An E. coli gene emrD is involved in adaptation to low energy shock.

E. coli adapt to uncouplers in the presence of a non-fermentable carbon source. Adaptation is accompanied by the restoration of the proton motive force and ATP. A collection of uncoupler-sensitive Tn,lacZ,kan fusion strains was obtained by ampicillin enrichment in the presence of TSA. One of the fusion strains was induced by uncouplers. The fusion gene emrD was mapped to min. 83.1, cloned and sequenced. EmrD is a member of the major facilitator family of pmf-dependent translocases and is homologous to a number of bacterial multidrug resistance pumps. Resistance to some uncouplers including TTFB was not affected by emrD, and growth recovery to this uncoupler was very sluggish. It is suggested that EmrD is a new bacterial multidrug resistance pump that participates in a low energy shock adaptive response.