Cadmium resistance transporter explained

The cadmium resistance (CadD) protein family (TC# 2.A.77) belongs to the Lysine exporter (LysE) superfamily.^[1] CadD members facilitate the export of cationic compounds such as cadmium ions.^[2]

Members

Currently, many 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 function in quaternary ammonium cation export, and the fourth is a distant open reading frame (ORF) in Staphylococcus aureus.^[3] These proteins are found in Gram-positive bacteria. Their mode of energy coupling has not been investigated, but is hypothesized to include a proton antiport mechanism. 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 are included in the LysE superfamily, all consist of proteins of similar sizes (about 200 residues) and topologies (6 putative transmembrane α-helical segments; 5 experimentally determined TMSs).^[4]

General Transport Reaction

The probable reaction catalyzed by these proteins is:

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

Further reading

• Schirawski J, Hagens W, Fitzgerald GF, Van Sinderen D . Molecular characterization of cadmium resistance in Streptococcus thermophilus strain 4134: an example of lateral gene transfer . Applied and Environmental Microbiology . 68 . 11 . 5508–16 . November 2002 . 12406744 . 129935 . 10.1128/AEM.68.11.5508-5516.2002 . 2002ApEnM..68.5508S .
• Johnson DA, Tetu SG, Phillippy K, Chen J, Ren Q, Paulsen IT . High-throughput phenotypic characterization of Pseudomonas aeruginosa membrane transport genes . PLOS Genetics . 4 . 10 . e1000211 . October 2008 . 18833300 . 2542419 . 10.1371/journal.pgen.1000211 . free .
• Nies DH . Resistance to cadmium, cobalt, zinc, and nickel in microbes . Plasmid . 27 . 1 . 17–28 . January 1992 . 1741458 . 10.1016/0147-619X(92)90003-S.
• Braz VS, Marques MV . Genes involved in cadmium resistance in Caulobacter crescentus . FEMS Microbiology Letters . 251 . 2 . 289–95 . October 2005 . 16168577 . 10.1016/j.femsle.2005.08.013 . free .
• Lee SW, Glickmann E, Cooksey DA . Chromosomal locus for cadmium resistance in Pseudomonas putida consisting of a cadmium-transporting ATPase and a MerR family response regulator . Applied and Environmental Microbiology . 67 . 4 . 1437–44 . April 2001 . 11282588 . 92752 . 10.1128/AEM.67.4.1437-1444.2001 . 2001ApEnM..67.1437L .

Notes and References

1. Tsu BV, Saier MH . The LysE Superfamily of Transport Proteins Involved in Cell Physiology and Pathogenesis . PLOS ONE . 10 . 10 . e0137184 . 2015-01-01 . 26474485 . 4608589 . 10.1371/journal.pone.0137184 . 2015PLoSO..1037184T . free .
2. Web site: 2.A.77 The Cadmium Resistance (CadD) Family . Transporter Classification Database . 2016-02-25 .
3. Crupper SS, Worrell V, Stewart GC, Iandolo JJ . Cloning and expression of cadD, a new cadmium resistance gene of Staphylococcus aureus . Journal of Bacteriology . 181 . 13 . 4071–5 . July 1999 . 10.1128/JB.181.13.4071-4075.1999 . 10383976 . 93898 .
4. Cao Y, Jin X, Levin EJ, Huang H, Zong Y, Quick M, Weng J, Pan Y, Love J, Punta M, Rost B, Hendrickson WA, Javitch JA, Rajashankar KR, Zhou M . Crystal structure of a phosphorylation-coupled saccharide transporter . Nature . 473 . 7345 . 50–4 . May 2011 . 21471968 . 3201810 . 10.1038/nature09939 . 2011Natur.473...50C .