2.A.77 The Cadmium Resistance (CadD) Family
Four currently sequenced proteins comprise the CadD family. Two are close orthologues in two Staphylococcus species that have been reported to function in cadmium resistance, a third has been reported to possibly function in quaternary ammonium ion export, and the fourth is a distant ORF in Staphylococcus aureus. These proteins are found in Gram-positive bacteria. Their mode of energy coupling has not been investigated, but a proton antiport mechanism is probable. Based on PSI-BLAST results, this family is distantly related to members of the LysE family (TC #2.A.75) and the RhtB family (TC #2.A.76). These three families, which comprise the LysE superfamily, all consist of proteins of similar sizes (about 200 residues) and topologies (6 putative transmembrane
The probable reaction catalyzed by these proteins is:
Cationic compound (in) + nH+ (out) Cationic compound (out) + nH+ (in).