The Rieske Fe/S Protein of the Cytochromeb   /f Complex in Chloroplasts

Molik, Sabine; Karnauchov, Ivan; Weidlich, Constanze; Herrmann, Reinhold G.; Klösgen, Ralf Bernd

doi:10.1074/jbc.m106690200

Cited by 125 publications

(35 citation statements)

References 54 publications

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“…3). The Rieske protein of the cytochrome b 6 f complex in chloroplasts is targeted in a Tat-dependent manner, with the uncleaved Tat signal peptide doubling as a signal anchor sequence (22). Both the A. faecalis and ULPAs1 arsenite oxidases have been found associated with spheroplasts, suggesting that the Rieske subunit is either attached to the membrane or perhaps strongly associated to the membrane via another protein.…”

Section: Discussionmentioning

confidence: 98%

Molybdenum-Containing Arsenite Oxidase of the Chemolithoautotrophic Arsenite Oxidizer NT-26

2004

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The chemolithoautotroph NT-26 oxidizes arsenite to arsenate by using a periplasmic arsenite oxidase. Purification and preliminary characterization of the enzyme revealed that it (i) contains two heterologous subunits, AroA (98 kDa) and AroB (14 kDa); (ii) has a native molecular mass of 219 kDa, suggesting an ␣ 2 ␤ 2 configuration; and (iii) contains two molybdenum and 9 or 10 iron atoms per ␣ 2 ␤ 2 unit. The genes that encode the enzyme have been cloned and sequenced. Sequence analyses revealed similarities to the arsenite oxidase of Alcaligenes faecalis, the putative arsenite oxidase of the beta-proteobacterium ULPAs1, and putative proteins of Aeropyrum pernix, Sulfolobus tokodaii, and Chloroflexus aurantiacus. Interestingly, the AroA subunit was found to be similar to the molybdenum-containing subunits of enzymes in the dimethyl sulfoxide reductase family, whereas the AroB subunit was found to be similar to the Rieske iron-sulfur proteins of cytochrome bc 1 and b 6 f complexes. The NT-26 arsenite oxidase is probably exported to the periplasm via the Tat secretory pathway, with the AroB leader sequence used for export. Confirmation that NT-26 obtains energy from the oxidation of arsenite was obtained, as an aroA mutant was unable to grow chemolithoautotrophically with arsenite. This mutant could grow heterotrophically in the presence of arsenite; however, the arsenite was not oxidized to arsenate.Arsenic is ubiquitous in the environment and is most commonly found in an insoluble form associated with rocks and minerals (11). In soluble forms, arsenic occurs as trivalent arsenite [As(III)] and pentavalent arsenate [As(V)]. Arsenate, a phosphate analogue, can enter cells via the phosphate transport system and is toxic because it can interfere with normal phosphorylation processes by replacing phosphate. It was recently demonstrated that arsenite enters cells at a neutral pH by aqua-glyceroporins (glycerol transport proteins) in bacteria, yeasts, and mammals (23, 39), and its toxicity lies in its ability to bind sulfhydryl groups of cysteine residues in proteins, thereby inactivating them.Arsenite is considered to be more toxic than arsenate and can be oxidized to arsenate chemically or microbially (12, 16). The arsenite-oxidizing bacteria so far isolated either can gain energy from arsenite oxidation (25,32,33) or have been proposed to do so as part of a detoxification process (14,15,27,30,36). Chemolithoautotrophic arsenite oxidation, for which oxygen is used as the terminal electron acceptor, arsenite is the electron donor, and carbon dioxide is the carbon source, has to date only been reported for organisms isolated from gold mines (32, 33). Aerobic growth with arsenite as the electron donor is exergonic, generating a substantial amount of free energy (32).Arsenite oxidation by the chemolithoautotrophic arsenite oxidizer NT-26, a member of the ␣-Proteobacteria, has been studied in detail (32). Preliminary biochemical studies showed the NT-26 arsenite oxidase (Aro) to be periplasmic and its synthesis to be induc...

