de Masse des Protéines, Institut de Biologie Structurale J.P. Ebel (CEA-CNRS-UJF), 41 rue Jules Horowitz, 38027 Grenoble Cedex 1, France.
Martin
Lydie
L
Cavazza
Christine
C
Jacquamet
Lilian
L
Lemaire
David
D
Gaillard
Jacques
J
Fontecilla-Camps
Juan C
JC
D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004492:Edetic Acid / Q000737:chemistry* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D005296:Ferrous Compounds / Q000737:chemistry* / Q000378:metabolism; D007501:Iron / Q000737:chemistry* / Q000378:metabolism; D013058:Mass Spectrometry; D009532:Nickel / Q000737:chemistry* / Q000378:metabolism; D019897:Periplasm / Q000737:chemistry; D017434:Protein Structure, Tertiary
D018528:ATP-Binding Cassette Transporters; D029968:Escherichia coli Proteins; D005296:Ferrous Compounds; C089849:nikA protein, E coli; C055526:Fe(II)-EDTA; D009532:Nickel; D004492:Edetic Acid; D007501:Iron