The twin-arginine transport system: moving folded proteins across membranes

2007 ◽  
Vol 35 (5) ◽  
pp. 835-847 ◽  
Author(s):  
F. Sargent
Keyword(s):  
Protein Targeting ◽  
Plant Mitochondria ◽  
Global Scale ◽  
Signal Peptides ◽  
Amino Acid Motif ◽  
Transport Pathway ◽  
Arginine Transport ◽  
Cytoplasmic Membranes ◽  
Genes Encoding ◽  
Folded Proteins

The Tat (twin-arginine transport) pathway is a protein-targeting system dedicated to the transmembrane translocation of fully folded proteins. This system is highly prevalent in the cytoplasmic membranes of bacteria and archaea, and is also found in the thylakoid membranes of plant chloroplasts and possibly also in the inner membrane of plant mitochondria. Proteins are targeted to a membrane-embedded Tat translocase by specialized N-terminal twin-arginine signal peptides bearing an SRRXFLK amino acid motif. The genes encoding components of the Tat translocase were discovered approx. 10 years ago, and, since then, research in this area has expanded on a global scale. In this review, the key discoveries in this field are summarized, and recent studies of bacterial twin-arginine signal-peptide-binding proteins are discussed.

Common principles in the biosynthesis of diverse enzymes

2005 ◽  
Vol 33 (1) ◽  
pp. 105-107 ◽  
Author(s):  
R.L. Jack ◽  
A. Dubini ◽  
T. Palmer ◽  
F. Sargent
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Signal Peptides ◽  
Amino Acid Motif ◽  
Dmso Reductase ◽  
Arginine Transport

A subset of bacterial periplasmic enzymes are transported from the cytoplasm by the twin-arginine transport apparatus. Such proteins contain distinctive N-terminal signal peptides containing a conserved SRRXFLK ‘twin-arginine’ amino acid motif and often bind complex cofactors before the transport event. It is important that assembly of complex cofactor-containing, and often multi-subunit, enzymes is complete before export. Studies of the unrelated [NiFe] hydrogenase, DMSO reductase and trimethylamine N-oxide reductase systems from Escherichia coli have enabled us to define a chaperone-mediated ‘proofreading’ mechanism involved in co-ordinating assembly and export of twin-arginine transport-dependent enzymes.

scholarly journals Remnant signal peptides on non-exported enzymes: implications for the evolution of prokaryotic respiratory chains

Microbiology ◽  
2009 ◽  
Vol 155 (12) ◽  
pp. 3992-4004 ◽  
Author(s):  
Bérengère Ize ◽  
Sarah J. Coulthurst ◽  
Kostas Hatzixanthis ◽  
Isabelle Caldelari ◽  
Grant Buchanan ◽  
...  
Keyword(s):  
Amino Acid ◽  
Protein Targeting ◽  
Sequence Similarity ◽  
Molybdenum Cofactor ◽  
Signal Peptides ◽  
Transport Activity ◽  
Respiratory Enzymes ◽  
Folded Proteins ◽  
Prokaryotic Protein

The twin-arginine translocation (Tat) pathway is a prokaryotic protein targeting system dedicated to the transmembrane translocation of folded proteins. Substrate proteins are directed to the Tat translocase by signal peptides bearing a conserved SRRxFLK ‘twin-arginine’ motif. In Escherichia coli, most of the 27 periplasmically located Tat substrates are cofactor-containing respiratory enzymes, and many of these harbour a molybdenum cofactor at their active site. Molybdenum cofactor-containing proteins are not exclusively located in the periplasm, however, with the major respiratory nitrate reductase (NarG) and the biotin sulfoxide reductase (BisC), for example, being located at the cytoplasmic side of the membrane. Interestingly, both NarG and BisC contain ‘N-tail’ regions that bear some sequence similarity to twin-arginine signal peptides. In this work, we have examined the relationship between the non-exported N-tails and the Tat system. Using a sensitive genetic screen for Tat transport, variant N-tails were identified that displayed Tat transport activity. For the NarG 36-residue N-tail, six amino acid changes were needed to induce transport activity. However, these changes interfered with binding by the NarJ biosynthetic chaperone and impaired biosynthesis of the native enzyme. For the BisC 36-residue N-tail, only five amino acid substitutions were needed to restore Tat transport activity. These modifications also impaired in vivo BisC activity, but it was not possible to identify a biosynthetic chaperone for this enzyme. These data highlight an intimate genetic and evolutionary link between some non-exported redox enzymes and those transported across membranes by the Tat translocation system.

