Some members of this family have been proposed to function as a thallium-specific efflux pump [1].

1: Mutant phenotypes for thousands of bacterial genes of unknown function. Price MN, Wetmore KM, Waters RJ, Callaghan M, Ray J, Liu H, Kuehl JV, Melnyk RA, Lamson JS, Suh Y, Carlson HK, Esquivel Z, Sadeeshkumar H, Chakraborty R, Zane GM, Rubin BE, Wall JD, Visel A, Bristow J, Blow MJ, Arkin AP, Deutschbauer AM; Nature. 2018;557:503-509. PMID:29769716