Protein traffic in bacteria: Multiple routes from the ribosome to and across the membrane

Müller, Matthias; Koch, Hans‐Georg; Beck, Konstanze; Schäfer, Ute

doi:10.1016/s0079-6603(00)66028-2

Cited by 125 publications

(98 citation statements)

References 290 publications

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“…Interestingly, the non-folded state of proteins secreted through the membrane into the periplasm via the translocon resembles that of cytosolic proteins emerging at the exit of the ribosomal tunnel. Consistent with this, the periplasm harbours a specialized subset of chaperones, which have to cover the same tasks as cytosolic chaperones and in addition have to ensure correct disulfide bond formation [8].…”

Section: Bacterial Chaperonesmentioning

confidence: 73%

“…the access of SRPs to N-terminal signal sequences and is capable of keeping emerging polypeptides in a translocation-competent non-native conformation [8,9]. Interestingly, the non-folded state of proteins secreted through the membrane into the periplasm via the translocon resembles that of cytosolic proteins emerging at the exit of the ribosomal tunnel.…”

Section: Bacterial Chaperonesmentioning

confidence: 99%

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A cradle for new proteins: trigger factor at the ribosome

Maier

Ferbitz

Deuerling

et al. 2005

Current Opinion in Structural Biology

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Newly synthesized proteins leave the ribosome through a narrow tunnel in the large subunit. During ongoing synthesis, nascent protein chains are particularly sensitive to aggregation and degradation because they emerge from the ribosome in an unfolded state. In bacteria, the first protein to interact with nascent chains and facilitate their folding is the ribosomeassociated chaperone trigger factor. Recently, crystal structures of trigger factor and of its ribosome-binding domain in complex with the large ribosomal subunit revealed that the chaperone adopts an extended 'dragon-shaped' fold with a large hydrophobic cradle, which arches over the exit of the ribosomal tunnel and shields newly synthesized proteins. These structural results, together with recent biochemical data on trigger factor and its interplay with other chaperones and factors that interact with the nascent chain, provide a comprehensive view of the role of trigger factor during cotranslational protein folding.

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Section: Bacterial Chaperonesmentioning

confidence: 73%

Section: Bacterial Chaperonesmentioning

confidence: 99%

A cradle for new proteins: trigger factor at the ribosome

Maier

Ferbitz

Deuerling

et al. 2005

Current Opinion in Structural Biology

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“…The specialized function of SecB in the targeting of secretory proteins to the sec translocon has been well documented (11,22,23), whereas its active participation in the folding of cytosolic proteins has been suggested (13,33). In agreement with a role for SecB as a generalized chaperone, previous in vitro studies indicated that SecB has no specific affinity for signal sequences (12,13).…”

Section: Discussionmentioning

confidence: 84%

“…In a search for additional cellular factors that could assist folding of newly synthesized proteins, we found that plasmid pE01, which contains an E. coli genomic fragment encompassing the yibN, grxC, secB, and gpsA genes, could partially suppress the ts phenotype of the ⌬tig ⌬dnaKdnaJ triple null mutant (data not shown). We asked whether SecB, a chaperone involved in the SecA͞SecB-dependent secretion pathway (11,22,23), is responsible for the suppressive effect. To address this question, we PCR amplified and cloned the secB ORF under the control of an IPTG-inducible promoter on both a low (p29SEN) and a high (pSE380⌬NcoI) copy number plasmid and tested its ability to complement the ts phenotype of the ⌬tig ⌬dnaKdnaJ mutant.…”

Section: Secb Overexpression Efficiently Suppresses the Growth Defectmentioning

confidence: 99%

SecB is a bona fide generalized chaperone in Escherichia coli

Ullers

Luirink

Harms

et al. 2004

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

108

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It is known that the DnaK and Trigger Factor (TF) chaperones cooperate in the folding of newly synthesized cytosolic proteins in Escherichia coli. We recently showed that despite a very narrow temperature range of growth and high levels of aggregated cytosolic proteins, E. coli can tolerate deletion of both chaperones, suggesting that other chaperones might be involved in this process. Here, we show that the secretion-dedicated chaperone SecB efficiently suppresses both the temperature sensitivity and the aggregation-prone phenotypes of a strain lacking both TF and DnaK. SecB suppression is independent of a productive interaction with the SecA subunit of the translocon. Furthermore, in vitro cross-linking experiments demonstrate that SecB can interact both co-and posttranslationally with short nascent chains of both secretory and cytosolic proteins. Finally, we show that such cotranslational substrate recognition by SecB is greatly suppressed in the presence of ribosome-bound TF, but not by DnaK. Taken together, our data demonstrate that SecB acts as a bona fide generalized chaperone.

