This family of transporters has ten alpha helical transmembrane segments. The structure of a bacterial homolog of SLAC1 shows it to have a trimeric arrangement. The pore is composed of five helices with a conserved Phe residue involved in gating. One homolog, Mae1 from the yeast Schizosaccharomyces pombe, functions as a malate uptake transporter; another, Ssu1 from Saccharomyces cerevisiae and other fungi including Aspergillus fumigatus, is characterized as a sulfite efflux pump; and TehA from Escherichia coli is identified as a tellurite resistance protein by virtue of its association in the tehA/tehB operon. In plants, this family is found in the stomatal guard cells functioning as an anion-transporting pore. Many homologs are incorrectly annotated as tellurite resistance or dicarboxylate transporter (TDT) proteins.