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Pathania, A. and Sardesai, A.A. (2015) Distinct paths for basic amino acid export in Escherichia coli: YbjE (LysO) mediates export of L-lysine. Journal of Bacteriology, 197 (12). pp. 2036-2047. ISSN 0021-9193

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Abstract

In Escherichia coli argO encodes an exporter for L-arginine (Arg) and its toxic analogue canavanine (CAN), and its transcriptional activation and repression, respectively by Arg and L-lysine (Lys) is mediated by the regulator ArgP. Accordingly argO and argP mutants are CAN supersensitive (CANSS). We report the identification of ybjE as a gene encoding a predicted inner membrane protein that mediates export of Lys and our results confirm the previous identification with a different approach of YbjE as a Lys exporter, reported in patent documents by Ueda and coworkers. ybjE was isolated as a multicopy suppressor of the CANSS phenotype of a strain lacking ArgO. Absence of YbjE did not confer a CANSS phenotype but instead conferred hypersensitivity to the lysine antimetabolite thialysine and led to growth inhibition by the dipeptide lysylalanine, the latter associated with elevated cellular Lys content. YbjE overproduction resulted in Lys excretion and syntrophic cross-feeding of a Lys auxotroph. Constitutive overexpression of argO promoted Lys cross-feeding that is indicative of a latent Lys export potential of ArgO. Arg modestly repressed ybjE transcription in an ArgR dependent manner and ArgR displayed Arg sensitive binding to the ybjE promoter region in vitro. Our studies suggest that the reciprocal repression of argO and ybjE respectively by Lys and Arg confers the specificity for basic amino acid export by distinct paths and that such cross-repression contributes to maintenance of cytoplasmic Arg/Lys balance. We propose that YbjE be re-designated as LysO.

Item Type: Article
Subjects: Molecular Biology
Depositing User: Dr P Divakar
Date Deposited: 16 May 2015 18:17
Last Modified: 03 Feb 2016 19:00
URI: http://cdfd.sciencecentral.in/id/eprint/34

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