The structural basis of autotransporter translocation by TamA

Gruss, Fabian; Zähringer, Franziska; Jakob, R.P.; Burmann, Björn M.; Hiller, Sebastian; Maier, Timm

doi:10.1038/nsmb.2689

Cited by 120 publications

(188 citation statements)

References 31 publications

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“…Although structures have been reported for the orthologs of the Omp85 family, including FhaC, TamA, and BamA, in Gram-negative bacteria (35,36,(43)(44)(45)(46), no structure has been reported for either Sam50 in mitochondria or Toc75 or OEP80 in chloroplasts. Here we report the structure of Toc75, from A. thaliana, consisting of the N-terminal linker and three tandem POTRA domains (Figs.…”

Section: Discussionmentioning

confidence: 99%

“…Indicated amounts of purified POTRAs diluted in HMK buffer to an imidazole concentration of ∼10 mM or less was immobilized on 10 μL of packed Ni-NTA His-Bind resin (Novagen) for 2 h at room temperature. Resin was washed once with HMK buffer with 10 mM imidazole and 0.1% Triton X-100 (HMKIT) or, in the case of [ 35 S]DHFR) was added to immobilized POTRAs at equimolar amounts, determined by correcting the IVT signal of each substrate for the number of methionine residues and its relative molecular weight. Between 1 and 5 μL of IVT was added to each reaction (i.e., 5 μL of [ 35 S]SSU was used and ∼1-3 μL of other substrates were used depending on their corrected IVT signal).…”

Section: Sec-saxsmentioning

confidence: 99%

“…The structure reveals that the POTRA domains form an L-shaped structure very similar to BamA, with a unique extended helix within POTRA2 that is not observed in the POTRA domains of BamA and other Omp85 family members (25,28,(35)(36)(37)(38). Based on these unique structural properties, we investigated the contribution of individual POTRA repeats in binding chloroplast precursors.…”

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confidence: 99%

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The POTRA domains of Toc75 exhibit chaperone-like function to facilitate import into chloroplasts

O'Neil

Richardson

Paila

et al. 2017

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

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Protein trafficking across membranes is an essential function in cells; however, the exact mechanism for how this occurs is not well understood. In the endosymbionts, mitochondria and chloroplasts, the vast majority of proteins are synthesized in the cytoplasm as preproteins and then imported into the organelles via specialized machineries. In chloroplasts, protein import is accomplished by the TOC (translocon on the outer chloroplast membrane) and TIC (translocon on the inner chloroplast membrane) machineries in the outer and inner envelope membranes, respectively. TOC mediates initial recognition of preproteins at the outer membrane and includes a core membrane channel, Toc75, and two receptor proteins, Toc33/34 and Toc159, each containing GTPase domains that control preprotein binding and translocation. Toc75 is predicted to have a β-barrel fold consisting of an N-terminal intermembrane space (IMS) domain and a C-terminal 16-stranded β-barrel domain. Here we report the crystal structure of the N-terminal IMS domain of Toc75 from Arabidopsis thaliana, revealing three tandem polypeptide transportassociated (POTRA) domains, with POTRA2 containing an additional elongated helix not observed previously in other POTRA domains. Functional studies show an interaction with the preprotein, preSSU, which is mediated through POTRA2-3. POTRA2-3 also was found to have chaperone-like activity in an insulin aggregation assay, which we propose facilitates preprotein import. Our data suggest a model in which the POTRA domains serve as a binding site for the preprotein as it emerges from the Toc75 channel and provide a chaperonelike activity to prevent misfolding or aggregation as the preprotein traverses the intermembrane space.protein import | chloroplast | outer membrane | Toc75 | POTRA domain

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Section: Discussionmentioning

confidence: 99%

Section: Sec-saxsmentioning

confidence: 99%

mentioning

confidence: 99%

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The POTRA domains of Toc75 exhibit chaperone-like function to facilitate import into chloroplasts

O'Neil

Richardson

Paila

et al. 2017

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

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“…Regardless of whether this channel is formed by the AT ␤-barrel domain alone or is held open and/or complemented by chaperones like BamA or TamA (14,46,47), entering this constrained space represents an energetically unfavorable confinement of the passenger (Fig. 9).…”

Section: Discussionmentioning

confidence: 99%

Multiple Driving Forces Required for Efficient Secretion of Autotransporter Virulence Proteins

Drobnak¹,

Braselmann²,

Clark

2015

Journal of Biological Chemistry

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Background: Many virulence proteins are secreted using the autotransporter system. Results: Autotransporter proteins do not fold until secreted and are secreted poorly in the absence of folding. Conclusion: Folding helps drive autotransporter secretion, but another energy source is required for its initiation. Significance: Our conclusions reconcile apparent contradictions in the literature and importantly contribute to understanding and manipulating autotransporter secretion.

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“…Even if this does not involve a local gelto-liquid membrane structure, uOMP intrinsic folding kinetics clearly show that any inhomogeneity in lipid packing represents a membrane structure that accelerates uOMP folding. BamA is well suited to create them, and it is important to note that BamA stabilization of excited lipid structures is not necessarily mutually exclusive to other proposed models for how BamA functions, such as lateral gate opening [40] and/or templating of a budding baby barrel [42].…”

Section: Introduction: the Challenges Of Unfolded Outer Membrane Protmentioning

confidence: 99%

A combined kinetic push and thermodynamic pull as driving forces for outer membrane protein sorting and folding in bacteria

Fleming

2015

Phil. Trans. R. Soc. B

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One contribution of 12 to a theme issue 'The bacterial cell envelope'. In vitro folding studies of outer membrane beta-barrels have been invaluable in revealing the lipid effects on folding rates and efficiencies as well as folding free energies. Here, the biophysical results are summarized, and these kinetic and thermodynamic findings are considered in terms of the requirements for folding in the context of the cellular environment. Because the periplasm lacks an external energy source the only driving forces for sorting and folding available within this compartment are binding or folding free energies and their associated rates. These values define functions for periplasmic chaperones and suggest a biophysical mechanism for the BAM complex.

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The structural basis of autotransporter translocation by TamA

Cited by 120 publications

References 31 publications

The POTRA domains of Toc75 exhibit chaperone-like function to facilitate import into chloroplasts

The POTRA domains of Toc75 exhibit chaperone-like function to facilitate import into chloroplasts

Multiple Driving Forces Required for Efficient Secretion of Autotransporter Virulence Proteins

A combined kinetic push and thermodynamic pull as driving forces for outer membrane protein sorting and folding in bacteria

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