This family is comprised of fungal proteins with multiple transmembrane regions. RTA1 (Swiss:P53047) is involved in resistance to 7-aminocholesterol [1], while RTM1 (Swiss:P40113) confers resistance to an an unknown toxic chemical in molasses [2]. These proteins may bind to the toxic substance, and thus prevent toxicity. They are not thought to be involved in the efflux of xenobiotics [1].

1: Characterization of the Saccharomyces cerevisiae RTA1 gene involved in 7-aminocholesterol resistance. Soustre I, Letourneux Y, Karst F; Curr Genet 1996;30:121-125. PMID:8660468

2: RTM1: a member of a new family of telomeric repeated genes in yeast. Ness F, Aigle M; Genetics 1995;140:945-956. PMID:7672593