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  • 1
    Electronic Resource
    Electronic Resource
    The nrfI gene is essential for the attachment of the active site haem group of Wolinella succinogenes cytochrome c nitrite reductase (2002)
    Oxford, UK : Blackwell Science Ltd.
    Molecular microbiology 43 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The cytochrome c nitrite reductase complex (NrfHA) is the terminal enzyme in the electron transport chain catalysing nitrite respiration of Wolinella succinogenes. The catalytic subunit NrfA is a pentahaem cytochrome c containing an active site haem group which is covalently bound via the cysteine residues of a unique CWTCK motif. The lysine residue serves as the axial ligand of the haem iron. The other four haem groups of NrfA are bound by conventional haem-binding motifs (CXXCH). The nrfHAIJ locus was restored on the genome of the W. succinogenesΔnrfAIJ deletion mutant by integration of a plasmid, thus enabling the expression of modified alleles of nrfA and nrfI. A mutant (K134H) was constructed which contained a nrfA gene encoding a CWTCH motif instead of CWTCK. NrfA of strain K134H was found to be synthesized with five bound haem groups, as judged by matrix-assisted laser-desorption/ionization (MALDI) mass spectrometry. Its nitrite reduction activity with reduced benzyl viologen was 40% of the wild-type activity. Ammonia was formed as the only product of nitrite reduction. The mutant did not grow by nitrite respiration and its electron transport activity from formate to nitrite was 5% of that of the wild-type strain. The predicted nrfI gene product is similar to proteins involved in system II cytochrome c biogenesis. A mutant of W. succinogenes (stopI) was constructed that contained a nrfHAIJ gene cluster with the nrfI codons 47 and 48 altered to stop codons. The NrfA protein of this mutant did not catalyse nitrite reduction and lacked the active site haem group, whereas the other four haem groups were present. Mutant (K134H/stopI) which contained the K134H modification in NrfA in addition to the inactivated nrfI gene had essentially the same properties as strain K134H. NrfA from strain K134H/stopI contained five haem groups. It is concluded that NrfI is involved in haem attachment to the CWTCK motif in NrfA but not to any of the CXXCH motifs. The nrfI gene is obviously dispensable for maturation of a modified NrfA protein containing a CWTCH motif instead of CWTCK. Therefore, NrfI might function as a specific haem lyase that recognizes the active site lysine residue of NrfA. A similar role has been proposed for NrfE, F and G of Escherichia coli, although these proteins share no overall sequence similarity to NrfI and belong to system I cytochrome c biogenesis, which differs fundamentally from system II.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.02784.x
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  • 2
    Electronic Resource
    Electronic Resource
    The hydE gene is essential for the formation of Wolinella succinogenes NiFe-hydrogenase (2003)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 227 (2003), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Wolinella succinogenes grows by anaerobic respiration using hydrogen gas as electron donor. The hydE gene is located on the genome downstream of the structural genes encoding the membrane-bound NiFe-hydrogenase complex (HydABC) and a putative protease (HydD) possibly involved in hydrogenase maturation. Homologs of hydE are found in the vicinity of NiFe-hydrogenase-encoding genes on the genomes of several other proteobacteria. A hydE deletion mutant of W. succinogenes does not catalyze hydrogen oxidation with various electron acceptors. The hydrogenase iron–sulfur subunit HydA is absent in mutant cells whereas the apparently processed NiFe subunit (HydB) is located exclusively in the soluble cell fraction. It is suggested that HydE is involved in the maturation and/or stability of HydA or the HydAB complex in some, but not all bacteria containing NiFe-hydrogenases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0378-1097(03)00681-5
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  • 3
    Electronic Resource
    Electronic Resource
    Enzymology and bioenergetics of respiratory nitrite ammonification (2002)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology reviews 26 (2002), S. 0 
    Details
    ISSN: 1574-6976
