scholarly journals Signal peptide hydrophobicity modulates interaction with the twin-arginine translocase

2017 ◽  
Author(s):  
Qi Huang ◽  
Tracy Palmer
Keyword(s):  
Signal Peptide ◽  
Secretory Pathway ◽  
Recognition Site ◽  
Signal Peptides ◽  
Tat Pathway ◽  
Folded Proteins ◽  
Twin Arginine Translocase ◽  
Critical Requirement ◽  
Highly Hydrophobic ◽  
Peptide Hydrophobicity

AbstractThe general secretory pathway (Sec) and twin-arginine translocase (Tat) operate in parallel to export proteins across the cytoplasmic membrane of prokaryotes and the thylakoid membrane of plant chloroplasts. Substrates are targeted to their respective machineries by N-terminal signal peptides that share a common tripartite organization, however Tat signal peptides harbor a conserved and almost invariant arginine pair that are critical for efficient targeting to the Tat machinery. Tat signal peptides interact with a membrane-bound receptor complex comprised of TatB and TatC components, with TatC containing the twin-arginine recognition site. Here we isolated suppressors in the signal peptide of the Tat substrate, SufI, that restored Tat transport in the presence of inactivating substitutions in the TatC twin-arginine binding site. These suppressors increased signal peptide hydrophobicity, and co-purification experiments indicated that they restored binding to the variant TatBC complex. The hydrophobic suppressors could also act in cis to suppress substitutions at the signal peptide twin-arginine motif that normally prevent targeting to the Tat pathway. Highly hydrophobic variants of the SufI signal peptide containing four leucine substitutions retained the ability to interact with the Tat system. The hydrophobic signal peptides of two Sec substrates, DsbA and OmpA, containing twin lysine residues, were shown to mediate export by the Tat pathway and to co-purify with TatBC. These findings indicate that there is unprecedented overlap between Sec and Tat signal peptides and that neither the signal peptide twin-arginine motif nor the TatC twin-arginine recognition site are essential mechanistic features for operation of the Tat pathway.ImportanceProtein export is an essential process in all prokaryotes, The Sec and Tat export pathways operate in parallel, with the Sec machinery transporting unstructured precursors and the Tat pathway transporting folded proteins. Proteins are targeted to the Tat pathway by N-terminal signal peptides that contain an almost invariant twin-arginine motif. Here we make the surprising discovery that the twin-arginines are not essential for recognition of substrates by the Tat machinery, and that this requirement can be bypassed by increasing the signal peptide hydrophobicity. We further show that signal peptides of bona fide Sec substrates can also mediate transport by the Tat pathway. Our findings suggest that key features of the Tat targeting mechanism have evolved to prevent mis-targeting of substrates to the Sec pathway rather than being a critical requirement for function of the Tat pathway.

scholarly journals Signal Peptide Hydrophobicity Modulates Interaction with the Twin-Arginine Translocase

mBio ◽  
2017 ◽  
Vol 8 (4) ◽  
Author(s):  
Qi Huang ◽  
Tracy Palmer
Keyword(s):  
Signal Peptide ◽  
Secretory Pathway ◽  
Recognition Site ◽  
Signal Peptides ◽  
Tat Pathway ◽  
Folded Proteins ◽  
Twin Arginine Translocase ◽  
Critical Requirement ◽  
Highly Hydrophobic ◽  
Peptide Hydrophobicity

ABSTRACT The general secretory pathway (Sec) and twin-arginine translocase (Tat) operate in parallel to export proteins across the cytoplasmic membrane of prokaryotes and the thylakoid membrane of plant chloroplasts. Substrates are targeted to their respective machineries by N-terminal signal peptides that share a tripartite organization; however, Tat signal peptides harbor a conserved and almost invariant arginine pair that is critical for efficient targeting to the Tat machinery. Tat signal peptides interact with a membrane-bound receptor complex comprised of TatB and TatC components, with TatC containing the twin-arginine recognition site. Here, we isolated suppressors in the signal peptide of the Tat substrate, SufI, that restored Tat transport in the presence of inactivating substitutions in the TatC twin-arginine binding site. These suppressors increased signal peptide hydrophobicity, and copurification experiments indicated that they restored binding to the variant TatBC complex. The hydrophobic suppressors could also act in cis to suppress substitutions at the signal peptide twin-arginine motif that normally prevent targeting to the Tat pathway. Highly hydrophobic variants of the SufI signal peptide containing four leucine substitutions retained the ability to interact with the Tat system. The hydrophobic signal peptides of two Sec substrates, DsbA and OmpA, containing twin lysine residues, were shown to mediate export by the Tat pathway and to copurify with TatBC. These findings indicate that there is unprecedented overlap between Sec and Tat signal peptides and that neither the signal peptide twin-arginine motif nor the TatC twin-arginine recognition site is an essential mechanistic feature for operation of the Tat pathway. IMPORTANCE Protein export is an essential process in all prokaryotes. The Sec and Tat export pathways operate in parallel, with the Sec machinery transporting unstructured precursors and the Tat pathway transporting folded proteins. Proteins are targeted to the Tat pathway by N-terminal signal peptides that contain an almost invariant twin-arginine motif. Here, we make the surprising discovery that the twin arginines are not essential for recognition of substrates by the Tat machinery and that this requirement can be bypassed by increasing the signal peptide hydrophobicity. We further show that signal peptides of bona fide Sec substrates can also mediate transport by the Tat pathway. Our findings suggest that key features of the Tat targeting mechanism have evolved to prevent mistargeting of substrates to the Sec pathway rather than being a critical requirement for function of the Tat pathway.

