Binding of Ni2+ to a histidine- and glutamine-rich protein, Hpn-like |
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Authors: | Yi-Bo Zeng Dong-Mei Zhang Hongyan Li Hongzhe Sun |
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Institution: | (1) Department of Chemistry and Open Laboratory of Chemical Biology, The University of Hong Kong, Pokfulam Road, Hong Kong, People’s Republic of China;(2) State Key Laboratory of Pharmaceutical Biotechnology, School of Life Science, Nanjing University, Nanjing, 210093, People’s Republic of China |
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Abstract: | Hpn-like (Hpnl) protein, encoded by the hpnl gene in Helicobacter pylori and featuring a histidine-rich and two glutamine-rich motifs, can render nickel tolerance to H. pylori when the external nickel level reaches toxic limits. We found that the recombinant Hpnl exists as an oligomer in the native
state and binds to two molar equivalents of nickel ions per monomer with a dissociation constant of 3.8 μM. Nickel could be
released from Hpnl either at acidic pH (pH1/2 4.6) or in the presence of chelate ligands, such as EDTA (t
1/2 = 220, 355, and 716 min at pH 6.0, 7.0, and 7.5, respectively). Our combined spectroscopic data show that nickel ion coordinates
to a nitrogen of a histidine residue possibly with a coordination number of four (square-planar geometry) or five. The growth
of Escherichia coli cells with or without the hpnl gene implied a protective role of Hpnl under higher concentrations of external nickel ions. Hpnl may serve a role in binding/storage
or detoxification of excess nickel ions.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Hpn-like Helicobacter pylori Histidine-rich Glutamine-rich Nickel binding |
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