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Journal of Bacteriology, June 2004, p. 3539-3546, Vol. 186, No. 11
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.11.3539-3546.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Evidence for an Arginine Exporter Encoded by yggA (argO) That Is Regulated by the LysR-Type Transcriptional Regulator ArgP in Escherichia coli

Madhusudan R. Nandineni1,2 and J. Gowrishankar2*

Centre for Cellular and Molecular Biology, Hyderabad 500007,1 Laboratory of Bacterial Genetics, Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500076, India2

Received 9 November 2003/ Accepted 19 February 2004

The anonymous open reading frame yggA of Escherichia coli was identified in this study as a gene that is under the transcriptional control of argP (previously called iciA), which encodes a LysR-type transcriptional regulator protein. Strains with null mutations in either yggA or argP were supersensitive to the arginine analog canavanine, and yggA-lac expression in vivo exhibited argP+-dependent induction by arginine. Lysine supplementation phenocopied the argP null mutation in that it virtually abolished yggA expression, even in the argP+ strain. The dipeptides arginylalanine and lysylalanine behaved much like arginine and lysine, respectively, to induce and to turn off yggA transcription. Dominant missense mutations in argP (argPd) that conferred canavanine resistance and rendered yggA-lac expression constitutive were obtained. The protein deduced to be encoded by yggA shares similarity with a basic amino acid exporter (LysE) of Corynebacterium glutamicum, and we obtained evidence for increased arginine efflux from E. coli strains with either the argPd mutation or multicopy yggA+. The null yggA mutation abolished the increased arginine efflux from the argPd strain. Our results suggest that yggA encodes an ArgP-regulated arginine exporter, and we have accordingly renamed it argO (for "arginine outward transport"). We propose that the physiological function of argO may be either to prevent the accumulation to toxic levels of canavanine (which is a plant-derived antimetabolite) or arginine or to maintain an appropriate balance between the intracellular lysine and arginine concentrations.


* Corresponding author. Mailing address: Laboratory of Bacterial Genetics, Centre for DNA Fingerprinting and Diagnostics, ECIL Rd., Nacharam, Hyderabad 500 076, India, Phone: 91-40-27155609. Fax: 91-40-27155610. E-mail: shankar{at}cdfd.org.in.


Journal of Bacteriology, June 2004, p. 3539-3546, Vol. 186, No. 11
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.11.3539-3546.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.




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