Multiple metal binding domains enhance the Zn(II) selectivity of the divalent metal ion transporter AztA

Tong Liu, Hermes Reyes-Caballero, Chenxi Li, Robert A. Scott, David P. Giedroc

Research output: Contribution to journalArticle

Abstract

Transition metal-transporting P1B-type CPx ATPases play crucial roles in mediating metal homeostasis and resistance in all cells. The degree to which N-terminal metal binding domains (MBDs) confer metal specificity to the transporter is unclear. We show that the two MBDs of the Zn/Cd/Pb effluxing pump Anabaena AztA are functionally nonequivalent, but only with respect to zinc resistance. Inactivation of the a-MBD largely abrogates resistance to high intracellular Zn(II) levels, whereas inactivation of the b-MBD is not as deleterious. In contrast, inactivation of either the a- or b-MBD has little measurable impact on Cd(II) and Pb(II) resistance. The membrane proximal b-MBD binds Zn(II) with a higher affinity than the distal N-terminal a-MBD. Facile Zn(II)-specific intermolecular transfer from the a-MBD to the higher-affinity b-MBD is readily observed by 1H-15N HSQC spectroscopy. Unlike Zn(II), Cd(II) and Pb(II) form saturated 1:1 S4 or S 3(O/N) complexes with AztAaHbH, where a single metal ion bridges the two MBDs. We propose that the tandem MBDs enhance Zn(II)-specific transport, while stabilizing a non-native inter-MBD Cd/Pb cross-linked structure that is a poor substrate and/or regulator for the transporter.

Original languageEnglish (US)
Pages (from-to)11057-11068
Number of pages12
JournalBiochemistry
Volume46
Issue number39
DOIs
StatePublished - Oct 2 2007
Externally publishedYes

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Metal ions
Metals
Ions
Anabaena
Transition metals
Adenosine Triphosphatases
Zinc
Spectrum Analysis
Pumps
Spectroscopy
Homeostasis
Membranes

ASJC Scopus subject areas

  • Biochemistry

Cite this

Multiple metal binding domains enhance the Zn(II) selectivity of the divalent metal ion transporter AztA. / Liu, Tong; Reyes-Caballero, Hermes; Li, Chenxi; Scott, Robert A.; Giedroc, David P.

In: Biochemistry, Vol. 46, No. 39, 02.10.2007, p. 11057-11068.

Research output: Contribution to journalArticle

Liu, Tong ; Reyes-Caballero, Hermes ; Li, Chenxi ; Scott, Robert A. ; Giedroc, David P. / Multiple metal binding domains enhance the Zn(II) selectivity of the divalent metal ion transporter AztA. In: Biochemistry. 2007 ; Vol. 46, No. 39. pp. 11057-11068.
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