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Expression of the PitA phosphate/metal transporter of Escherichia coli is responsive to zinc and inorganic phosphate levels

Lookup NU author(s): Dr Richard Jackson, Dr Alison Graham

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Abstract

Escherichia coli possesses two major systems for inorganic phosphate (P(i)) uptake. The Pst system (pstSCAB) is inducible by low phosphate concentrations whereas the low-affinity transporter (pitA) has been described as constitutively expressed. PitA catalyses transport of metal [Mg(II), Ca(II)]-phosphate complexes, and mutations in pitA confer Zn(II) resistance. Here we report that pitA transcription is not constitutive; activity of a single-copy pitA-lacZ transcriptional fusion (monolysogen) was maximal at high extracellular Zn(II) (150 mu M), in the absence of added P(i), and in a well-defined pitA mutant strain. Intracellular zinc levels were unaffected by adding Zn(II) to the medium for both the wild-type and mutant strains. However, in the wild-type strain, Mg levels (per gram of dry biomass) fell by eightfold in cells grown with added Zn(II) and by 20-fold when Zn(II) and P(i) were added to cultures. Mutation of pitA reduced the effects of external Zn(II) and phosphate levels on Mg pools, consistent with competition or inhibition by Zn(II) of PitA. The mechanism of pitA regulation by extracellular Zn(II) and P(i) is unknown but appears not to involve Fur or other well-characterized regulators.


Publication metadata

Author(s): Jackson RJ, Binet MRB, Lee LJ, Ma R, Graham AI, McLeod CW, Poole RK

Publication type: Article

Journal: FEMS Microbiology Letters

Year: 2008

Volume: 289

Issue: 2

Pages: 219-224

ISSN (print): 0378-1097

ISSN (electronic): 1574-6968

Publisher: Wiley-Blackwell Publishing Ltd.

URL: http://dx.doi.org/10.1111/j.1574-6968.2008.01386.x

DOI: 10.1111/j.1574-6968.2008.01386.x


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