Pathway · 2 proteins
Protein targeting
SRP and docking proteins target selected membrane or exported proteins.
How it works
- Signal-recognition-particle protein and its receptor FtsY participate in targeting selected proteins toward a membrane. Recognition concerns a targeting signal on an emerging protein chain, not the destination of every cellular protein.
- In the representative bacterial SRP mechanism, an SRP complex recognizes the substrate and interacts with FtsY to deliver the translating machinery to a membrane-associated insertion pathway. Nucleotide-dependent rearrangements help coordinate handoff.
- SRP-associated RNA, ribosomes and a compatible membrane pathway are additional partners, not proteins supplied by these two gene annotations. Targeting is distinct from moving the chain through the membrane.
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 |
|---|---|---|---|---|---|
| Signal recognition particle protein | 3.6.5.4 | GTP + H2O = GDP + phosphate + H(+) | — | 454 | Step named |
| Signal recognition particle receptor FtsY | 3.6.5.4 | GTP + H2O = GDP + phosphate + H(+) | — | 461 | Step named |
Origins
How do new proteins find their way to the membrane?
How it was discovered
- 1970sGünter Blobel proposes that proteins carry sorting signals, short sequences that direct them to the right place (Nobel Prize 1999).Brooker, Biology, p. 101
The signal recognition particle is an RNA–protein complex, one of the RNA-containing machines that RNA world proposals point to.
Targeting needs three things that match: a signal sequence in the new protein, the particle that reads it as it leaves the ribosome, and a receptor at the membrane that receives it. Two proteins of the minimal set serve this pathway.
From the books: Brooker, Biology, p. 101; Atkins, Gesteland & Cech (eds.), RNA Worlds, p. 7.
The wider question for this part of the cell: origins for building proteins and folding them.
Sources
- Atlas pathway grouping from the VF5 reference-genome system map (Deckert et al. 1998; Braakman & Smith 2014)
Other pathways in this group: Ribosomal subunits · Translation interface · RNA maturation · Translation cycle · Protein translocation · Protein turnover · Folding and stabilization · Recycling and rescue · Early folding support · Ribosome · Protein export · Not yet placed in a pathway