2.A.77 The Cadmium Resistance (CadD) Family

Many 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 fourth 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. 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 α-helical segments, TMSs; 5 experimentally determined TMSs).

The probable reaction catalyzed by these proteins is:

Cationic compound (in) + nH+ (out) Cationic compound (out) + nH+ (in)

This family belongs to the LysE Superfamily.



Cao, Y., X. Jin, E.J. Levin, H. Huang, Y. Zong, M. Quick, J. Weng, Y. Pan, J. Love, M. Punta, B. Rost, W.A. Hendrickson, J.A. Javitch, K.R. Rajashankar, and M. Zhou. (2011). Crystal structure of a phosphorylation-coupled saccharide transporter. Nature 473: 50-54.

Crupper, S.S., V. Worrell, G.C. Stewart, and J.J. Iandolo. (1999). Cloning and expression of cadD, a new cadmium resistance gene of Staphylococcus aureus. J. Bacteriol. 181: 4071-4075.

Johnson, D.A., S.G. Tetu, K. Phillippy, J. Chen, Q. Ren, and I.T. Paulsen. (2008). High-throughput phenotypic characterization of Pseudomonas aeruginosa membrane transport genes. PLoS Genet 4: e1000211.


TC#NameOrganismal TypeExample
2.A.77.1.1Cadmium resistance protein CadD encoded on plasmid pRW001 Gram-positive bacteria CadD of Staphylococcus aureus
2.A.77.1.2Putative quaternary amine transporter, QacF Gram-positive bacteria QacF of Bacillus firmus



CadD of Lactobacillus fermentum


CadD of 255 aas


CadD of Mycobacterium gilvum


CadD of 192 aas


CadD of Natronomonas pharaonis