Histidine 416 of the periplasmic binding protein NikA is essential for nickel uptake in Escherichia coli |
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Authors: | Cavazza Christine Martin Lydie Laffly Emmanuelle Lebrette Hugo Cherrier Mickaël V Zeppieri Laura Richaud Pierre Carrière Marie Fontecilla-Camps Juan C |
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Affiliation: | Institut de Biologie Structurale Jean-Pierre Ebel, UMR 5075, CEA, CNRS, Université Joseph Fourier-Grenoble 1, Grenoble, France. christine.cavazza@ibs.fr |
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Abstract: | Escherichia coli require nickel for the synthesis of [NiFe] hydrogenases under anaerobic growth conditions. Nickel import depends on the specific ABC-transporter NikABCDE encoded by the nik operon, which deletion causes the complete abolition of hydrogenase activity. We have previously postulated that the periplasmic binding protein NikA binds a natural metallophore containing three carboxylate functions that coordinate a Ni(II) ion, the fourth ligand being His416, the only direct metal-protein contact, completing a square-planar coordination for the metal. The crystal structure of the H416I mutant showed no electron density corresponding to a metal-chelator complex. In vivo experiments indicate that the mutation causes a significant decrease in nickel uptake and hydrogenase activity. These results confirm the essential role of His416 in nickel transport by NikA. |
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