A number of proteins, the majority of which are involved in the transport of anions across a membrane as well as some yet uncharacterized proteins have been shown [1,2] to be evolutionary related. These proteins are:

• Mammalian sulfate anion transporter 1 (SAT-1) (gene SLC26A1).
• Mammalian DTDST (gene SLC26A2), a sulfate transporter which, in Human, is involved in the genetic disease, diastrophic dysplasia (DTD).
• Mammalian chloride anion exchanger (DRA) (gene SLC26A3).
• Mammalian pendrin (PDS) (gene SLC26A4), a chloride/iodide transporter which in Human is involved in a number of hearing loss genetic diseases.
• Mammalian prestin (gene SLC26A5), a motor protein that converts auditory stimuli to length changes in outer hair cells and mediates sound amplification in the mammalian hearing organ. Prestin is, so far, the only member of this family whose direct function is not to transport ion across a membrane.
• Mammalian SLC26A6, whose function is not yet known.
• Neurospora crassa sulfate permease II (gene cys-14).
• Yeast sulfate permeases (genes SUL1 and SUL2).
• Sulfate transporters 1, 2 and 3 from the legume Stylosanthes hamata.
• Soybean early nodulin 70.
• Escherichia coli hypothetical protein ychM.
• Caenorhabditis elegans hypothetical protein F41D9.5.

As expected by their transport function, these proteins are highly hydrophobic and seem to contain about 12 transmembrane domains. The best conserved region seems to be located in the second transmembrane region and is used as a signature pattern.