Structure of the SecY Complex Unlocked by a Preprotein Mimic

Hizlan, Dilem; Robson, Alice; Whitehouse, Sarah L.; Gold, Vicki A. M.; Vonck, Janet; Mills, Deryck J.; Kühlbrandt, Werner; Collinson, Ian

doi:10.1016/j.celrep.2011.11.003

Cited by 63 publications

(98 citation statements)

References 38 publications

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“…We also did not observe any PpiD cross-linking product when pBpa was incorporated into the N terminus of SecG (Fig. 3), which is located close to helix 3 of the lateral gate (16,46). In summary, these data show that PpiD is positioned in immediate vicinity to the lateral gate of SecY where it contacts all four helices of the lateral gate.…”

Section: The Lack Of Ppid Does Not Significantly Impair In Vitro Proteinmentioning

confidence: 51%

“…In conclusion, neither SecA nor ribosome binding to SecY significantly influenced the interaction of PpiD with the lateral gate of SecY. (46) and to allow transmembrane domains to enter the lipid phase of the membrane (52,54). Recent Cryo-EM structures have visualized significant movements at the lateral gate after docking of RNCs onto SecY (52,54).…”

Section: The Lack Of Ppid Does Not Significantly Impair In Vitro Proteinmentioning

confidence: 99%

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Dynamic Interaction of the Sec Translocon with the Chaperone PpiD

Sachelaru

Petriman

Kudva

et al. 2014

Journal of Biological Chemistry

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Section: The Lack Of Ppid Does Not Significantly Impair In Vitro Proteinmentioning

confidence: 51%

Section: The Lack Of Ppid Does Not Significantly Impair In Vitro Proteinmentioning

confidence: 99%

Dynamic Interaction of the Sec Translocon with the Chaperone PpiD

Sachelaru

Petriman

Kudva

et al. 2014

Journal of Biological Chemistry

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“…Previous MD simulations (19) and cryo-electron microscopy structures (24,25) suggested that the plug might not completely leave its cavity in the translocon, but only move sideways to accommodate the translocating peptide. Indeed, immobilization of the plug inside bacterial SecYEG did not impair functionality of the translocon (26).…”

Section: Discussionmentioning

confidence: 99%

Functional asymmetry within the Sec61p translocon

Demirci

Junne

Baday

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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The Sec61 translocon forms a pore to translocate polypeptide sequences across the membrane and offers a lateral gate for membrane integration of hydrophobic (H) segments. A central constriction of six apolar residues has been shown to form a seal, but also to determine the hydrophobicity threshold for membrane integration: Mutation of these residues in yeast Sec61p to glycines, serines, aspartates, or lysines lowered the hydrophobicity required for integration; mutation to alanines increased it. Whereas four leucines distributed in an oligo-alanine H segment were sufficient for 50% integration, we now find four leucines in the N-terminal half of the H segment to produce significantly more integration than in the C-terminal half, suggesting functional asymmetry within the translocon. Scanning a cluster of three leucines through an oligo-alanine H segment showed high integration levels, except around the position matching that of the hydrophobic constriction in the pore where integration was strongly reduced. Both asymmetry and the position effect of H-segment integration disappeared upon mutation of the constriction residues to glycines or serines, demonstrating that hydrophobicity at this position within the translocon is responsible for the phenomenon. Asymmetry was largely retained, however, when constriction residues were replaced by alanines. These results reflect on the integration mechanism of transmembrane domains and show that membrane insertion of H segments strongly depends not only on their intrinsic hydrophobicity but also on the local conditions in the translocon interior. Thus, the contribution of hydrophobic residues in the H segment is not simply additive and displays cooperativeness depending on their relative position.protein translocation | transmembrane helix T he conserved Sec61/SecY translocon provides a passage for hydrophilic polypeptide sequences across the membrane of the endoplasmic reticulum (ER) or the bacterial plasma membrane (1). It consists of Sec61α (Sec61p in yeast) with 10 transmembrane domains and the single spanning proteins Sec61β (Sbh1p) and Sec61γ (Sss1p), corresponding in bacteria to SecY/ SecG/SecE. The translocon forms a compact helix bundle that can open a pore across the membrane with a lateral gate toward the lipid membrane. In the idle state, the central pore is closed by a constriction of six, almost invariably hydrophobic side chains and a luminal plug helix. The plug closes and stabilizes the inactive translocon and is displaced by translocating peptides, while the constriction residues form a gasket around them, keeping the translocon sealed to ions and small molecules (2-4).The lateral gate allows transmembrane helices (TMs) to insert into the lipid phase. Systematic quantitative analyses of membrane integration of mildly hydrophobic sequences (H segments) defined the contribution of each amino acid to the probability of insertion into or transfer across the bilayer (5-9). These studies yielded "biological hydrophobicity scales," similar to scales determined b...

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“…It is clear that the channel for transfer of polypeptides lies within a monomer of SecY (1,(15)(16)(17)(18); however, SecYEG exists as monomers, dimers, and higher oligomers (19)(20)(21)(22)(23)(24). Therefore, much controversy has arisen surrounding the question of whether the active translocase comprises a SecYEG monomer or dimer (17,(25)(26)(27)(28).…”

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confidence: 99%

Stoichiometry of SecYEG in the active translocase of Escherichia coli varies with precursor species

Mao

Cheadle²,

Hardy

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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We have established a reconstitution system for the translocon SecYEG in proteoliposomes in which 55% of the accessible translocons are active. This level corresponds to the fraction of translocons that are active in vitro when assessed in their native environment of cytoplasmic membrane vesicles. Assays using these robust reconstituted proteoliposomes and cytoplasmic membrane vesicles have revealed that the number of SecYEG units involved in an active translocase depends on the precursor undergoing transfer. The active translocase for the precursor of periplasmic galactose-binding protein contains twice the number of heterotrimeric units of SecYEG as does that for the precursor of outer membrane protein A.

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Structure of the SecY Complex Unlocked by a Preprotein Mimic

Cited by 63 publications

References 38 publications

Dynamic Interaction of the Sec Translocon with the Chaperone PpiD

Dynamic Interaction of the Sec Translocon with the Chaperone PpiD

Functional asymmetry within the Sec61p translocon

Stoichiometry of SecYEG in the active translocase of Escherichia coli varies with precursor species

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