scholarly journals Twin-arginine-dependent translocation of folded proteins

2012 ◽  
Vol 367 (1592) ◽  
pp. 1029-1046 ◽  
Author(s):  
Julia Fröbel ◽  
Patrick Rose ◽  
Matthias Müller
Keyword(s):  
Protein Transport ◽  
Signal Sequence ◽  
Transmembrane Protein ◽  
Proton Motive Force ◽  
Signal Peptides ◽  
Transport Pathway ◽  
Twin Arginine Translocation ◽  
Precursor Proteins ◽  
Binding Pockets ◽  
Folded Proteins

Twin-arginine translocation (Tat) denotes a protein transport pathway in bacteria, archaea and plant chloroplasts, which is specific for precursor proteins harbouring a characteristic twin-arginine pair in their signal sequences. Many Tat substrates receive cofactors and fold prior to translocation. For a subset of them, proofreading chaperones coordinate maturation and membrane-targeting. Tat translocases comprise two kinds of membrane proteins, a hexahelical TatC-type protein and one or two members of the single-spanning TatA protein family, called TatA and TatB. TatC- and TatA-type proteins form homo- and hetero-oligomeric complexes. The subunits of TatABC translocases are predominantly recovered from two separate complexes, a TatBC complex that might contain some TatA, and a homomeric TatA complex. TatB and TatC coordinately recognize twin-arginine signal peptides and accommodate them in membrane-embedded binding pockets. Advanced binding of the signal sequence to the Tat translocase requires the proton-motive force (PMF) across the membranes and might involve a first recruitment of TatA. When targeted in this manner, folded twin-arginine precursors induce homo-oligomerization of TatB and TatA. Ultimately, this leads to the formation of a transmembrane protein conduit that possibly consists of a pore-like TatA structure. The translocation step again is dependent on the PMF.

scholarly journals Characterization of a pre-export enzyme–chaperone complex on the twin-arginine transport pathway

2013 ◽  
Vol 452 (1) ◽  
pp. 57-66 ◽  
Author(s):  
Jennifer M. Dow ◽  
Frank Gabel ◽  
Frank Sargent ◽  
Tracy Palmer
Keyword(s):  
Signal Peptide ◽  
Protein Targeting ◽  
Transport Pathway ◽  
X Ray ◽  
Twin Arginine Translocation ◽  
X Ray Scattering ◽  
Biophysical Techniques ◽  
Folded Proteins ◽  
Chaperone Complex

The Tat (twin-arginine translocation) system is a protein targeting pathway utilized by prokaryotes and chloroplasts. Tat substrates are produced with distinctive N-terminal signal peptides and are translocated as fully folded proteins. In Escherichia coli, Tat-dependent proteins often contain redox cofactors that must be loaded before translocation. Trimethylamine N-oxide reductase (TorA) is a model bacterial Tat substrate and is a molybdenum cofactor-dependent enzyme. Co-ordination of cofactor loading and translocation of TorA is directed by the TorD protein, which is a cytoplasmic chaperone known to interact physically with the TorA signal peptide. In the present study, a pre-export TorAD complex has been characterized using biochemical and biophysical techniques, including SAXS (small-angle X-ray scattering). A stable, cofactor-free TorAD complex was isolated, which revealed a 1:1 binding stoichiometry. Surprisingly, a TorAD complex with similar architecture can be isolated in the complete absence of the 39-residue TorA signal peptide. The present study demonstrates that two high-affinity binding sites for TorD are present on TorA, and that a single TorD protein binds both of those simultaneously. Further characterization suggested that the C-terminal ‘Domain IV’ of TorA remained solvent-exposed in the cofactor-free pre-export TorAD complex. It is possible that correct folding of Domain IV upon cofactor loading is the trigger for TorD release and subsequent export of TorA.

