1. Multidrug and toxic compound extrusion (MATE)-type transporters, which were first identified as a bacterial drug transporter family, are present in almost all prokaryotes and eukaryotes, and are thus one of the mostly conserved transporter families in nature. 2. Recently, a mammalian MATE transporter was shown to be a long hypothesized electroneutral H(+)/organic cation exporter that is responsible for the excretion of metabolic waste products and xenobiotics at renal brush border membranes and bile canaliculi. Plant MATE-type transporters are involved in the detoxification of metals and secondary metabolites such as phenols through their vesicular storage or extrusion at the plasma membrane. 3. Thus, MATE transporters are involved in one of the basic mechanisms that maintain homeostasis through the excretion of metabolic waste products and xenobiotics in nature.