Sequence-specific Binding of prePhoD to Soluble TatAd Indicates Protein-mediated Targeting of the Tat Export in Bacillus subtilis

Pop, Ovidiu I.; Westermann, Martin; Volkmer, Rudolf; Schulz, Daniela; Lemke, Cornelius; Schreiber, Sandra; Gerlach, Roman G.; Wetzker, Reinhard; Müller, Jörg P.

doi:10.1074/jbc.m306516200

Cited by 56 publications

(42 citation statements)

References 69 publications

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“…In B. subtilis, cytoplasmic TatA homologs copurify with Tat substrate, suggesting they may be involved in membrane targeting of the precursor (22). Although we have not yet addressed TatA homolog interaction with substrate in Haloferax volcanii, our initial characterization of TatAo and TatAt revealed they stably interact with each other in the cytoplasm.…”

Section: Discussionmentioning

confidence: 88%

“…It was therefore unexpected that TatA homologs were detected in Haloferax volcanii cytoplasmic fractions as well as in cytoplasmic fractions from B. subtilis and Streptomyces lividans (10,22). The presumed role of TatA from work with E. coli has been formation of the translocation channel for the Tat pathway (26).…”

Section: Discussionmentioning

confidence: 99%

“…Further characterization of a B. subtilis TatA homolog demonstrated that this protein (whose E. coli homolog strictly localizes to the inner membrane) is present in both cytoplasmic and membrane fractions. In addition, this cytoplasmic TatA can be copurified with its Tat substrate, alkaline phosphatase (22). With no known general mechanism of membrane targeting of Tat substrates, it is interesting to speculate that B. subtilis TatA homologs are responsible for substrate recognition and targeting.…”

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confidence: 99%

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Genetic and Biochemical Analysis of the Twin-Arginine Translocation Pathway in Halophilic Archaea

2005

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The twin-arginine translocation (Tat) pathway is present in a wide variety of prokaryotes and is capable of exporting partially or fully folded proteins from the cytoplasm. Although diverse classes of proteins are transported via the Tat pathway, in most organisms it facilitates the secretion of a relatively small number of substrates compared to the Sec pathway. However, computational evidence suggests that haloarchaea route nearly all secreted proteins to the Tat pathway. We have expanded previous computational analyses of the haloarchaeal Tat pathway and initiated in vivo characterization of the Tat machinery in a model haloarchaeon, Haloferax volcanii. Consistent with the predicted usage of the this pathway in the haloarchaea, we determined that three of the four identified tat genes in Haloferax volcanii are essential for viability when grown aerobically in complex medium. This represents the first report of an organism that requires the Tat pathway for viability when grown under such conditions. Deletion of the nonessential gene had no effect on the secretion of a verified substrate of the Tat pathway. The two TatA paralogs TatAo and TatAt were detected in both the membrane and cytoplasm and could be copurified from the latter fraction. Using size exclusion chromatography to further characterize cytoplasmic and membrane TatA proteins, we find these proteins present in high-molecularweight complexes in both cellular fractions.

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Section: Discussionmentioning

confidence: 88%

Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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Genetic and Biochemical Analysis of the Twin-Arginine Translocation Pathway in Halophilic Archaea

2005

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“…In addition, because of the co-fractionation of TatA with membranes, which depended on the hydrophobic N-terminal region of the protein, it has been assumed that TatA must be an exclusively membrane-bound component of the Tat system (35). However, electron microscopy of TatA d from Bacillus subtilis revealed that a significant portion of this TatA was present in the cytoplasm where it was able to bind the Tat substrate PhoD (8,26). The TatA d , which interacted with membranes, had substrate bound to it (9).…”

Section: Discussionmentioning

confidence: 99%

Recombinant Expression of tatABC and tatAC Results in the Formation of Interacting Cytoplasmic TatA Tubes in Escherichia coli

