ABC Transporters
Description: ABC (ATP-bound cassette) Transporters are a combination of membrane proteins that together create a superfamily. They can translocate many substrates across intracellular and extracellular membranes. The substrates include drugs, metabolic products and carbohydrates. They are useful for curing certain diseases, specifically cystic fibrosis, tumor resistance, as well as bacterial multi-drug resistance.
The name ABC-transporters for this pathway was given in 1990, a few years after discovering the actual mechanisms for prokaryotes and eukaryotes. Prokaryotes were discovered to have this pathway in 1982, whereas in eukaryotes, it was found four years later in 1986. The precise mechanism for this pathway is still up for debate, but it is known that substrates are passed through the membrane by active transport. The energy that couples this active transport comes from the hydrolysis of ATP into ADP. It was thought previously that an electrochemical gradient may play a part in the transport of substrates but eventually was disproved when there was no such gradient located.
The structure of these transporters can be separated into two major components: transmembrane domains (TMDs) and nucleotide-binding domains (NBDs). TMDs can be broken down into two different sites; each are composed of six alpha-helices that span the entire membrane. There are three different folds in TMDs, which are, a type I importer, a type II importer, and an ABC exporter. NBDs can also be broken down into two different sites, one small and one large. The larger site contains two beta-sheets and six alpha helices. This is where the ATP binding occurs. The protein sequence of an NBD is very similar in different kinds of organisms, which reduces the amount of mutations within it.
These transmembrane proteins can have different functions depending on whether they are an importer or an exporter. In humans, there are 48 subfamilies of both importers and exporters, whereas in prokaryotes, there are 25 kinds of importers and 29 kinds of exporters. The function of importers in ABC-transport is to mediate the uptake of nutrients. The way this is done is by way of binding proteins. A role of the exporters is to secrete drugs and other antibiotics out of the cell which contributes to cell's resistance to those drugs. This occurs because of an overexpression of ABC-transporters.
Related BMRB Molecules
- N-Acetyl-D-Glucosamine
- L-Alanine
- D-Allose
- 2-Aminoethylphosphonic Acid
- L-Arabinose
- L-Arginine
- L-Aspartic Acid
- Betaine
- (+)-Biotin
- D-Carnitine
- D-Cellobiose
- Choline
- L-Cystine
- i(L)-Erythritol
- D-Fructose
- L-Fucose
- D-Galacturonic Acid
- D-Glucose
- L-Glutamic Acid
- L-Glutamine
- L-Glutathione, Oxidized
- Glycerol
- DL-alpha Glycerol Phosphate
- Glycine
- L-Histidine
- myo-Inositol
- L-Isoleucine
- Lactose
- L-Leucine
- L-Lysine
- D-Maltose
- D-Mannitol
- D-Mannose
- Melibiose
- D-Methionine
- L-Ornithine
- L-Phenylalanine
- Polygalacturonic Acid
- L-Proline
- Raffinose
- L-Serine
- D-Sorbitol
- Spermidine
- Stachyose
- Taurine
- Thiamin
- L-Threonine
- D-Trehalose
- L-Valine
- Xylitol
- 1,4-D-Xylobiose
- D-Xylose
For complete information about pathway, see KEGG [map02010]