Identification of four nuclear transport signal-binding proteins that interact with diverse transport signals

1989 ◽  
Vol 9 (7) ◽  
pp. 3028-3036
Author(s):  
L Yamasaki ◽  
P Kanda ◽  
R E Lanford
Keyword(s):  
Binding Proteins ◽  
Nuclear Transport ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Nuclear Pore ◽  
Signal Peptides ◽  
Signal Recognition ◽  
Transport Pathway

The transport of proteins into the nucleus requires not only the presence of a nuclear transport signal on the targeted protein but also the signal recognition proteins and the nuclear pore translocation apparatus. Complicating the search for the signal recognition proteins is the fact that the nuclear transport signals identified share little obvious homology. In this study, synthetic peptides homologous to the nuclear transport signals from the simian virus 40 large T antigen, Xenopus oocyte nucleoplasmin, adenovirus E1A, and Saccharomyces cerevisiae MAT alpha 2 proteins were coupled to a UV-photoactivable cross-linker and iodinated for use in an in vitro cross-linking reaction with cellular lysates. Four proteins, p140, p100, p70, and p55, which specifically interacted with the nuclear transport signal peptides were identified. Unique patterns of reactivity were observed with closely related pairs of nuclear transport signal peptides. Competition experiments with labeled and unlabeled peptides demonstrated that heterologous signals were able to bind the same protein and suggested that diverse signals use a common transport pathway. The subcellular distribution of the four nuclear transport signal-binding proteins suggested that nuclear transport involves both cytoplasmic and nuclear receptors. The four proteins were not bound by wheat germ agglutinin and were not associated tightly with the nuclear pore complex.

Optimization of Yarrowia lipolytica-based consolidated biocatalyst through synthetic biology approach: transcription units and signal peptides shuffling

2020 ◽  
Author(s):  
Ewelina Celińska ◽  
Monika Borkowska ◽  
Paulina Korpys-Woźniak ◽  
Monika Kubiak ◽  
Jean-Marc Nicaud ◽  
...  
Keyword(s):  
Gene Copy Number ◽  
Regulatory Elements ◽  
Gene Copy ◽  
Signal Peptides ◽  
Synthetic Dna ◽  
Batch Bioreactor ◽  
Genes Encoding ◽  
Valuable Compounds ◽  
Synthetic Biology Approach ◽  
Lipids Accumulation

Abstract Background: Nowadays considerable effort is being pursued towards development of consolidated microbial biocatalysts that will be able to utilize complex, non-pretreated substrates and produce valuable compounds. In such engineered microbes, synthesis of extracellular hydrolases may be fine-tuned by different approaches, like strength of promoter, type of secretory tag, gene copy number etc. In this study, we investigated if organization of a multi-element expression cassette impacts the resultant Y. lipolytica transformants’ phenotype, presuming that different variants of the cassette are composed of the same regulatory elements and encode the same hydrolases. Results: To this end, Y. lipolytica cells were transformed with expression cassettes bearing a pair of genes encoding exactly the same mature amylases, but fused to four different signal peptides (SP), and located interchangeably in either first or second position of a synthetic DNA construction. The resultant strains were tested for growth on raw and pre-treated complex substrates of different plant origin for comprehensive examination of the strains’ acquired characteristics. The best strain’s performance was tested in batch bioreactor cultivations for growth and lipids accumulation. Conclusions: Based on the conducted research we concluded that the positional order of transcription units (TU) and the type of exploited SP affect final characteristics of the resultant consolidated biocatalyst strains, and thus could be considered as additional factors to be evaluated upon consolidated biocatalysts optimization.

