Pathway · 14 proteins
ATP-coupled transport
ATPase and permease annotations identify ABC transport machinery.
How it works
- The module groups ABC transporter ATP-binding components and membrane permeases. Examples include Pst phosphate-uptake components and annotations associated with molybdate, metals, lipid transport or LPS export.
- In a representative ABC cycle, nucleotide binding and hydrolysis couple changes in the cytosolic ATPase to changes in the membrane pathway. Uptake and export systems have different architectures and substrate-delivery requirements.
- Transport moves a selected cargo across a membrane; it does not chemically synthesize that cargo. Matching ATPases to permeases, establishing direction and measuring coupling require transporter-specific evidence.
Grouped by the atlas’s curated pathway map. The table order is not a proven reaction order.
Its proteins
| Protein | EC | Reaction (UniProt) | Metal or cluster | Amino acids | Certainty |
|---|---|---|---|---|---|
| Phosphate import ATP-binding protein PstB | 7.3.2.1 | phosphate(out) + ATP + H2O = ADP + 2 phosphate(in) + H(+) | — | 257 | Step named |
| ABC transporter | — | — | Mg(2+) | 396 | Step named |
| Transport permease protein | — | — | — | 256 | Step named |
| Iron export ABC transporter permease subunit FetB | — | — | — | 244 | System only |
| ABC transporter | — | — | — | 247 | Step named |
| Phosphate transport system permease protein | — | — | — | 320 | Step named |
| Phosphate transport system permease protein PstA | — | — | — | 285 | Step named |
| ABC transporter | — | — | — | 305 | Step named |
| ABC transporter | — | — | — | 251 | Step named |
| Metal ABC transporter permease | — | — | — | 245 | System only |
| ABC transporter permease | — | — | — | 416 | Step named |
| ABC transporter permease | — | — | — | 245 | Step named |
| ABC transporter | — | — | — | 232 | Step named |
| Uncharacterized protein | — | — | — | 243 | System only |
Also part of this pathway
These proteins are described under another pathway, but also take part here.
| Protein | EC | Reaction (UniProt) | Metal or cluster | Amino acids | Certainty |
|---|---|---|---|---|---|
| ABC transporter (MsbA subfamily)Home: Substrate recognition | — | — | — | 554 | Step named |
| Lipoprotein-releasing system ATP-binding protein LolDHome: Substrate recognition | 7.6.2.- | — | — | 224 | Step named |
| Lipopolysaccharide export system ATP-binding protein LptBHome: Substrate recognition | — | — | — | 238 | Step named |
Origins
How could nutrients enter a cell, against a concentration gradient, before ATP-driven transporters existed?
How it was discovered
- 1940sActive transport is discovered in studies of how sodium and potassium move across the membranes of muscle cells, nerve cells and red blood cells.Brooker, Biology, PDF p. 149
Large molecules can be enclosed in lipid vesicles under simulated prebiotic conditions. Zubay suggests that the first membranes may have hindered the flow of nutrients inward, and that the first proteins crossing the membrane worked as simple pores.
A membrane that keeps the cell's contents in also keeps nutrients out. ABC transporters solve this by spending ATP to pump specific molecules inward, and fourteen proteins of the minimal set belong to this pathway.
The membrane, the energy supply and the transporters must be present together for the cell to feed.
From the books: Brooker, Biology, PDF p. 149; Zubay, Origins of Life on Earth and in the Cosmos, p. 353.
The wider question for this part of the cell: origins for pulling nutrients in from outside.
Sources
- Atlas pathway grouping from the VF5 reference-genome system map (Deckert et al. 1998; Braakman & Smith 2014)
Other pathways in this group: Ion exchange · Potassium balance · Channels and ion uptake · Substrate recognition · Not yet placed in a pathway