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Nitrite is widely used by bacteria as an electron acceptor under anaerobic conditions. In respiratory nitrite ammonification an electrochemical proton potential across the membrane is generated by electron transport from a non-fermentable substrate like formate or H2 to nitrite. The corresponding electron transport chain minimally comprises formate dehydrogenase or hydrogenase, a respiratory quinone and cytochrome c nitrite reductase. The catalytic subunit of the latter enzyme (NrfA) catalyzes nitrite reduction to ammonia without liberating intermediate products. This review focuses on recent progress that has been made in understanding the enzymology and bioenergetics of respiratory nitrite ammonification. High-resolution structures of NrfA proteins from different bacteria have been determined, and many nrf operons sequenced, leading to the prediction of electron transfer pathways from the quinone pool to NrfA. Furthermore, the coupled electron transport chain from formate to nitrite of Wolinella succinogenes has been reconstituted by incorporating the purified enzymes into liposomes. The NrfH protein of W. succinogenes, a tetraheme c-type cytochrome of the NapC/NirT family, forms a stable complex with NrfA in the membrane and serves in passing electrons from menaquinol to NrfA. Proteins similar to NrfH are predicted by open reading frames of several bacterial nrf gene clusters. In γ-proteobacteria, however, NrfH is thought to be replaced by the nrfBCD gene products. The active site heme c group of NrfA proteins from different bacteria is covalently bound via the cysteine residues of a unique CXXCK motif. The lysine residue of this motif serves as an axial ligand to the heme iron thus replacing the conventional histidine residue. The attachment of the lysine-ligated heme group requires specialized proteins in W. succinogenes and Escherichia coli that are encoded by accessory nrf genes. The proteins predicted by these genes are unrelated in the two bacteria but similar to proteins of the respective conventional cytochrome c biogenesis systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6976.2002.tb00616.x
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  • 4
    Electronic Resource
    Electronic Resource
    Identification of histidine residues in Wolinella succinogenes hydrogenase that are essential for menaquinone reduction by H2 (1998)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 30 (1998), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The cytochrome b subunit (HydC) of Wolinella succinogenes hydrogenase binds two haem B groups. This is concluded from the haem B content of the isolated hydrogenase and is confirmed by the response of its cytochrome b to redox titration. In addition, three of the four haem B ligands were identified by characterizing mutants with the corresponding histidine residues replaced by alanine or methionine. Substitution in HydC of His-25, His-67 or His-186, which are, in addition to His-200, predicted to be haem B ligands, caused the loss of quinone reactivity of the hydrogenase, while the activity of benzylviologen reduction was retained. The corresponding mutants did not grow with H2 as electron donor and either fumarate or polysulphide as terminal electron acceptor. The mutants grown with formate and fumarate did not catalyse electron transport from H2 to fumarate or to polysulphide, or quinone reduction by H2, in contrast to the wild-type strain. Cytochrome b was not reduced by H2 in the Triton X-100 extract of the mutant membranes, which contained wild-type amounts of the mutated HydC protein. Substitution in HydC of His-122, His-158 or His-187, which are predicted not to be haem B ligands, yielded mutants with wild-type properties. Substitution in HydA of His-188 or of His-305 resulted in mutants with the same properties as those lacking one of the haem B ligands of HydC. His-305 is located in the membrane-integrated C-terminal helix of HydA. His-188 of HydA is predicted to be a ligand of the distal iron–sulphur centre that may serve as the direct electron donor to the haem B groups of HydC. The results suggest that each of the three predicted haem B ligands of HydC tested (out of four) is required for electron transport from H2 to either fumarate or polysulphide, and for quinone reactivity. This also holds true for the two conserved histidine residues of HydA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.01100.x
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  • 5
    Electronic Resource
    Electronic Resource