scholarly journals Specificity of Signal Peptide Recognition in Tat-Dependent Bacterial Protein Translocation

2001 ◽  
Vol 183 (2) ◽  
pp. 604-610 ◽  
Author(s):  
Natascha Blaudeck ◽  
Georg A. Sprenger ◽  
Roland Freudl ◽  
Thomas Wiegert
Keyword(s):  
Fusion Protein ◽  
Signal Peptide ◽  
Protein Translocation ◽  
Signal Peptides ◽  
E Coli ◽  
Amino Terminal ◽  
Twin Arginine Translocation ◽  
Tat Pathway ◽  
Dependent Protein ◽  
Folded Proteins

ABSTRACT The bacterial twin arginine translocation (Tat) pathway translocates across the cytoplasmic membrane folded proteins which, in most cases, contain a tightly bound cofactor. Specific amino-terminal signal peptides that exhibit a conserved amino acid consensus motif, S/T-R-R-X-F-L-K, direct these proteins to the Tat translocon. The glucose-fructose oxidoreductase (GFOR) ofZymomonas mobilis is a periplasmic enzyme with tightly bound NADP as a cofactor. It is synthesized as a cytoplasmic precursor with an amino-terminal signal peptide that shows all of the characteristics of a typical twin arginine signal peptide. However, GFOR is not exported to the periplasm when expressed in the heterologous host Escherichia coli, and enzymatically active pre-GFOR is found in the cytoplasm. A precise replacement of the pre-GFOR signal peptide by an authentic E. coli Tat signal peptide, which is derived from pre-trimethylamine N-oxide (TMAO) reductase (TorA), allowed export of GFOR, together with its bound cofactor, to the E. coli periplasm. This export was inhibited by carbonyl cyanide m-chlorophenylhydrazone, but not by sodium azide, and was blocked in E. coli tatC andtatAE mutant strains, showing that membrane translocation of the TorA-GFOR fusion protein occurred via the Tat pathway and not via the Sec pathway. Furthermore, tight cofactor binding (and therefore correct folding) was found to be a prerequisite for proper translocation of the fusion protein. These results strongly suggest that Tat signal peptides are not universally recognized by different Tat translocases, implying that the signal peptides of Tat-dependent precursor proteins are optimally adapted only to their cognate export apparatus. Such a situation is in marked contrast to the situation that is known to exist for Sec-dependent protein translocation.

scholarly journals A twin arginine signal peptide and the pH gradient trigger reversible assembly of the thylakoid ΔpH/Tat translocase

2002 ◽  
Vol 157 (2) ◽  
pp. 205-210 ◽  
Author(s):  
Hiroki Mori ◽  
Kenneth Cline
Keyword(s):  
Signal Peptide ◽  
Protein Translocation ◽  
Permeability Barrier ◽  
Synthetic Signal ◽  
Tat Pathway ◽  
Precursor Proteins ◽  
Varied Size ◽  
Tat System ◽  
Folded Proteins ◽  
Chemical Cross Linking

The thylakoid ΔpH-dependent/Tat pathway is a novel system with the remarkable ability to transport tightly folded precursor proteins using a transmembrane ΔpH as the sole energy source. Three known components of the transport machinery exist in two distinct subcomplexes. A cpTatC–Hcf106 complex serves as precursor receptor and a Tha4 complex is required after precursor recognition. Here we report that Tha4 assembles with cpTatC–Hcf106 during the translocation step. Interactions among components were examined by chemical cross-linking of intact thylakoids followed by immunoprecipitation and immunoblotting. cpTatC and Hcf106 were consistently associated under all conditions tested. In contrast, Tha4 was only associated with cpTatC and Hcf106 in the presence of a functional precursor and the ΔpH. Interestingly, a synthetic signal peptide could replace intact precursor in triggering assembly. The association of all three components was transient and dissipated upon the completion of protein translocation. Such an assembly–disassembly cycle could explain how the ΔpH/Tat system can assemble translocases to accommodate folded proteins of varied size. It also explains in part how the system can exist in the membrane without compromising its ion and proton permeability barrier.

