NorM, a Putative Multidrug Efflux Protein, of Vibrio parahaemolyticus and Its Homolog in Escherichia coli

Abstract

We found that cells of Vibrio parahaemolyticus possess an energy-dependent efflux system for norfloxacin. We cloned a gene for a putative norfloxacin efflux protein from the chromosomal DNA ofV. parahaemolyticus by using an Escherichia coli mutant lacking the major multidrug efflux system AcrAB as the host and sequenced the gene (norM). Cells of E. coli transformed with a plasmid carrying the norMgene showed elevated energy-dependent efflux of norfloxacin. The transformants showed elevated resistance not only to norfloxacin and ciprofloxacin but also to the structurally unrelated compounds ethidium, kanamycin, and streptomycin. These results suggest that this is a multidrug efflux system. The hydropathy pattern of the deduced amino acid sequence of NorM suggested the presence of 12 transmembrane domains. The deduced primary structure of NorM showed 57% identity and 88% similarity with that of a hypothetical E. coli membrane protein, YdhE. No reported drug efflux protein in the sequence databases showed significant sequence similarity with NorM. Thus, NorM seems to be a novel type of multidrug efflux protein. We cloned the ydhE gene from E. coli. Cells ofE. coli transformed with the cloned ydhE gene showed elevated resistance to norfloxacin, ciprofloxacin, acriflavine, and tetraphenylphosphonium ion, but not to ethidium, when MICs were measured. Thus, it seems that NorM and YdhE differ somehow in substrate specificity.

MATE1 has an external COOH terminus, consistent with a 13-helix topology

“…The prototypic member of the MATE family of transport proteins is the prokaryotic OC/Na exchanger, NorM (14). By several different hydropathy algorithms, NorM appears to have 12 TMHs, although this has not been verified experimentally.…”

Emergence of resistance to antibacterial agents: the role of quaternary ammonium compounds—a critical review

“…These genes were plasmid-encoded with resistance attributable to plasmid acquisition. Escherichia coli biocide transporters included the AcrAB efflux pump (RND) [46,47], the EmrE pump (SMR) [48], the YdhE (MATE) protein [49], the MdfA (MATE) protein [50] and the TehA protein (MFS) [51]. Upregulation of AcrAB efflux pump expression is mostly under the control of the multiple antibiotic resistance activator (MarA).…”

Secondary transport as an efficient membrane transport mechanism for plant secondary metabolites

“…2), but no apparent consensus sequence has been identified unlike ABC transporters that contain unique ABC signature(s), although three amino acids conserved in one cluster of the MATE family were reported to be essential for the antiport function of bacterial MATEs (Otsuka et al 2005b). The first MATE transporter was identified from the screening of Vibrio parahaemolyticus genes that confer resistance for norfloxacin, a widely used antimicrobial compound (Morita et al 1998). The identified gene product was named NorM and reported to function as a sodium-multidrug antiporter that transport various structurally unrelated compounds (Morita et al 2000).…”