    Electron transport to periplasmic nitrate reductase (NapA) of Wolinella succinogenes is independent of a NapC protein (2003)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 49 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The rumen bacterium Wolinella succinogenes grows by respiratory nitrate ammonification with formate as electron donor. Whereas the enzymology and coupling mechanism of nitrite respiration is well known, nitrate reduction to nitrite has not yet been examined. We report here that intact cells and cell fractions catalyse nitrate and chlorate reduction by reduced viologen dyes with high specific activities. A gene cluster encoding components of a putative periplasmic nitrate reductase system (napA, G, H, B, F, L, D) was sequenced. The napA gene was inactivated by inserting a kanamycin resistance gene cassette. The resulting mutant did not grow by nitrate respiration and did not reduce nitrate during growth by fumarate respiration, in contrast to the wild type. An antigen was detected in wild-type cells using an antiserum raised against the periplasmic nitrate reductase (NapA) from Paracoccus pantotrophus. This antigen was absent in the W. succinogenes napA mutant. It is concluded that the periplasmic nitrate reductase NapA is the only respiratory nitrate reductase in W. succinogenes, although a second nitrate-reducing enzyme is apparently induced in the napA mutant. The nap cluster of W. succinogenes lacks a napC gene whose product is thought to function in quinol oxidation and electron transfer to NapA in other bacteria. The W. succinogenes genome encodes two members of the NapC/NirT family, NrfH and FccC. Characterization of corresponding deletion mutants indicates that neither of these two proteins is required for nitrate respiration. A mutant lacking the genes encoding respiratory nitrite reductase (nrfHA) had wild-type properties with respect to nitrate respiration. A model of the electron transport chain of nitrate respiration is proposed in which one or more of the napF, G, H and L gene products mediate electron transport from menaquinol to the periplasmic NapAB complex. Inspection of the W. succinogenes genome sequence suggests that ammonia formation from nitrate is catalysed exclusively by periplasmic respiratory enzymes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03544.x
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  • 6
    Electronic Resource
    Electronic Resource
    A NapC/NirT-type cytochrome c (NrfH) is the mediator between the quinone pool and the cytochrome c nitrite reductase of Wolinella succinogenes (2000)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 35 (2000), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Wolinella succinogenes can grow by anaerobic respiration with nitrate or nitrite using formate as electron donor. Two forms of nitrite reductase were isolated from the membrane fraction of W. succinogenes. One form consisted of a 58 kDa polypeptide (NrfA) that was identical to the periplasmic nitrite reductase. The other form consisted of NrfA and a 22 kDa polypeptide (NrfH). Both forms catalysed nitrite reduction by reduced benzyl viologen, but only the dimeric form catalysed nitrite reduction by dimethylnaphthoquinol. Liposomes containing heterodimeric nitrite reductase, formate dehydrogenase and menaquinone catalysed the electron transport from formate to nitrite; this was coupled to the generation of an electrochemical proton potential (positive outside) across the liposomal membrane. It is concluded that the electron transfer from menaquinol to the catalytic subunit (NrfA) of W. succinogenes nitrite reductase is mediated by NrfH. The structural genes nrfA and nrfH were identified in an apparent operon (nrfHAIJ) with two additional genes. The gene nrfA encodes the precursor of NrfA carrying an N-terminal signal peptide (22 residues). NrfA (485 residues) is predicted to be a hydrophilic protein that is similar to the NrfA proteins of Sulfurospirillum deleyianum and of Escherichia coli. NrfH (177 residues) is predicted to be a membrane-bound tetrahaem cytochrome c belonging to the NapC/NirT family. The products of nrfI and nrfJ resemble proteins involved in cytochrome c biogenesis. The C-terminal third of NrfI (902 amino acid residues) is similar to CcsA proteins from Gram-positive bacteria, cyanobacteria and chloroplasts. The residual N-terminal part of NrfI resembles Ccs1 proteins. The deduced NrfJ protein resembles the thioredoxin-like proteins (ResA) of Helicobacter pylori and of Bacillus subtilis, but lacks the common motif CxxC of ResA. The properties of three deletion mutants of W. succinogenes (ΔnrfJ,ΔnrfIJ and ΔnrfAIJ) were studied. Mutants ΔnrfAIJ and ΔnrfIJ did not grow with nitrite as terminal electron acceptor or with nitrate in the absence of NH4+ and lacked nitrite reductase activity, whereas mutant ΔnrfJ showed wild-type properties. The NrfA protein formed by mutant ΔnrfIJ seemed to lack part of the haem C, suggesting that NrfI is involved in NrfA maturation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2000.01742.x
