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- Publisher Website: 10.1042/BJ20051160
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- PMID: 16164421
- WOS: WOS:000234412400029
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Article: Expression and characterization of a histidine-rich protein, Hpn: Potential for Ni2+ storage in Helicobacter pylori
Title | Expression and characterization of a histidine-rich protein, Hpn: Potential for Ni2+ storage in Helicobacter pylori |
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Authors | |
Keywords | Helicobacter pylori Histidine-rich protein Hpn Nickel Storage |
Issue Date | 2006 |
Publisher | Portland Press Ltd. The Journal's web site is located at http://www.biochemj.org |
Citation | Biochemical Journal, 2006, v. 393 n. 1, p. 285-293 How to Cite? |
Abstract | Hpn is a small cytoplasmic protein found in Helicobacter pylori, which binds Ni2+ ions with moderate affinity. Consisting of 60 amino acids, the protein is rich in histidine (28 residues, 46.7%), as well as glutamate, glycine and serine residues (in total 31.7%), and contains short repeating motifs. In the present study, we report the detailed biophysical characterization of the multimeric status and Ni2+-binding properties of purified recombinant Hpn under physiologically relevant conditions. The protein exists as an equilibration of multimeric forms in solution, with 20-mers (approx. 136 kDa) being the predominant species. Using equilibrium dialysis, ICP-MS (inductively coupled plasma MS) and UV/visible spectroscopy, Hpn was found to bind five Ni2+ ions per monomer at pH 7.4, with a dissociation constant (Kd) of 7.1 μM. Importantly, Ni2+ binding to Hpn is reversible: metal is released either in the presence of a chelating ligand such as EDTA, or at a slightly acidic pH (pH for half dissociation, pH1/2 ∼6.3). Ni2+ binding induces conformational changes within the protein, increasing β-sheet and reducing α-helical content, from 22% to 37%, and 20% to 10% respectively. Growth curves of Escherichia coli BL21(DE3) both with and without the hpn gene performed under Ni2+ pressure clearly implied a role for Hpn to protect the cells from higher concentrations of external metal ions. Similarly, the accumulation of Ni2+ in these cells expressing Hpn from a plasmid was approx. 4-fold higher than in uninduced controls or control cultures that lacked the plasmid. Similarly, levels of Ni2+ in wild-type H. pylori 26695 cells were higher than those in H. pylori hpn-deletion mutant strains. Hpn may potentially serve multiple roles inside the bacterium: storage of Ni 2+ ions in a 'reservoir'; donation of Ni2+ to other proteins; and detoxification via sequestration of excess Ni2+. © 2006 Biochemical Society. |
Persistent Identifier | http://hdl.handle.net/10722/68093 |
ISSN | 2023 Impact Factor: 4.4 2023 SCImago Journal Rankings: 1.612 |
PubMed Central ID | |
ISI Accession Number ID | |
References |
DC Field | Value | Language |
---|---|---|
dc.contributor.author | Ge, R | en_HK |
dc.contributor.author | Watt, RM | en_HK |
dc.contributor.author | Sun, X | en_HK |
dc.contributor.author | Tanner, JA | en_HK |
dc.contributor.author | He, QY | en_HK |
dc.contributor.author | Huang, JD | en_HK |
dc.contributor.author | Sun, H | en_HK |
dc.date.accessioned | 2010-09-06T06:01:16Z | - |
dc.date.available | 2010-09-06T06:01:16Z | - |
dc.date.issued | 2006 | en_HK |
dc.identifier.citation | Biochemical Journal, 2006, v. 393 n. 1, p. 285-293 | en_HK |
dc.identifier.issn | 0264-6021 | en_HK |
dc.identifier.uri | http://hdl.handle.net/10722/68093 | - |