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“…In bacteria, most of the exported proteins cross the cytosolic membrane through the Sec-dependent translocase in an unfolded conformation (1)(2)(3). A subset of proteins is transported via the twin arginine translocation (Tat) 2 pathway.…”

mentioning

confidence: 99%

Affinity of TatCd for TatAd Elucidates Its Receptor Function in the Bacillus subtilis Twin Arginine Translocation (Tat) Translocase System

Schreiber

Stengel

Westermann

et al. 2006

Journal of Biological Chemistry

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Twin arginine translocation (Tat) systems catalyze the transport of folded proteins across the bacterial cytosolic membrane or the chloroplast thylakoid membrane. In the Tat systems of Escherichia coli and many other species TatA-, TatB-, and TatClike proteins have been identified as essential translocase components. In contrast, the Bacillus subtilis phosphodiesterase PhoD-specific system consists only of a pair of TatA In bacteria, most of the exported proteins cross the cytosolic membrane through the Sec-dependent translocase in an unfolded conformation (1-3). A subset of proteins is transported via the twin arginine translocation (Tat) 2 pathway. This alternative route accepts folded proteins or protein domains as substrates (4 -6). Initially, the Tat pathway was discovered in chloroplasts as a pathway that operates independently of soluble factors and nucleoside triphosphates and is exclusively energized by the proton gradient across the membrane (7-9). In vitro translocation systems using Escherichia coli components demonstrated that also in bacteria this transport system is energized exclusively by the transmembrane proton electrochemical gradient (10,11). Substrates destined for export by the Tat system are synthesized as preproteins with a signal peptide containing an almost invariant twin arginine sequence motif in the N-region of the otherwise canonically structured signal sequence (12).In E. coli TatA, TatB, and TatC proteins have been demonstrated to be essential for Tat-dependent protein transport (13-16). The TatA homologous protein TatE has been proven to be functionally redundant (17). In chloroplasts structural and functional counterparts Tha4 (homologous to TatA; Ref. 18), Hcf106 (homologous to TatB; Refs. 16, 19), and cpTatC (homologous to TatC; Ref. 20) have been identified. The sequence-related proteins TatA and TatB are anchored in the cytoplasmic membrane via an amino-proximal ␣-helical domain (13). TatCs are a family of proteins with six calculated transmembrane-spanning domains with N and C termini exposed to the cytoplasmic or stromal side of the membrane (4). Gouffi et al. (21) recently proposed function-linked changes of TatA and TatC topologies for the mechanism of folded protein translocation in E. coli. These changes involve a TatA, the C terminus of which shuttles between the cytosol and the periplasmic space, and a TatC, the predicted fourth and fifth transmembrane helices of which shuttle in the periplasmic space. They speculated that this topology of TatC might reflect an operational state of TatC that changes during the protein translocation process (21). The current proposal for the action of Tat transport system of E. coli and plant thylakoids involves the initial binding of substrates to the TatB-TatC high molecular weight complex mediated via a direct contact of the double arginine signal peptide with TatC (20,22). The signal peptide binding triggers association with TatA to form the active translocation channel driven by the transmembrane proton electrochemical gradien...

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Protein traffic in bacteria: Multiple routes from the ribosome to and across the membrane

Cited by 125 publications

References 290 publications

A cradle for new proteins: trigger factor at the ribosome

A cradle for new proteins: trigger factor at the ribosome

SecB is a bona fide generalized chaperone in Escherichia coli

Affinity of TatCd for TatAd Elucidates Its Receptor Function in the Bacillus subtilis Twin Arginine Translocation (Tat) Translocase System

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