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Article: Coordination of Zn2+ (and Cd2+) by prokaryotic metallothionein: Involvement of His-imidazole

TitleCoordination of Zn2+ (and Cd2+) by prokaryotic metallothionein: Involvement of His-imidazole
Authors
Issue Date1998
PublisherAmerican Society for Biochemistry and Molecular Biology, Inc. The Journal's web site is located at http://www.jbc.org/
Citation
Journal Of Biological Chemistry, 1998, v. 273 n. 36, p. 22957-22961 How to Cite?
AbstractIn mammalian metallothionein Zn 2+ is exclusively coordinated to Cys- thiolate to form clusters in which the metal is thermodynamically stable but also kinetically labile. By contrast, little is known about coordination to prokaryotic metallothionein, SmtA. 3 nmol of Zn 2+ nmol -1 SmtA were displaced by 8 nmol of p-(hydroxymercuri)phenylsulfonate implicating eight of the nine Cys in the coordination of three metal ions. None of the Zn 2+ associated with SmtA was accessible to 4-(2-pyridylazo)resorcinol prior to the addition of p-(hydroxymercuri)phenylsulfonate. An unusual feature of SmtA is the presence of three His residues, and we have investigated whether these contribute to metal coordination. Less Zn 2+ was associated with purified SmtA(H40R/H49R/H55R), in which all three His residues were substituted with Arg, and approximately one equivalent of Zn 2+ was immediately accessible to 4-(2-pyridylazo)resorcinol. Following incubation of SmtA with 111Cd, three 111Cd resonances were detected, two in a range expected for CdS 4 and the third indicative of either CdNS 3 or CdN 2S 2 coordination. Two-dimensional TOCSY 1H NMR and 111Cd-edited 1H NMR showed two His residues bound to 111Cd, confirming CdN 2S 2 coordination. The pH of half-dissociation of Zn 2+ increased from 4.05 for SmtA to 5.37 for SmtA(H40R/H49R/H55R). Equivalent values for single His mutants SmtA(H40R), SmtA(H49R), and SmtA(H55R) were 4.62, 4.48, and 3.81, respectively, revealing that conversion of His 40 or His 49 to Arg impairs Zn 2+ binding at the CdN 2S 2 and CdS 4 sites. Only approximately two equivalents of Zn 2+ were associated with purified SmtA(H49R). The appearance of a fourth 111Cd resonance at lower pH suggests that an alternative CdN 2S 2 site also exists.
Persistent Identifierhttp://hdl.handle.net/10722/167592
ISSN
2015 Impact Factor: 4.258
2015 SCImago Journal Rankings: 3.151
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorDaniels, MJen_US
dc.contributor.authorTurnerCavet, JSen_US
dc.contributor.authorSelkirk, Ren_US
dc.contributor.authorSun, Hen_US
dc.contributor.authorParkinson, JAen_US
dc.contributor.authorSadler, PJen_US
dc.contributor.authorRobinson, NJen_US
dc.date.accessioned2012-10-08T03:08:52Z-
dc.date.available2012-10-08T03:08:52Z-
dc.date.issued1998en_US
dc.identifier.citationJournal Of Biological Chemistry, 1998, v. 273 n. 36, p. 22957-22961en_US
dc.identifier.issn0021-9258en_US
dc.identifier.urihttp://hdl.handle.net/10722/167592-
dc.description.abstractIn mammalian metallothionein Zn 2+ is exclusively coordinated to Cys- thiolate to form clusters in which the metal is thermodynamically stable but also kinetically labile. By contrast, little is known about coordination to prokaryotic metallothionein, SmtA. 3 nmol of Zn 2+ nmol -1 SmtA were displaced by 8 nmol of p-(hydroxymercuri)phenylsulfonate implicating eight of the nine Cys in the coordination of three metal ions. None of the Zn 2+ associated with SmtA was accessible to 4-(2-pyridylazo)resorcinol prior to the addition of p-(hydroxymercuri)phenylsulfonate. An unusual feature of SmtA is the presence of three His residues, and we have investigated whether these contribute to metal coordination. Less Zn 2+ was associated with purified SmtA(H40R/H49R/H55R), in which all three His residues were substituted with Arg, and approximately one equivalent of Zn 2+ was immediately accessible to 4-(2-pyridylazo)resorcinol. Following incubation of SmtA with 111Cd, three 111Cd resonances were detected, two in a range expected for CdS 4 and the third indicative of either CdNS 3 or CdN 2S 2 coordination. Two-dimensional TOCSY 1H NMR and 111Cd-edited 1H NMR showed two His residues bound to 111Cd, confirming CdN 2S 2 coordination. The pH of half-dissociation of Zn 2+ increased from 4.05 for SmtA to 5.37 for SmtA(H40R/H49R/H55R). Equivalent values for single His mutants SmtA(H40R), SmtA(H49R), and SmtA(H55R) were 4.62, 4.48, and 3.81, respectively, revealing that conversion of His 40 or His 49 to Arg impairs Zn 2+ binding at the CdN 2S 2 and CdS 4 sites. Only approximately two equivalents of Zn 2+ were associated with purified SmtA(H49R). The appearance of a fourth 111Cd resonance at lower pH suggests that an alternative CdN 2S 2 site also exists.en_US
dc.languageengen_US
dc.publisherAmerican Society for Biochemistry and Molecular Biology, Inc. The Journal's web site is located at http://www.jbc.org/en_US
dc.relation.ispartofJournal of Biological Chemistryen_US
dc.titleCoordination of Zn2+ (and Cd2+) by prokaryotic metallothionein: Involvement of His-imidazoleen_US
dc.typeArticleen_US
dc.identifier.emailSun, H:hsun@hkucc.hku.hken_US
dc.identifier.authoritySun, H=rp00777en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1074/jbc.273.36.22957en_US
dc.identifier.pmid9722517-
dc.identifier.scopuseid_2-s2.0-0032483170en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-0032483170&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume273en_US
dc.identifier.issue36en_US
dc.identifier.spage22957en_US
dc.identifier.epage22961en_US
dc.identifier.isiWOS:000075778100017-
dc.publisher.placeUnited Statesen_US
dc.identifier.scopusauthoridDaniels, MJ=19634347900en_US
dc.identifier.scopusauthoridTurnerCavet, JS=7801492350en_US
dc.identifier.scopusauthoridSelkirk, R=6507602287en_US
dc.identifier.scopusauthoridSun, H=7404827446en_US
dc.identifier.scopusauthoridParkinson, JA=54402144900en_US
dc.identifier.scopusauthoridSadler, PJ=7103024488en_US
dc.identifier.scopusauthoridRobinson, NJ=7201402446en_US

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