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Article: Expression and characterization of a histidine-rich protein, Hpn: Potential for Ni2+ storage in Helicobacter pylori

TitleExpression and characterization of a histidine-rich protein, Hpn: Potential for Ni2+ storage in Helicobacter pylori
Authors
KeywordsHelicobacter pylori
Histidine-rich protein
Hpn
Nickel
Storage
Issue Date2006
PublisherPortland 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?
AbstractHpn 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 Identifierhttp://hdl.handle.net/10722/68093
ISSN
2015 Impact Factor: 3.562
2015 SCImago Journal Rankings: 2.582
PubMed Central ID
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorGe, Ren_HK
dc.contributor.authorWatt, RMen_HK
dc.contributor.authorSun, Xen_HK
dc.contributor.authorTanner, JAen_HK
dc.contributor.authorHe, QYen_HK
dc.contributor.authorHuang, JDen_HK
dc.contributor.authorSun, Hen_HK
dc.date.accessioned2010-09-06T06:01:16Z-
dc.date.available2010-09-06T06:01:16Z-
dc.date.issued2006en_HK
dc.identifier.citationBiochemical Journal, 2006, v. 393 n. 1, p. 285-293en_HK
dc.identifier.issn0264-6021en_HK
dc.identifier.urihttp://hdl.handle.net/10722/68093-
dc.description.abstractHpn 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.languageengen_HK
dc.publisherPortland Press Ltd. The Journal's web site is located at http://www.biochemj.orgen_HK
dc.relation.ispartofBiochemical Journalen_HK
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.subjectHelicobacter pylorien_HK
dc.subjectHistidine-rich proteinen_HK
dc.subjectHpnen_HK
dc.subjectNickelen_HK
dc.subjectStorageen_HK
dc.subject.meshAmino Acid Sequenceen_HK
dc.subject.meshBacterial Proteins - metabolismen_HK
dc.subject.meshCloning, Molecularen_HK
dc.subject.meshGene Expression Regulation, Bacterialen_HK
dc.subject.meshHelicobacter pylori - metabolismen_HK
dc.subject.meshMolecular Sequence Dataen_HK
dc.subject.meshNickel - metabolismen_HK
dc.subject.meshProtein Bindingen_HK
dc.subject.meshProteins - metabolismen_HK
dc.titleExpression and characterization of a histidine-rich protein, Hpn: Potential for Ni2+ storage in Helicobacter pylorien_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0264-6021&volume=393&spage=285&epage=293&date=2006&atitle=Expression+and+characterization+of+a+histidine-rich+protein,+Hpn:+potential+for+Ni2++storage+in+Helicobacter+pylorien_HK
dc.identifier.emailWatt, RM:rmwatt@hku.hken_HK
dc.identifier.emailTanner, JA:jatanner@hku.hken_HK
dc.identifier.emailHuang, JD:jdhuang@hkucc.hku.hken_HK
dc.identifier.emailSun, H:hsun@hkucc.hku.hken_HK
dc.identifier.authorityWatt, RM=rp00043en_HK
dc.identifier.authorityTanner, JA=rp00495en_HK
dc.identifier.authorityHuang, JD=rp00451en_HK
dc.identifier.authoritySun, H=rp00777en_HK
dc.description.naturepublished_or_final_version-
dc.identifier.doi10.1042/BJ20051160en_HK
dc.identifier.pmid16164421-
dc.identifier.pmcidPMC1383687-
dc.identifier.scopuseid_2-s2.0-30044451654en_HK
dc.identifier.hkuros113903en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-30044451654&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume393en_HK
dc.identifier.issue1en_HK
dc.identifier.spage285en_HK
dc.identifier.epage293en_HK
dc.identifier.isiWOS:000234412400029-
dc.publisher.placeUnited Kingdomen_HK
dc.identifier.f10001033680-
dc.identifier.scopusauthoridGe, R=7005525090en_HK
dc.identifier.scopusauthoridWatt, RM=7102907536en_HK
dc.identifier.scopusauthoridSun, X=8906547400en_HK
dc.identifier.scopusauthoridTanner, JA=35513993000en_HK
dc.identifier.scopusauthoridHe, QY=34770287900en_HK
dc.identifier.scopusauthoridHuang, JD=8108660600en_HK
dc.identifier.scopusauthoridSun, H=7404827446en_HK
dc.identifier.citeulike3814130-

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