Characterization of the l-alanine exporter AlaE of Escherichia coli and its potential role in protecting cells from a toxic-level accumulation of l-alanine and its derivatives.

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  • Additional Information
    • Source:
      Publisher: Wiley-Blackwell Country of Publication: England NLM ID: 101588314 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 2045-8827 (Electronic) Linking ISSN: 20458827 NLM ISO Abbreviation: Microbiologyopen Subsets: MEDLINE
    • Publication Information:
      Original Publication: Oxford : Wiley-Blackwell
    • Subject Terms:
      Alanine/*metabolism ; Alanine/*toxicity ; Amino Acid Transport Systems, Neutral/*metabolism ; Escherichia coli/*metabolism ; Escherichia coli Proteins/*metabolism; Amino Acid Transport Systems, Neutral/deficiency ; Biological Transport ; Dipeptides/metabolism ; Dipeptides/toxicity ; Escherichia coli/genetics ; Escherichia coli/growth & development ; Gene Deletion ; Genetic Complementation Test ; Microbial Sensitivity Tests ; Plasmids ; Proton-Motive Force
    • Abstract:
      We previously reported that the alaE gene of Escherichia coli encodes the l-alanine exporter AlaE. The objective of this study was to elucidate the mechanism of the AlaE exporter. The minimum inhibitory concentration of l-alanine and l-alanyl-l-alanine in alaE-deficient l-alanine-nonmetabolizing cells MLA301ΔalaE was 4- and >4000-fold lower, respectively, than in the alaE-positive parent cells MLA301, suggesting that AlaE functions as an efflux pump to avoid a toxic-level accumulation of intracellular l-alanine and its derivatives. Furthermore, the growth of the alaE-deficient mutant derived from the l-alanine-metabolizing strain was strongly inhibited in the presence of a physiological level of l-alanyl-l-alanine. Intact MLA301ΔalaE and MLA301ΔalaE/pAlaE cells producing plasmid-borne AlaE, accumulated approximately 200% and 50%, respectively, of the [(3) H]l-alanine detected in MLA301 cells, suggesting that AlaE exports l-alanine. When 200 mmol/L l-alanine-loaded inverted membrane vesicles prepared from MLA301ΔalaE/pAlaE were placed in a solution containing 200 mmol/L or 0.34 μmol/L l-alanine, energy-dependent [(3) H]l-alanine accumulation occurred under either condition. This energy-dependent uphill accumulation of [(3) H]l-alanine was strongly inhibited in the presence of carbonyl cyanide m-chlorophenylhydrazone but not by dicyclohexylcarbodiimide, suggesting that the AlaE-mediated l-alanine extrusion was driven by proton motive force. Based on these results, physiological roles of the l-alanine exporter are discussed.
      (© 2015 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.)
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    • Contributed Indexing:
      Keywords: Escherichia coli; exporter; l-alanine
    • Accession Number:
      0 (AlaE protein, E coli)
      0 (Amino Acid Transport Systems, Neutral)
      0 (Dipeptides)
      0 (Escherichia coli Proteins)
      2867-20-1 (alanylalanine)
      OF5P57N2ZX (Alanine)
    • Publication Date:
      Date Created: 20150616 Date Completed: 20160502 Latest Revision: 20181113
    • Publication Date:
      20221213
    • Accession Number:
      PMC4554458
    • Accession Number:
      10.1002/mbo3.269
    • Accession Number:
      26073055