This family is the Small Multidrug Resistance (SMR) family. Several members have been shown to export a range of toxins, including ethidium bromide ([1] and quaternary ammonium compounds [2], through coupling with proton influx [3].

1: Nucleotide sequence of a gene that encodes resistance to ethidium bromide from a transferable plasmid in Staphylococcus aureus. Sasatsu M, Shima K, Shibata Y, Kono M; Nucleic Acids Res 1989;17:10103-10103. PMID:2602117

2: The chloramphenicol acetyltransferase gene of Tn2424: a new breed of cat. Parent R, Roy PH; J Bacteriol 1992;174:2891-2897. PMID:1314803

3: EmrE, an Escherichia coli 12-kDa multidrug transporter, exchanges toxic cations and H+ and is soluble in organic solvents. Yerushalmi H, Lebendiker M, Schuldiner S; J Biol Chem 1995;270:6856-6863. PMID:7896833