Berthelmann

Mehner

Richter

et al. 2008

Journal of Biological Chemistry

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The twin-arginine translocation (Tat) system of bacteria and plant plastids serves to translocate folded proteins across energized biological membranes. In Escherichia coli, the three components TatA, TatB, and TatC mediate this membrane passage. Here we demonstrate that TatA can assemble to form clusters of tube-like structures in vivo. While the presence of TatC is essential for their formation, TatB is not required. The TatA tubes have uniform outer and inner diameters of about 11.5 nm and 6.7 nm, respectively. They align to form a crystalline-like structure in which each tube is surrounded by six TatA tubes. The tube structures become easily detectable even at only a 15-fold overexpression of the tatABC genes. The TatA tubes could also be visualized by fluorescence when untagged TatA was mixed with low amounts of TatA-GFP. The structures were often found in contact with the cell poles. Because TatC is most likely polar in E. coli, as demonstrated by a RR-dependent targeting of translocation-incompatible Tat substrates to the cell poles, and because TatC is required for the formation of aligned TatA tubes, it is proposed that the TatA tubes are initiated at polarly localized TatC.Folded proteins can be transported across membranes by the twin-arginine translocation (Tat) 3 system (1). The mechanism of this transport is unknown but must be quite unusual, because the transported proteins can be even larger in diameter than the membrane they are transported across (2). The minimal Tat translocon is composed of two components, TatA and TatC (3, 4). Proteobacteria and thylakoids require a third component for efficient translocation, TatB, which associates with TatC to form a TatBC complex (1). Because Tat substrates bind tightly only to TatBC complexes, and because a covalent cross-link to TatC still allows translocation, it is believed that TatC is the motor for the translocation process (5). TatA, however, also plays an essential role, most likely by allowing the membrane passage of the substrate, which is moved by TatC across the membrane (6). TatA is also the most abundant Tat component in Escherichia coli (7). In the chloroplast system, the association of TatA with the TatBC complex occurs strictly after substrate binding (6), whereas TatA of Gram-positive bacteria has been detected inside the cytoplasm, where it has a high affinity for Tat substrates that might be targeted by TatA to the membranes (8 -10). TatA of the E. coli Tat system is known to form homooligomeric complexes (11). It has been purified from detergent-solubilized membrane fractions of strains overexpressing the tatABC genes (12). The TatA complexes identified in that study varied in diameter and formed a ladder in blue native polyacrylamide gel electrophoresis (BN-PAGE) analyses. The variable sizes of these TatA complexes suggest the existence of some higher order homooligomeric TatA structure, which might have been disrupted by detergent treatment. We therefore analyzed strains overexpressing tatABC, tatAB, tatAC, or tatA by transmission...

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“…Instead, it has been proposed that DmsD performs a "masking" function by binding to the DmsA signal sequence and rendering it unavailable to direct protein export until after DmsA cofactor attachment has been completed (72). In separate studies, Pop et al present tantalizing evidence that Bacillus subtilis TatA interacts with the Tat-dependent prePhoD substrate prior to its own membrane integration (60), implying that cytoplasmic TatA might chaperone Tat preproteins directly to the site of translocation. Given the involvement of molecular chaperones, a vital question is when do they become associated with preproteins?…”

Section: Vol 186 2004mentioning

confidence: 99%

A Little Help from My Friends: Quality Control of Presecretory Proteins in Bacteria

Fisher

DeLisa

2004

J Bacteriol

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Sequence-specific Binding of prePhoD to Soluble TatAd Indicates Protein-mediated Targeting of the Tat Export in Bacillus subtilis

Abstract: The Tat (twin-arginine protein translocation) system initially discovered in the thylakoid membrane of chloroplasts has been described recently for a variety of eubacterial organisms. Although in Escherichia coli four Tat

Cited by 56 publications

References 69 publications

Genetic and Biochemical Analysis of the Twin-Arginine Translocation Pathway in Halophilic Archaea

Genetic and Biochemical Analysis of the Twin-Arginine Translocation Pathway in Halophilic Archaea

Recombinant Expression of tatABC and tatAC Results in the Formation of Interacting Cytoplasmic TatA Tubes in Escherichia coli

A Little Help from My Friends: Quality Control of Presecretory Proteins in Bacteria

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