This small domain is found in a family of proteins with the Pfam:PF01595 domain and two CBS domains with this domain found at the C-terminus of the proteins, the domain is also found at the C terminus of some Na+/H+ antiporters. This domain is also found in CorC that is involved in Magnesium and cobalt efflux. The function of this domain is uncertain but might be involved in modulating transport of ion substrates.