scholarly journals Transcriptomic Profiling Identifies Candidate Genes Involved in the Salt Tolerance of the Xerophyte Pugionium cornutum

Genes ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 1039 ◽  
Author(s):  
Yan-Nong Cui ◽  
Fang-Zhen Wang ◽  
Cheng-Hang Yang ◽  
Jian-Zhen Yuan ◽  
Huan Guo ◽  
...  
Keyword(s):  
Salt Stress ◽  
Salt Tolerance ◽  
Candidate Genes ◽  
Osmotic Adjustment ◽  
Assimilation Efficiency ◽  
Carbon Assimilation ◽  
Ros Scavenging ◽  
Transport Pathway ◽  
Genes Encoding ◽  
Assimilation Capacity

The xerophyte Pugionium cornutum adapts to salt stress by accumulating inorganic ions (e.g., Cl−) for osmotic adjustment and enhancing the activity of antioxidant enzymes, but the associated molecular basis remains unclear. In this study, we first found that P. cornutum could also maintain cell membrane stability due to its prominent ROS-scavenging ability and exhibits efficient carbon assimilation capacity under salt stress. Then, the candidate genes associated with the important physiological traits of the salt tolerance of P. cornutum were identified through transcriptomic analysis. The results showed that after 50 mM NaCl treatment for 6 or 24 h, multiple genes encoding proteins facilitating Cl− accumulation and NO3− homeostasis, as well as the transport of other major inorganic osmoticums, were significantly upregulated in roots and shoots, which should be favorable for enhancing osmotic adjustment capacity and maintaining the uptake and transport of nutrient elements; a large number of genes related to ROS-scavenging pathways were also significantly upregulated, which might be beneficial for mitigating salt-induced oxidative damage to the cells. Meanwhile, many genes encoding components of the photosynthetic electron transport pathway and carbon fixation enzymes were significantly upregulated in shoots, possibly resulting in high carbon assimilation efficiency in P. cornutum. Additionally, numerous salt-inducible transcription factor genes that probably regulate the abovementioned processes were found. This work lays a preliminary foundation for clarifying the molecular mechanism underlying the adaptation of xerophytes to harsh environments.

scholarly journals Characterization of the Accessory Sec System of Staphylococcus aureus

2008 ◽  
Vol 190 (18) ◽  
pp. 6188-6196 ◽  
Author(s):  
Ian R. Siboo ◽  
Donald O. Chaffin ◽  
Craig E. Rubens ◽  
Paul M. Sullam
Keyword(s):  
Staphylococcus Aureus ◽  
Surface Expression ◽  
Complete Loss ◽  
Transport Pathway ◽  
Gram Positive Bacteria ◽  
Difference Gel Electrophoresis ◽  
Genes Encoding ◽  
Sec System ◽  
Specialized System

ABSTRACT The SraP adhesin of Staphylococcus aureus is a member of a highly conserved family of serine-rich surface glycoproteins of gram-positive bacteria. For streptococci, export of the SraP homologs requires a specialized transport pathway (the accessory Sec system). Compared to streptococci, however, SraP is predicted to differ in its signal peptide and glycosylation, which may affect its dependence on a specialized system for transport. In addition, two genes (asp4 and asp5) essential for export in Streptococcus gordonii are missing in S. aureus. Thus, the selectivity of the accessory Sec system in S. aureus may also differ compared to streptococci. To address these issues, the five genes encoding the putative accessory Sec system (secY2, secA2, and asp1-3) were disrupted individually in S. aureus ISP479C, and the resultant mutants were examined for SraP export. Disruption of secA2 resulted in the near complete loss of SraP surface expression. Similar results were seen with disruption of secY2 and asp1, asp2, or asp3. To assess whether the accessory Sec system transported other substrates, we compared secreted proteomes of ISP479C and a secA2 isogenic mutant, by two-dimensional fluorescence difference gel electrophoresis. Although two consistent differences in proteome content were noted between the strains, neither protein appeared to be a likely substrate for accessory Sec export. Thus, the accessory Sec system of S. aureus is required for the export of SraP, and it appears to be dedicated to the transport of this substrate exclusively.