scholarly journals The ER-associated protease Ste24 prevents N-terminal signal peptide-independent translocation into the endoplasmic reticulum in Saccharomyces cerevisiae

2020 ◽  
Vol 295 (30) ◽  
pp. 10406-10419 ◽  
Author(s):  
Akira Hosomi ◽  
Kazuko Iida ◽  
Toshihiko Cho ◽  
Hidetoshi Iida ◽  
Masashi Kaneko ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Endoplasmic Reticulum ◽  
Transcription Factor ◽  
Signal Peptide ◽  
Secretory Pathway ◽  
Soluble Proteins ◽  
Signal Peptides ◽  
Yeast Mutant ◽  
The Past ◽  
Reporter Proteins

Soluble proteins destined for the secretory pathway contain an N-terminal signal peptide that induces their translocation into the endoplasmic reticulum (ER). The importance of N-terminal signal peptides for ER translocation has been extensively examined over the past few decades. However, in the budding yeast Saccharomyces cerevisiae, a few proteins devoid of a signal peptide are still translocated into the ER and then N-glycosyl-ated. Using signal peptide-truncated reporter proteins, here we report the detection of significant translocation of N-terminal signal peptide-truncated proteins in a yeast mutant strain (ste24Δ) that lacks the endopeptidase Ste24 at the ER membrane. Furthermore, several ER/cytosolic proteins, including Sec61, Sec66, and Sec72, were identified as being involved in the translocation process. On the basis of screening for 20 soluble proteins that may be N-glycosylated in the ER in the ste24Δ strain, we identified the transcription factor Rme1 as a protein that is partially N-glycosylated despite the lack of a signal peptide. These results clearly indicate that some proteins lacking a signal peptide can be translocated into the ER and that Ste24 typically suppresses this process.

scholarly journals A signal sequence suppressor mutant that stabilizes an assembled state of the twin arginine translocase

2017 ◽  
Vol 114 (10) ◽  
pp. E1958-E1967 ◽  
Author(s):  
Qi Huang ◽  
Felicity Alcock ◽  
Holger Kneuper ◽  
Justin C. Deme ◽  
Sarah E. Rollauer ◽  
...  
Keyword(s):  
Signal Peptide ◽  
Protein Translocation ◽  
Signal Sequence ◽  
Transmembrane Helix ◽  
Peptide Binding ◽  
Signal Peptides ◽  
Arginine Residues ◽  
Tat System ◽  
Twin Arginine Translocase

The twin-arginine protein translocation (Tat) system mediates transport of folded proteins across the cytoplasmic membrane of bacteria and the thylakoid membrane of chloroplasts. The Tat system ofEscherichia coliis made up of TatA, TatB, and TatC components. TatBC comprise the substrate receptor complex, and active Tat translocases are formed by the substrate-induced association of TatA oligomers with this receptor. Proteins are targeted to TatBC by signal peptides containing an essential pair of arginine residues. We isolated substitutions, locating to the transmembrane helix of TatB that restored transport activity to Tat signal peptides with inactivating twin arginine substitutions. A subset of these variants also suppressed inactivating substitutions in the signal peptide binding site on TatC. The suppressors did not function by restoring detectable signal peptide binding to the TatBC complex. Instead, site-specific cross-linking experiments indicate that the suppressor substitutions induce conformational change in the complex and movement of the TatB subunit. The TatB F13Y substitution was associated with the strongest suppressing activity, even allowing transport of a Tat substrate lacking a signal peptide. In vivo analysis using a TatA–YFP fusion showed that the TatB F13Y substitution resulted in signal peptide-independent assembly of the Tat translocase. We conclude that Tat signal peptides play roles in substrate targeting and in triggering assembly of the active translocase.

scholarly journals Functional Analysis of the Twin-Arginine Translocation Pathway in Corynebacterium glutamicum ATCC 13869

2006 ◽  
Vol 72 (11) ◽  
pp. 7183-7192 ◽  
Author(s):  
Yoshimi Kikuchi ◽  
Masayo Date ◽  
Hiroshi Itaya ◽  
Kazuhiko Matsui ◽  
Long-Fei Wu
Keyword(s):  
Corynebacterium Glutamicum ◽  
Signal Peptide ◽  
Fluorescent Protein ◽  
Peptide Sequence ◽  
Signal Peptide Sequence ◽  
Gram Negative ◽  
Tat Pathway ◽  
Tat System ◽  
Folded Proteins ◽  
Green Fluorescent

