TatB Functions as an Oligomeric Binding Site for Folded Tat Precursor Proteins

Maurer, H. Carlo; Panahandeh, Sascha; Jungkamp, Anna-Carina; Moser, Michael J.; Müller, Matthias

doi:10.1091/mbc.e10-07-0585

Cited by 53 publications

(76 citation statements)

References 60 publications

(105 reference statements)

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“…complexes consisting of one precursor molecule and one TatA monomer only. This is in complete contrast to a previous study on larger complexes between RR precursors and TatB oligomers that were interpreted to suggest encapsulation of a membrane-targeted RR precursor by multiple amphipathic helices of TatB (18). Furthermore, we would have expected that contacts of a translocating Tat substrate with a ring of transmembrane helices of TatA were restricted to the inner surface of the transmembrane helices that face the lumen of the pore.…”

Section: Discussioncontrasting

confidence: 92%

“…Contact sites include the transmembrane and the amphipathic helix of TatA as well as its unstructured C terminus. A previous cross-linking analysis of the interaction of membrane-targeted, folded RR precursor proteins with the TatA homologue TatB revealed extended contacts with the amphipathic helix of TatB (18). We were therefore not surprised to also obtain cross-links between RR precursors and the amphipathic helix of TatA, conceivably reflecting extramembrane contacts with a surface-exposed precursor protein.…”

Section: Discussionmentioning

confidence: 62%

“…1, B and C) did not follow a clear helical pattern suggests that the interacting TatA molecules must be rather flexible at this stage of contact. Moreover, quite different from the binding of RR precursors to TatB (18), no higher molecular mass adducts between the RR precursors and TatA were obtained. Such adducts would be expected to form if an oligomeric TatA structure would allow more than one TatA monomer to bind to a single precursor molecule.…”

Section: Upon Binding To the Tat Translocase Rr Precursors Makementioning

confidence: 72%

“…Plasmid p8737 (51) containing the tatABCD operon under T7 promoter control served as template to introduce the various stop codons into tatA as described (18) using the pairs of forward and reverse primers listed in the supplemental table. Plasmid pSup-BpaRS-6TRN(D86R) (52) encodes a Bpa-tRNA synthetase and a Bpa-specific amber suppressor tRNA.…”

Section: Methodsmentioning

confidence: 99%

“…Control experiments had shown that in these conditions, cross-linking reached its maximum within 7 min. ATP depletion using glucose and hexokinase was performed as described previously (18).…”

Section: Methodsmentioning

confidence: 99%

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Early Contacts between Substrate Proteins and TatA Translocase Component in Twin-arginine Translocation

Fröbel

Rose

Müller

2011

Journal of Biological Chemistry

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Background:The membrane proteins, TatA, TatB, and TatC, enable the transmembrane passage of folded precursor proteins. Results: The transmembrane helix of TatA makes contacts with TatC and precursors recognized by the TatBC complex. Conclusion: Following its insertion into the TatBC receptor complex, a Tat signal sequence contacts a nearby monomer of TatA. Significance: TatA interacts with twin-arginine precursors prior to the actual translocation event.

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Section: Discussioncontrasting

confidence: 92%

Section: Discussionmentioning

confidence: 62%

Section: Upon Binding To the Tat Translocase Rr Precursors Makementioning

confidence: 72%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Early Contacts between Substrate Proteins and TatA Translocase Component in Twin-arginine Translocation

Fröbel

Rose

Müller

2011

Journal of Biological Chemistry

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Thylakoid‐integrated recombinant Hcf106 participates in the chloroplast twin arginine transport system

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New

et al. 2018

Plant Direct

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The chloroplast twin arginine transport (cpTat) system distinguishes itself as a protein transport pathway by translocating fully folded proteins, using the proton‐motive force (PMF) as the sole source of energy. The cpTat pathway is evolutionarily conserved with the Tat pathway found in the plasma membrane of many prokaryotes. The cpTat (Escherichia coli) system uses three proteins, Tha4 (TatA), Hcf106 (TatB), and cpTatC (TatC), to form a transient translocase allowing the passage of precursor proteins. Briefly, cpTatC and Hcf106, with Tha4, form the initial receptor complex responsible for precursor protein recognition and binding in an energy‐independent manner, while a separate pool of Tha4 assembles with the precursor‐bound receptor complex in the presence the PMF. Analysis by blue‐native polyacrylamide gel electrophoresis (BN‐PAGE) shows that the receptor complex, in the absence of precursor, migrates near 700 kDa and contains cpTatC and Hcf106 with little Tha4 remaining after detergent solubilization. To investigate the role that Hcf106 may play in receptor complex oligomerization and/or stability, systematic cysteine substitutions were made in positions from the N‐terminal transmembrane domain to the end of the predicted amphipathic helix of the protein. BN‐PAGE analysis allowed us to identify the locations of amino acids in Hcf106 that were critical for interacting with cpTatC. Oxidative cross‐linking allowed us to map interactions of the transmembrane domain and amphipathic helix region of Hcf106. In addition, we showed that in vitro expressed, integrated Hcf106 can interact with the precursor signal peptide domain and imported cpTatC, strongly suggesting that a subpopulation of the integrated Hcf106 is participating in competent cpTat complexes.

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Transport of Folded Proteins by the Tat System

2019

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The twin-arginine protein translocation (Tat) system has been characterized in bacteria, archaea and the chloroplast thylakoidal membrane. This system is distinct from other protein transport systems with respect to two key features. Firstly, it accepts cargo proteins with an N-terminal signal peptide that carries the canonical twin-arginine motif, which is essential for transport. Second, the Tat system only accepts and translocates fully folded cargo proteins across the respective membrane. Here, we review the core essential features of folded protein transport via the bacterial Tat system, using the three-component TatABC system of Escherichia coli and the two-component TatAC systems of Bacillus subtilis as the main examples. In particular, we address features of twin-arginine signal peptides, the essential Tat components and how they assemble into different complexes, mechanistic features and energetics of Tat-dependent protein translocation, cytoplasmic chaperoning of Tat cargo proteins, and the remarkable proofreading capabilities of the Tat system. In doing so, we present the current state of our understanding of Tat-dependent protein translocation across biological membranes, which may serve as a lead for future investigations.

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TatB Functions as an Oligomeric Binding Site for Folded Tat Precursor Proteins

Cited by 53 publications

References 60 publications

Early Contacts between Substrate Proteins and TatA Translocase Component in Twin-arginine Translocation

Early Contacts between Substrate Proteins and TatA Translocase Component in Twin-arginine Translocation

Thylakoid‐integrated recombinant Hcf106 participates in the chloroplast twin arginine transport system

Transport of Folded Proteins by the Tat System

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