Members of the Conserved DedA Family Are Likely Membrane Transporters and Are Required for Drug Resistance in Escherichia coli

Abstract

ABSTRACTBacterial resistance to antibiotics and biocides is an increasing public health problem. Genes encoding integral membrane proteins belonging to the DedA family are present in most bacterial genomes, includingEscherichia coli. AnE. colistrain lacking partially redundant DedA family genesyqjAandyghB(strain BC202) displays temperature sensitivity and cell division defects. These phenotypes can be corrected by overexpression ofmdfA, an Na+-K+/H+antiporter of the major facilitator superfamily. We show that BC202 is hypersensitive to several biocides and cationic compounds that are known substrates of several multidrug resistance transporters, including MdfA, EmrE, and AcrB. The introduction of deletions of genes encoding these drug transporters into BC202 results in additional sensitivity. Expression of wild-typeyghBoryqjAcan restore drug resistance, but this is eliminated upon mutation of two membrane-embedded acidic amino acids (E39 or D51 in either protein). This dependence upon membrane-embedded acidic amino acids is a hallmark of proton-dependent antiporters. Overexpression ofmdfAin BC202 or artificially restoring proton motive force (PMF) restores wild-type resistance to substrates of MdfA as well as other drug resistance transporters such as EmrE and AcrAB. These results suggest that YqjA and YghB may be membrane transporters required for PMF-dependent drug efflux inE. coli.