dc.description.abstract | Hpn is a small cytoplasmic protein found in Helicobacter pylori, which binds Ni2+ ions with moderate affinity. Consisting of 60 amino acids, the protein is rich in histidine (28 residues, 46.7%), as well as glutamate, glycine and serine residues (in total 31.7%), and contains short repeating motifs. In the present study, we report the detailed biophysical characterization of the multimeric status and Ni2+-binding properties of purified recombinant Hpn under physiologically relevant conditions. The protein exists as an equilibration of multimeric forms in solution, with 20-mers (approx. 136 kDa) being the predominant species. Using equilibrium dialysis, ICP-MS (inductively coupled plasma MS) and UV/visible spectroscopy, Hpn was found to bind five Ni2+ ions per monomer at pH 7.4, with a dissociation constant (Kd) of 7.1 μM. Importantly, Ni2+ binding to Hpn is reversible: metal is released either in the presence of a chelating ligand such as EDTA, or at a slightly acidic pH (pH for half dissociation, pH1/2 ∼6.3). Ni2+ binding induces conformational changes within the protein, increasing β-sheet and reducing α-helical content, from 22% to 37%, and 20% to 10% respectively. Growth curves of Escherichia coli BL21(DE3) both with and without the hpn gene performed under Ni2+ pressure clearly implied a role for Hpn to protect the cells from higher concentrations of external metal ions. Similarly, the accumulation of Ni2+ in these cells expressing Hpn from a plasmid was approx. 4-fold higher than in uninduced controls or control cultures that lacked the plasmid. Similarly, levels of Ni2+ in wild-type H. pylori 26695 cells were higher than those in H. pylori hpn-deletion mutant strains. Hpn may potentially serve multiple roles inside the bacterium: storage of Ni 2+ ions in a 'reservoir'; donation of Ni2+ to other proteins; and detoxification via sequestration of excess Ni2+. © 2006 Biochemical Society. | en_HK |
dc.language | eng | en_HK |
dc.publisher | Portland Press Ltd. The Journal's web site is located at http://www.biochemj.org | en_HK |
dc.relation.ispartof | Biochemical Journal | en_HK |
dc.subject | Helicobacter pylori | en_HK |
dc.subject | Histidine-rich protein | en_HK |
dc.subject | Hpn | en_HK |
dc.subject | Nickel | en_HK |
dc.subject | Storage | en_HK |
dc.subject.mesh | Amino Acid Sequence | en_HK |
dc.subject.mesh | Bacterial Proteins - metabolism | en_HK |
dc.subject.mesh | Cloning, Molecular | en_HK |
dc.subject.mesh | Gene Expression Regulation, Bacterial | en_HK |
dc.subject.mesh | Helicobacter pylori - metabolism | en_HK |
dc.subject.mesh | Molecular Sequence Data | en_HK |
dc.subject.mesh | Nickel - metabolism | en_HK |
dc.subject.mesh | Protein Binding | en_HK |
dc.subject.mesh | Proteins - metabolism | en_HK |
dc.title | Expression and characterization of a histidine-rich protein, Hpn: Potential for Ni2+ storage in Helicobacter pylori | en_HK |
dc.type | Article | en_HK |
dc.identifier.email | Watt, RM:rmwatt@hku.hk | en_HK |
dc.identifier.email | Tanner, JA:jatanner@hku.hk | en_HK |
dc.identifier.email | Huang, JD:jdhuang@hkucc.hku.hk | en_HK |
dc.identifier.email | Sun, H:hsun@hkucc.hku.hk | en_HK |
dc.identifier.authority | Watt, RM=rp00043 | en_HK |
dc.identifier.authority | Tanner, JA=rp00495 | en_HK |
dc.identifier.authority | Huang, JD=rp00451 | en_HK |
dc.identifier.authority | Sun, H=rp00777 | en_HK |
dc.description.nature | link_to_OA_fulltext | - |
dc.identifier.doi | 10.1042/BJ20051160 | en_HK |
dc.identifier.pmid | 16164421 | - |
dc.identifier.pmcid | PMC1383687 | - |
dc.identifier.scopus | eid_2-s2.0-30044451654 | en_HK |
dc.identifier.hkuros | 113903 | en_HK |
dc.relation.references | http://www.scopus.com/mlt/select.url?eid=2-s2.0-30044451654&selection=ref&src=s&origin=recordpage | en_HK |
dc.identifier.volume | 393 | en_HK |
dc.identifier.issue | 1 | en_HK |
dc.identifier.spage | 285 | en_HK |
dc.identifier.epage | 293 | en_HK |
dc.identifier.isi | WOS:000234412400029 | - |
dc.publisher.place | United Kingdom | en_HK |
dc.identifier.f1000 | 1033680 | - |
dc.identifier.scopusauthorid | Ge, R=7005525090 | en_HK |
dc.identifier.scopusauthorid | Watt, RM=7102907536 | en_HK |
dc.identifier.scopusauthorid | Sun, X=8906547400 | en_HK |
dc.identifier.scopusauthorid | Tanner, JA=35513993000 | en_HK |
dc.identifier.scopusauthorid | He, QY=34770287900 | en_HK |
dc.identifier.scopusauthorid | Huang, JD=8108660600 | en_HK |
dc.identifier.scopusauthorid | Sun, H=7404827446 | en_HK |
dc.identifier.citeulike | 3814130 | - |
dc.identifier.issnl | 0264-6021 | - |