The cation-chloride cotransporter (CCC) family (TC# 2.A.30) is part of the APC superfamily of secondary carriers.
Most characterized CCC family proteins are from higher eukaryotes, but one has been partially characterized from Nicotiana tabacum (a plant), and homologous ORFs have been sequenced from Caenorhabditis elegans (worm), Saccharomyces cerevisiae (yeast) and Synechococcus sp.
[4] Each of the major types of CCC family members in mammals exist as paralogous isoforms.
Warmuth et al. (2009) determined the x-ray structure of the C-terminal domain of a CCC from the archaeon Mehanosarcina acetivorans (PDB: 3G40).
[7] It shows a novel fold of a regulatory domain, distantly related to universal stress proteins.