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Section: Discussionmentioning

confidence: 98%

Molybdenum-Containing Arsenite Oxidase of the Chemolithoautotrophic Arsenite Oxidizer NT-26

2004

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“…Strikingly, however, the first arginine residue of the typical RR-pair, which was initially believed to be invariant, could be substituted for a lysine residue without blocking the Tat-dependent export of the E. coli SufI protein (12). Moreover, naturally occurring KR-signal peptides, in which the first of the two invariant arginine residues was replaced with a lysine residue, were shown to direct the Tat-dependent translocation of the Salmonella enterica TtrB protein and the Spinacia oleracea Rieske Fe/S protein (13,14). Even an RNR-signal peptide was recently shown to direct a pre-pro-penicillin amidase into the Tat pathway of E. coli (15).…”

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confidence: 99%

Selective Contribution of the Twin-Arginine Translocation Pathway to Protein Secretion in Bacillus subtilis

Jongbloed

Antelmann

Hecker

et al. 2002

Journal of Biological Chemistry

117

148

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The availability of the complete genome sequence of Bacillus subtilis has allowed the prediction of all exported proteins of this Gram-positive eubacterium. Recently, ϳ180 secretory and 114 lipoprotein signal peptides were predicted to direct protein export from the cytoplasm. Whereas most exported proteins appear to use the Sec pathway, 69 of these proteins could potentially use the Tat pathway, as their signal peptides contain RR-or KR-motifs. In the present studies, proteomic techniques were applied to verify how many extracellular B. subtilis proteins follow the Tat pathway. Strikingly, the extracellular accumulation of 13 proteins with potential RR/KR-signal peptides was Tat-independent, showing that their RR/KR-motifs are not recognized by the Tat machinery. In fact, only the phosphodiesterase PhoD was shown to be secreted in a strictly Tat-dependent manner. Sodium azide-inhibition of SecA strongly affected the extracellular appearance of de novo synthesized proteins, including the lipase LipA and two other proteins with predicted RR/KR-signal peptides. The SecAdependent export of pre-LipA is particularly remarkable, because its RR-signal peptide conforms well to stringent criteria for the prediction of Tat-dependent export in Escherichia coli. Taken together, our observations show that the Tat pathway makes a highly selective contribution to the extracellular proteome of B. subtilis.

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“…Only in the case of the Rieske protein has a requirement for stromal chaperones been described. The chaperones are presumably involved in the assembly of the iron-sulfur cluster (25). In contrast, in bacterial Tat systems, several chaperones were found to bind the precursor proteins prior to translocation (26 -29).…”

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confidence: 99%

A Stromal Pool of TatA Promotes Tat-dependent Protein Transport across the Thylakoid Membrane

Frielingsdorf¹,

Jakob

Klösgen

2008

Journal of Biological Chemistry

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In chloroplasts and bacteria, the Tat (twin-arginine translocation) system is engaged in transporting folded passenger proteins across the thylakoid and cytoplasmic membranes, respectively. To date, three membrane proteins (TatA, TatB, and TatC) have been identified to be essential for Tat-dependent protein translocation in the plant system, whereas soluble factors seem not to be required. In contrast, in the bacterial system, several cytosolic chaperones were described to be involved in Tat transport processes. Therefore, we have examined whether stromal or peripherally associated membrane proteins also play a role in Tat transport across the thylakoid membrane. Analyzing both authentic precursors as well as the chimeric 16/23 protein, which allows us to study each step of the translocation process individually, we demonstrate that a soluble form of TatA is present in the chloroplast stroma, which significantly improves the efficiency of Tat-dependent protein transport. Furthermore, this soluble TatA is able to reconstitute the Tat transport properties of thylakoid membranes that are transportincompetent due to extraction with solutions of chaotropic salts.

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The Rieske Fe/S Protein of the Cytochromeb /f Complex in Chloroplasts

Cited by 125 publications

References 54 publications

Molybdenum-Containing Arsenite Oxidase of the Chemolithoautotrophic Arsenite Oxidizer NT-26

Molybdenum-Containing Arsenite Oxidase of the Chemolithoautotrophic Arsenite Oxidizer NT-26

Selective Contribution of the Twin-Arginine Translocation Pathway to Protein Secretion in Bacillus subtilis

A Stromal Pool of TatA Promotes Tat-dependent Protein Transport across the Thylakoid Membrane

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