ABSTRACT Compared to those of other gram-positive bacteria, the genetic structure of the Corynebacterium glutamicum Tat system is unique in that it contains the tatE gene in addition to tatA, tatB, and tatC. The tatE homologue has been detected only in the genomes of gram-negative enterobacteria. To assess the function of the C. glutamicum Tat pathway, we cloned the tatA, tatB, tatC, and tatE genes from C. glutamicum ATCC 13869 and constructed mutants carrying deletions of each tat gene or of both the tatA and tatE genes. Using green fluorescent protein (GFP) fused with the twin-arginine signal peptide of the Escherichia coli TorA protein, we demonstrated that the minimal functional Tat system required TatA and TatC. TatA and TatE provide overlapping function. Unlike the TatB proteins from gram-negative bacteria, C. glutamicum TatB was dispensable for Tat function, although it was required for maximal efficiency of secretion. The signal peptide sequence of the isomaltodextranase (IMD) of Arthrobacter globiformis contains a twin-arginine motif. We showed that both IMD and GFP fused with the signal peptide of IMD were secreted via the C. glutamicum Tat pathway. These observations indicate that IMD is a bona fide Tat substrate and imply great potential of the C. glutamicum Tat system for industrial production of heterologous folded proteins.

scholarly journals Substrate-gated docking of pore subunit Tha4 in the TatC cavity initiates Tat translocase assembly

2014 ◽  
Vol 205 (1) ◽  
pp. 51-65 ◽  
Author(s):  
Cassie Aldridge ◽  
Xianyue Ma ◽  
Fabien Gerard ◽  
Kenneth Cline
Keyword(s):  
Signal Peptide ◽  
Receptor Complex ◽  
Core Component ◽  
The Core ◽  
Contact Sites ◽  
Contact Data ◽  
Folded Proteins ◽  
Twin Arginine Translocase ◽  
Enclosed Chamber

The twin-arginine translocase (Tat) transports folded proteins across tightly sealed membranes. cpTatC is the core component of the thylakoid translocase and coordinates transport through interactions with the substrate signal peptide and other Tat components, notably the Tha4 pore-forming component. Here, Cys–Cys matching mapped Tha4 contact sites on cpTatC and assessed the role of signal peptide binding on Tha4 assembly with the cpTatC–Hcf106 receptor complex. Tha4 made contact with a peripheral cpTatC site in nonstimulated membranes. In the translocase, Tha4 made an additional contact within the cup-shaped cavity of cpTatC that likely seeds Tha4 polymerization to form the pore. Substrate binding triggers assembly of Tha4 onto the interior site. We provide evidence that the substrate signal peptide inserts between cpTatC subunits arranged in a manner that conceivably forms an enclosed chamber. The location of the inserted signal peptide and the Tha4–cpTatC contact data suggest a model for signal peptide–gated Tha4 entry into the chamber to form the translocase.

scholarly journals Engineering of The Bacillus Subtilis PhoD Signal Peptide To Direct High-Level, Tat-Specific Export of A Single-Chain Antibody Fragment To The Periplasm in Eschericha Coli

2020 ◽  
Author(s):  
Chillel Jawara ◽  
Kirsty L Richards ◽  
Amber R Peswani ◽  
Kelly L Walker ◽  
Lara Nascimento ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Signal Peptide ◽  
Antibody Fragment ◽  
Signal Peptides ◽  
Heterologous Proteins ◽  
Single Chain ◽  
Single Chain Antibody ◽  
E Coli ◽  
Tat Pathway ◽  
Single Chain Antibody Fragment

