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Signal sequence-independent SRP-SR complex formation at the membrane suggests an alternative targeting pathway within the SRP cycle.
- Source :
-
Molecular biology of the cell [Mol Biol Cell] 2011 Jul 01; Vol. 22 (13), pp. 2309-23. Date of Electronic Publication: 2011 May 05. - Publication Year :
- 2011
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Abstract
- Protein targeting by the signal recognition particle (SRP) and the bacterial SRP receptor FtsY requires a series of closely coordinated steps that monitor the presence of a substrate, the membrane, and a vacant translocon. Although the influence of substrate binding on FtsY-SRP complex formation is well documented, the contribution of the membrane is largely unknown. In the current study, we found that negatively charged phospholipids stimulate FtsY-SRP complex formation. Phospholipids act on a conserved positively charged amphipathic helix in FtsY and induce a conformational change that strongly enhances the FtsY-lipid interaction. This membrane-bound, signal sequence-independent FtsY-SRP complex is able to recruit RNCs to the membrane and to transfer them to the Sec translocon. Significantly, the same results were also observed with an artificial FtsY-SRP fusion protein, which was tethered to the membrane via a transmembrane domain. This indicates that substrate recognition by a soluble SRP is not essential for cotranslational targeting in Escherichia coli. Our findings reveal a remarkable flexibility of SRP-dependent protein targeting, as they indicate that substrate recognition can occur either in the cytosol via ribosome-bound SRP or at the membrane via a preassembled FtsY-SRP complex.
- Subjects :
- Endopeptidase K metabolism
Escherichia coli metabolism
Escherichia coli Proteins chemistry
Escherichia coli Proteins metabolism
Guanosine Triphosphate metabolism
Membrane Proteins metabolism
Phospholipids metabolism
Protein Binding
Protein Structure, Tertiary
Protein Transport
Recombinant Fusion Proteins metabolism
Ribonuclease III metabolism
Ribosomes metabolism
Structure-Activity Relationship
Bacterial Proteins chemistry
Bacterial Proteins metabolism
Calcium-Binding Proteins metabolism
Membrane Glycoproteins metabolism
Receptors, Cytoplasmic and Nuclear chemistry
Receptors, Cytoplasmic and Nuclear metabolism
Receptors, Peptide metabolism
Signal Recognition Particle chemistry
Signal Recognition Particle metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 1939-4586
- Volume :
- 22
- Issue :
- 13
- Database :
- MEDLINE
- Journal :
- Molecular biology of the cell
- Publication Type :
- Academic Journal
- Accession number :
- 21551068
- Full Text :
- https://doi.org/10.1091/mbc.E11-02-0152