Coordination of Zn2+ (and Cd2+) by Prokaryotic Metallothionein

Daniels, Michael J.; Cavet, James; Selkirk, Richard; Sun, Hongzhe; Parkinson, John A.; Sadler, Peter J.; Robinson, Nigel J.

doi:10.1074/jbc.273.36.22957

Cited by 71 publications

(51 citation statements)

References 31 publications

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“…There are five histidine motifs in the PhpA protein that occur in hydrophilic areas of the molecule and may be involved in its biological function. Histidine motifs have been shown to be important in divalent cation binding and specifically in the binding of zinc ions (7,23) unknown, as are the size and location of the mature protein in S. pneumoniae. Polyclonal antisera generated in mice selectively bound to a single protein of the largest predicted size (i.e., 94 kDa) in four of the six whole-cell lysates examined, while several bands in the 80-to 95-kDa size range in culture supernatants of all six of the serotypes examined reacted with the antisera (Fig.…”

Section: Discussionmentioning

confidence: 99%

Recombinant PhpA Protein, a Unique Histidine Motif-Containing Protein fromStreptococcus pneumoniae, Protects Mice against Intranasal Pneumococcal Challenge

et al. 2001

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The multivalent pneumococcal conjugate vaccine is effective against both systemic disease and otitis media caused by serotypes contained in the vaccine. However, serotypes not covered by the current conjugate vaccine may still cause pneumococcal disease. To address these serotypes and the remaining otitis media due to Streptococcus pneumoniae, we have been evaluating antigenically conserved proteins from S. pneumoniae as vaccine candidates. A previous report identified a 20-kDa protein with putative human complement C3-proteolytic activity. By utilizing the publicly released pneumococcal genomic sequences, we found the gene encoding the 20-kDa protein to be part of a putative open reading frame of approximately 2,400 bp. We recombinantly expressed a 79-kDa fragment (rPhpA-79) that contains a repeated HxxHxH motif and evaluated it for vaccine potential. The antibodies elicited by the purified rPhpA-79 protein were cross-reactive to proteins from multiple strains of S. pneumoniae and were against surface-exposed epitopes. Immunization with rPhpA-79 protein adjuvanted with monophosphoryl lipid A (for subcutaneous immunization) or a mutant cholera toxin, CT-E29H (for intranasal immunization), protected CBA/N mice against death and bacteremia, as well as reduced nasopharyngeal colonization, following intranasal challenge with a heterologous pneumococcal strain. In contrast, immunization with the 20-kDa portion of the PhpA protein did not protect mice. These results suggest that rPhpA-79 is a potential candidate for use as a vaccine against pneumococcal systemic disease and otitis media.

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Section: Discussionmentioning

confidence: 99%

Recombinant PhpA Protein, a Unique Histidine Motif-Containing Protein fromStreptococcus pneumoniae, Protects Mice against Intranasal Pneumococcal Challenge

et al. 2001

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“…To express SmtA in E. coli, an NdeI restriction site was introduced at the 5Ј end of the SmtA coding region in pMDNR1.1 (14) by using Quik-change mutagenesis (Stratagene). The resulting NdeI͞BamHI fragment was subcloned into pET29a (Novagen), creating pMHNR1.1.…”

Section: Methodsmentioning

confidence: 99%

“…SmtA contains a smaller proportion of Cys than mammalian MT (16% vs. 33% of residues), and, unlike mammalian MTs, contains His residues, which have been implicated in metal coordination (14). The Cys coordination pattern for the MT clusters cannot be mapped onto the sequence of SmtA.…”

mentioning

confidence: 99%

A metallothionein containing a zinc finger within a four-metal cluster protects a bacterium from zinc toxicity

Blindauer

Harrison

Parkinson

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

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172

183

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Zinc is essential for many cellular processes, including DNA synthesis, transcription, and translation, but excess can be toxic. A zinc-induced gene, smtA, is required for normal zinc-tolerance in the cyanobacterium Synechococcus PCC 7942. Here we report that the protein SmtA contains a cleft lined with Cys-sulfur and His-imidazole ligands that binds four zinc ions in a Zn4Cys9His2 cluster. The thiolate sulfurs of five Cys ligands provide bridges between the two ZnCys 4 and two ZnCys3His sites, giving two fused six-membered rings with distorted boat conformations. The inorganic core strongly resembles the Zn4Cys11 cluster of mammalian metallothionein, despite different amino acid sequences, a different linear order of the ligands, and presence of histidine ligands. Also, SmtA contains elements of secondary structure not found in metallothioneins. One of the two Cys4-coordinated zinc ions in SmtA readily exchanges with exogenous metal ( 111 Cd), whereas the other is inert. The thiolate sulfur ligands bound to zinc in this site are buried within the protein.Regions of ␤-strand and ␣-helix surround the inert site to form a zinc finger resembling the zinc fingers in GATA and LIM-domain proteins. Eukaryotic zinc fingers interact specifically with other proteins or DNA and an analogous interaction can therefore be anticipated for prokaryotic zinc fingers. SmtA now provides structural proof for the existence of zinc fingers in prokaryotes, and sequences related to the zinc finger motif can be identified in several bacterial genomes.

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“…15,16) The transcript of type 3 MT-like proteins has been found in leaves, fruits and developing embryos, 17,18) while the transcript of Ec type has been found to be restricted to plant reproductive organs. [19][20][21] To date, only a limited number of plant Ec type MT-like genes have been isolated and characterized in detail. 20,21) An SiMT gene encoding an Ec type of MT-like protein in sesame seeds was cloned in this study, and its tissuespecific expression characterized.…”

Section: -3)mentioning

confidence: 99%

“…[19][20][21] To date, only a limited number of plant Ec type MT-like genes have been isolated and characterized in detail. 20,21) An SiMT gene encoding an Ec type of MT-like protein in sesame seeds was cloned in this study, and its tissuespecific expression characterized. A recombinant GSTSiMT fusion protein was over-expressed in Escherichia coli, and its capability for binding to metal ions was examined.…”

Section: -3)mentioning

confidence: 99%

Cloning and Expression of a Seed-Specific Metallothionein-Like Protein from Sesame

Chyan

Lee

Liu

et al. 2005

Bioscience, Biotechnology, and Biochemistry

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Coordination of Zn2+ (and Cd2+) by Prokaryotic Metallothionein

Cited by 71 publications

References 31 publications

Recombinant PhpA Protein, a Unique Histidine Motif-Containing Protein fromStreptococcus pneumoniae, Protects Mice against Intranasal Pneumococcal Challenge

Recombinant PhpA Protein, a Unique Histidine Motif-Containing Protein fromStreptococcus pneumoniae, Protects Mice against Intranasal Pneumococcal Challenge

A metallothionein containing a zinc finger within a four-metal cluster protects a bacterium from zinc toxicity

Cloning and Expression of a Seed-Specific Metallothionein-Like Protein from Sesame

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