Abstract Background: Numerous high-value proteins have been produced in E. coli, and a favoured strategy is to export the protein of interest to the periplasm by means of an N-terminal signal peptide. While the Sec pathway has been extensively used for this purpose, the Tat pathway has potential because it transports fully-folded heterologous proteins. Most studies on the Tat pathway have used the E. coli TorA signal peptide to direct export, because it is highly Tat-specific, unlike many Tat signal peptides which can also function as Sec signal peptides. However, the TorA signal peptide is prone to degradation in the cytoplasm, leading to reduced export rates in some cases. Here, we have tested a range of alternative signal peptides for their ability to direct Tat-dependent export of a single-chain antibody fragment (scFv). Results: We show that the signal peptides of E. coli AmiC, MdoD and YcbK direct efficient export of the scFv by both the Tat and Sec pathways, which may be a disadvantage when Tat-specific export is required. The same applies to the Tat signal peptide of Bacillus subtilis PhoD, which likewise directs efficient export by Sec. We engineered the PhoD signal peptide by introduction of a Lys or Asn residue in the C-terminal domain of the signal peptide, and we show that this substitution renders the signal peptide Tat-specific. These signal peptides, designated PhoDk and PhoDn, direct efficient export of scFv in shake flask and fed-batch fermentation studies, reaching export levels that are well above those obtained with the TorA signal peptide. Culturing in ambr250 bioreactors was used to fine-tune the growth conditions, and the net result was export of the scFv by the Tat pathway at levels of approximately 1g protein/L culture. Conclusions: The new PhoDn and PhoDk signal peptides have significant potential for the export of heterologous proteins by the Tat system.

scholarly journals Twin-Arginine Translocation Pathway inStreptomyces lividans

2001 ◽  
Vol 183 (23) ◽  
pp. 6727-6732 ◽  
Author(s):  
Kristien Schaerlaekens ◽  
Michaela Schierová ◽  
Elke Lammertyn ◽  
Nick Geukens ◽  
Jozef Anné ◽  
...  
Keyword(s):  
Signal Peptide ◽  
Streptomyces Antibioticus ◽  
E Coli ◽  
Twin Arginine Translocation ◽  
Tat Pathway ◽  
Chimeric Construct ◽  
Translocation Pathway ◽  
Folded Proteins ◽  
Subtilisin Inhibitor ◽  
Dependent Transport

ABSTRACT The recently discovered bacterial twin-arginine translocation (Tat) pathway was investigated in Streptomyces lividans, a gram-positive organism with a high secretion capacity. The presence of one tatC and two hcf106 homologs in theS. lividans genome together with the several precursor proteins with a twin-arginine motif in their signal peptide suggested the presence of the twin-arginine translocation pathway in the S. lividans secretome. To demonstrate its functionality, atatC deletion mutant was constructed. This mutation impaired the translocation of the Streptomyces antibioticustyrosinase, a protein that forms a complex with its transactivator protein before export. Also the chimeric construct pre-TorA-23K, known to be exclusively secreted via the Tat pathway in Escherichia coli, could be translocated in wild-type S. lividansbut not in the tatC mutant. In contrast, the secretion of the Sec-dependent S. lividans subtilisin inhibitor was not affected. This study therefore demonstrates that also in general inStreptomyces spp. the Tat pathway is functional. Moreover, this Tat pathway can translocate folded proteins, and the E. coli TorA signal peptide can direct Tat-dependent transport in S. lividans.

scholarly journals The Canonical Twin-Arginine Translocase Components Are Not Required for Secretion of Folded Green Fluorescent Protein from the Ancestral Strain of Bacillus subtilis

2014 ◽  
Vol 80 (10) ◽  
pp. 3219-3232 ◽  
Author(s):  
Anthony J. Snyder ◽  
Sampriti Mukherjee ◽  
J. Kyle Glass ◽  
Daniel B. Kearns ◽  
Suchetana Mukhopadhyay
Keyword(s):  
Bacillus Subtilis ◽  
Green Fluorescent Protein ◽  
Signal Peptide ◽  
Secretory Pathway ◽  
Fluorescent Protein ◽  
Secretion Systems ◽  
Content Type ◽  
Twin Arginine Translocase ◽  
Green Fluorescent ◽  
Ancestral Strain

ABSTRACTCellular processes, such as the digestion of macromolecules, phosphate acquisition, and cell motility, require bacterial secretion systems. InBacillus subtilis, the predominant protein export pathways are Sec (generalized secretory pathway) and Tat (twin-arginine translocase). Unlike Sec, which secretes unfolded proteins, the Tat machinery secretes fully folded proteins across the plasma membrane and into the medium. Proteins are directed for Tat-dependent export by N-terminal signal peptides that contain a conserved twin-arginine motif. Thus, utilizing the Tat secretion system by fusing a Tat signal peptide is an attractive strategy for the production and export of heterologous proteins. As a proof of concept, we expressed green fluorescent protein (GFP) fused to the PhoD Tat signal peptide in the laboratory and ancestral strains ofB. subtilis. Secretion of the Tat-GFP construct, as well as secretion of proteins in general, was substantially increased in the ancestral strain. Furthermore, our results show that secreted, fluorescent GFP could be purified directly from the extracellular medium. Nonetheless, export was not dependent on the known Tat secretion components or the signal peptide twin-arginine motif. We propose that the ancestral strain contains additional Tat components and/or secretion regulators that were abrogated following domestication.

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