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Antimicrobial Agents and Chemotherapy, July 2005, p. 2965-2971, Vol. 49, No. 7
0066-4804/05/$08.00+0     doi:10.1128/AAC.49.7.2965-2971.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Structural and Functional Study of the Phenicol-Specific Efflux Pump FloR Belonging to the Major Facilitator Superfamily

Martine Braibant,1 Jacqueline Chevalier,2 Elisabeth Chaslus-Dancla,1 Jean-Marie Pagès,2 and Axel Cloeckaert1*

UR86 Bio-Agresseurs, Santé, Environnement, Institut National de la Recherche Agronomique, Centre de Recherche de Tours, 37380 Nouzilly,1 EA2197, IFR48, Faculté de Médecine, Université de la Méditerranée, 13385 Marseille Cedex 05, France2

Received 5 January 2005/ Returned for modification 15 March 2005/ Accepted 5 April 2005

The florfenicol-chloramphenicol resistance gene floR from Salmonella enterica was previously identified and postulated to belong to the major facilitator (MF) superfamily of drug exporters. Here, we confirmed a computer-predicted transmembrane topological model of FloR, using the phoA gene fusion method, and classified this protein in the DHA12 family (containing 12 transmembrane domains) of MF efflux transporters. We also showed that FloR is a transporter specific for structurally associated phenicol drugs (chloramphenicol, florfenicol, thiamphenicol) which utilizes the proton motive force to energize an active efflux mechanism. By site-directed mutagenesis of specific charged residues belonging to putative transmembrane segments (TMS), two residues essential for active efflux function, D23 in TMS1 and R109 in TMS4, were identified. Of these, the acidic residue D23 seems to participate directly in the affinity pocket involved in phenicol derivative recognition. A third residue, E283 in TMS9, seems to be necessary for correct membrane folding of the transporter.

* Corresponding author. Mailing address: UR86 Bio-Agresseurs, Santé, Environnement, Institut National de la Recherche Agronomique, Centre de Recherche de Tours, 37380 Nouzilly, France. Phone: 02 47 42 77 50. Fax: 02 47 42 77 74. E-mail: cloeckae{at}tours.inra.fr.

Antimicrobial Agents and Chemotherapy, July 2005, p. 2965-2971, Vol. 49, No. 7
0066-4804/05/$08.00+0     doi:10.1128/AAC.49.7.2965-2971.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Vecchione, J. J., Alexander, B. Jr., Sello, J. K. (2009). Two Distinct Major Facilitator Superfamily Drug Efflux Pumps Mediate Chloramphenicol Resistance in Streptomyces coelicolor. Antimicrob. Agents Chemother. 53: 4673-4677 [Abstract] [Full Text]  
  • Kehrenberg, C., Meunier, D., Targant, H., Cloeckaert, A., Schwarz, S., Madec, J.-Y. (2006). Plasmid-mediated florfenicol resistance in Pasteurella trehalosi. J Antimicrob Chemother 58: 13-17 [Abstract] [Full Text]  
  • Yin, Y., He, X., Szewczyk, P., Nguyen, T., Chang, G. (2006). Structure of the Multidrug Transporter EmrD from Escherichia coli. Science 312: 741-744 [Abstract] [Full Text]  


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