Recombinant Escherichia coli O157:H7 Zinc transport protein ZntB (zntB)
Description
Function and Transport Mechanism
ZntB is involved in zinc transport . Zinc is an essential microelement for sustaining life, but excess zinc is toxic; therefore, dedicated import, export, and storage proteins tightly regulate zinc concentration . ZntB mediates Zn2+ transport, which is stimulated by a pH gradient across the membrane . ZntB most likely mediates Zn2+/H+ co-transport, indicating it functions as a zinc importer . Studies show that the same fold within the CorA superfamily can be used either as a channel (CorA) or a transporter (ZntB) .
Structure
The full-length structure of the ZntB transporter is a member of the CorA MIT family . The protein encoded by the zntB locus is homologous to the CorA family of Mg 2+ transport proteins and is widely distributed among the eubacteria . Crystal structures are available of only cytoplasmic parts of ZntB .
Role in Zinc Homeostasis
ZntB is important for maintaining Zn2+ homeostasis in Enterobacteria . Several membrane transporters in Enterobacteriaceae are involved in zinc homeostasis and linked to virulence . ZntB helps regulate bacterial zinc concentrations and could be a target for new antimicrobial drugs, as zinc is critical to both human and pathogenic bacterial viability, and inhibiting zinc uptake could combat illness .
ZntB as a Zinc Efflux Pathway
The zntB locus of S. enterica serovar Typhimurium encodes a protein involved in the transmembrane flux of zinc . Mutations at zntB render the cell hypersensitive to the cytotoxic effects of zinc, suggesting ZntB plays a role in the efflux of this cation . ZntB mutations diminish the capacity to extrude Zn 2+ without significantly affecting the uptake activity . ZntB is not able to function as a Mg 2+ uptake pathway .
Research Findings
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ZntB mediates zinc uptake: Stimulated by a pH gradient across the membrane, using a transport mechanism that does not resemble the one proposed for homologous CorA channels .
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ZntB is a zinc importer: Driven by a proton gradient, with a transport mechanism distinct from that of CorA Mg2+ channels .
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ZntB affects the transport of Zn2+ and Cd2+: Analysis of regulation of ZntB expression in C. metallidurans revealed that it was downregulated in the presence of high concentrations of Zn2+, Cd2+, and Cu2+ .
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ZntB facilitates the efflux of zinc: Expression of ZntB from pAJW54 further increased the rate of 65Zn 2+ efflux .
Product Specs
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Target Background
Mediates the efflux of zinc ions.
KEGG: ecf:ECH74115_1990