scholarly journals Identification of Genes Encoding Exported Mycobacterium tuberculosis Proteins Using a Tn552′phoA In Vitro Transposition System

2000 ◽  
Vol 182 (10) ◽  
pp. 2732-2740 ◽  
Author(s):  
Miriam Braunstein ◽  
Thomas J. Griffin ◽  
Jordan I. Kriakov ◽  
Sarah T. Friedman ◽  
Nigel D. F. Grindley ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Protective Immunity ◽  
Cell Envelope ◽  
Open Reading Frames ◽  
Signal Peptides ◽  
Genomic Libraries ◽  
Target Dna ◽  
Genes Encoding ◽  
Associated Proteins

ABSTRACT Secreted and cell envelope-associated proteins are important to both Mycobacterium tuberculosis pathogenesis and the generation of protective immunity to M. tuberculosis. We used an in vitro Tn552′phoA transposition system to identify exported proteins of M. tuberculosis. The system is simple and efficient, and the transposon inserts randomly into target DNA. M. tuberculosis genomic libraries were targeted with Tn552′phoA transposons, and these libraries were screened in M. smegmatis for active PhoA translational fusions. Thirty-two different M. tuberculosis open reading frames were identified; eight contain standard signal peptides, six contain lipoprotein signal peptides, and seventeen contain one or more transmembrane domains. Four of these proteins had not yet been assigned as exported proteins in the M. tuberculosisdatabases. This collection of exported proteins includes factors that are known to participate in the immune response of M. tuberculosis and proteins with homologies, suggesting a role in pathogenesis. Nine of the proteins appear to be unique to mycobacteria and represent promising candidates for factors that participate in protective immunity and virulence. This technology of creating comprehensive fusion libraries should be applicable to other organisms.

scholarly journals The Tat Substrate SufI Is Critical for the Ability of Yersinia pseudotuberculosis To Cause Systemic Infection

2017 ◽  
Vol 85 (4) ◽  
Author(s):  
Ummehan Avican ◽  
Tugrul Doruk ◽  
Yngve Östberg ◽  
Anna Fahlgren ◽  
Åke Forsberg
Keyword(s):  
Stress Responses ◽  
Pathogenic Bacteria ◽  
Yersinia Pseudotuberculosis ◽  
Systemic Infection ◽  
Mesenteric Lymph Nodes ◽  
Content Type ◽  
Twin Arginine Translocation ◽  
Genes Encoding ◽  
Folded Proteins

ABSTRACT The twin arginine translocation (Tat) system targets folded proteins across the inner membrane and is crucial for virulence in many important human-pathogenic bacteria. Tat has been shown to be required for the virulence of Yersinia pseudotuberculosis, and we recently showed that the system is critical for different virulence-related stress responses as well as for iron uptake. In this study, we wanted to address the role of the Tat substrates in in vivo virulence. Therefore, 22 genes encoding potential Tat substrates were mutated, and each mutant was evaluated in a competitive oral infection of mice. Interestingly, a ΔsufI mutant was essentially as attenuated for virulence as the Tat-deficient strain. We also verified that SufI was Tat dependent for membrane/periplasmic localization in Y. pseudotuberculosis. In vivo bioluminescent imaging of orally infected mice revealed that both the ΔsufI and ΔtatC mutants were able to colonize the cecum and Peyer's patches (PPs) and could spread to the mesenteric lymph nodes (MLNs). Importantly, at this point, neither the ΔtatC mutant nor the ΔsufI mutant was able to spread systemically, and they were gradually cleared. Immunostaining of MLNs revealed that both the ΔtatC and ΔsufI mutants were unable to spread from the initial infection foci and appeared to be contained by neutrophils, while wild-type bacteria readily spread to establish multiple foci from day 3 postinfection. Our results show that SufI alone is required for the establishment of systemic infection and is the major cause of the attenuation of the ΔtatC mutant.

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