| 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)
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This family belongs to the LysE Superfamily.
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| References: |
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.
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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.
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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.
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| Examples: |
| TC# | Name | Organismal Type | Example |
| 2.A.77.1.1 | Cadmium resistance protein CadD encoded on plasmid pRW001 | Gram-positive bacteria | CadD of Staphylococcus aureus |
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| 2.A.77.1.2 | Putative quaternary amine transporter, QacF | Gram-positive bacteria | QacF of Bacillus firmus |
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| 2.A.77.1.3 | CadD | Firmicutes | CadD of Lactobacillus fermentum |
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| 2.A.77.1.4 | CadD of 255 aas | Actinobacteria | CadD of Mycobacterium gilvum |
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| 2.A.77.1.5 | CadD of 192 aas | Euryarchaea | CadD of Natronomonas pharaonis |
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