CHR, a Novel Family of Prokaryotic Proton Motive Force-Driven Transporters Probably Containing Chromate/Sulfate Antiporters

We describe a small family of proteins, CHR, which contains members that function in chromate and/or sulfate transport. CHR proteins occur in bacteria and archaea. They consist of about 400 amino acyl residues, appear to have 10 transmembrane α-helical segments in an unusual 4+6 arrangement, and arose by an intragenic duplication event.