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Article: Coordination of Zn2+ (and Cd2+) by prokaryotic metallothionein: Involvement of His-imidazole
Title | Coordination of Zn2+ (and Cd2+) by prokaryotic metallothionein: Involvement of His-imidazole |
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Authors | |
Issue Date | 1998 |
Publisher | American 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? |
Abstract | In 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 Identifier | http://hdl.handle.net/10722/167592 |
ISSN | 2020 Impact Factor: 5.157 2023 SCImago Journal Rankings: 1.766 |
ISI Accession Number ID | |
References |
DC Field | Value | Language |
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dc.contributor.author | Daniels, MJ | en_US |
dc.contributor.author | TurnerCavet, JS | en_US |
dc.contributor.author | Selkirk, R | en_US |
dc.contributor.author | Sun, H | en_US |
dc.contributor.author | Parkinson, JA | en_US |
dc.contributor.author | Sadler, PJ | en_US |
dc.contributor.author | Robinson, NJ | en_US |
dc.date.accessioned | 2012-10-08T03:08:52Z | - |
dc.date.available | 2012-10-08T03:08:52Z | - |
dc.date.issued | 1998 | en_US |
dc.identifier.citation | Journal Of Biological Chemistry, 1998, v. 273 n. 36, p. 22957-22961 | en_US |
dc.identifier.issn | 0021-9258 | en_US |
dc.identifier.uri | http://hdl.handle.net/10722/167592 | - |
dc.description.abstract | In 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.language | eng | en_US |
dc.publisher | American Society for Biochemistry and Molecular Biology, Inc. The Journal's web site is located at http://www.jbc.org/ | en_US |
dc.relation.ispartof | Journal of Biological Chemistry | en_US |
dc.title | Coordination of Zn2+ (and Cd2+) by prokaryotic metallothionein: Involvement of His-imidazole | en_US |
dc.type | Article | en_US |
dc.identifier.email | Sun, H:hsun@hkucc.hku.hk | en_US |
dc.identifier.authority | Sun, H=rp00777 | en_US |
dc.description.nature | link_to_subscribed_fulltext | en_US |
dc.identifier.doi | 10.1074/jbc.273.36.22957 | en_US |
dc.identifier.pmid | 9722517 | - |
dc.identifier.scopus | eid_2-s2.0-0032483170 | en_US |
dc.relation.references | http://www.scopus.com/mlt/select.url?eid=2-s2.0-0032483170&selection=ref&src=s&origin=recordpage | en_US |
dc.identifier.volume | 273 | en_US |
dc.identifier.issue | 36 | en_US |
dc.identifier.spage | 22957 | en_US |
dc.identifier.epage | 22961 | en_US |
dc.identifier.isi | WOS:000075778100017 | - |
dc.publisher.place | United States | en_US |
dc.identifier.scopusauthorid | Daniels, MJ=19634347900 | en_US |
dc.identifier.scopusauthorid | TurnerCavet, JS=7801492350 | en_US |
dc.identifier.scopusauthorid | Selkirk, R=6507602287 | en_US |
dc.identifier.scopusauthorid | Sun, H=7404827446 | en_US |
dc.identifier.scopusauthorid | Parkinson, JA=54402144900 | en_US |
dc.identifier.scopusauthorid | Sadler, PJ=7103024488 | en_US |
dc.identifier.scopusauthorid | Robinson, NJ=7201402446 | en_US |
dc.identifier.issnl | 0021-9258 | - |