Binding of Ni2+ to a histidine- and glutamine-rich protein, Hpn-like.
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 microM. Nickel could be released from Hpnl either at acidic pH (pH(1/2) 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.
Zeng
Yi-Bo
YB
Department of Chemistry and Open Laboratory of Chemical Biology, The University of Hong Kong, Pokfulam Road, Hong Kong, People's Republic of China.
Zhang
Dong-Mei
DM
Li
Hongyan
H
Sun
Hongzhe
H
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001059:Apoproteins / Q000737:chemistry / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects; D003001:Cloning, Molecular; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000166:cytology / Q000187:drug effects / Q000235:genetics; D015870:Gene Expression; D005973:Glutamine; D016480:Helicobacter pylori / Q000378:metabolism*; D006639:Histidine; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009532:Nickel / Q000378:metabolism* / Q000494:pharmacology; D011485:Protein Binding; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013379:Substrate Specificity
D001059:Apoproteins; D001426:Bacterial Proteins; D005973:Glutamine; D006639:Histidine; D009532:Nickel