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  • 7
    Electronic Resource
    Electronic Resource
    A periplasmic flavoprotein in Wolinella succinogenes that resembles the fumarate reductase of Shewanella putrefaciens (1998)
    Springer
    Archives of microbiology 169 (1998), S. 424-433 
    Details
    ISSN: 1432-072X
    Keywords: Key words Fumarate reduction ; Sulfide oxidation ; Wolinella succinogenes ; Shewanella putrefaciens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During growth with fumarate as the terminal electron transport acceptor and either formate or sulfide as the electron donor, Wolinella succinogenes induced a peri-plasmic protein (54 kDa) that reacted with an antiserum raised against the periplasmic fumarate reductase (Fcc) of Shewanella putrefaciens. However, the periplasmic cell fraction of W. succinogenes did not catalyze fumarate reduction with viologen radicals. W. succinogenes grown with polysulfide instead of fumarate contained much less (〈 10%) of the 54-kDa antigen, and the antigen was not detectable in nitrate-grown bacteria. The antigen was most likely encoded by the fccA gene of W. succinogenes. The antigen was absent from a ΔfccABC mutant, and its size is close to that of the protein predicted by fccA. The fccA gene probably encodes a pre-protein carrying an N-terminal signal peptide. The sequence of the mature FccA (481 residues, 52.4 kDa) is similar (31% identity) to that of the C-terminal part (450 residues) of S. putrefaciens fumarate reductase. As indicated by Northern blot analysis, fccA is cotranscribed with fccB and fccC. The proteins predicted from the fccB and fccC gene sequences represent tetraheme cytochromes c. FccB is similar to the N-terminal part (150 residues) of S. putrefaciens fumarate reductase, while FccC resembles the tetraheme cytochromes c of the NirT/NapC family. The ΔfccABC mutant of W. succinogenes grew with fumarate and formate or sulfide, suggesting that the deleted proteins were not required for fumarate respiration with either electron donor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050593
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  • 8
    Electronic Resource
    Electronic Resource
    The role of the twin-arginine motif in the signal peptide encoded by the hydA gene of the hydrogenase from Wolinella succinogenes (1999)
    Springer
    Archives of microbiology 172 (1999), S. 227-232 
    Details
    ISSN: 1432-072X
    Keywords: Key words Ni-hydrogenase ; Cytochrome b ; Wolinella succinogenes ; Signal peptide ; Twin-arginine transfer ; Tat system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The hydABC operon of Wolinella succinogenes encodes the three subunits of the membrane-integrated Ni-hydrogenase. The catalytic subunit, HydB, is on the periplasmic side of the membrane. Residues R41 and R42 of the twin-arginine motif within the signal peptide of the precursor of the iron-sulfur subunit, HydA, were replaced by two glutamine residues. The corresponding mutant did not grow with H2 as the electron donor of anaerobic respiration. Mature HydB and the precursor protein of HydA were located exclusively in the cytoplasmic cell fraction of the mutant, which catalyzed the reduction of benzyl viologen by H2, suggesting that HydB contained Ni. The HydC protein was located in the membrane fraction of the mutant in wild-type amounts. HydC was purified and was shown to contain heme. The results suggest that HydA and HydB are translocated across the membrane by the Tat (twin-arginine translocation) system. The translocation of HydA and HydB as well as the maturation of the precursor protein of HydA appear to depend on the presence of the twin-arginine motif. In contrast, maturation of HydB, the insertion of HydC into the membrane, and heme attachment to HydC are apparently independent of the twin-arginine motif and do not require translocation of the two other hydrogenase subunits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050764
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  • 9
    Electronic Resource
    Electronic Resource
    Identification and characterization of IS1302, a novel insertion element from Wolinella succinogenes belonging to the IS3 family (1998)
    Springer
    Archives of microbiology 170 (1998), S. 43-49 
    Details
    ISSN: 1432-072X
    Keywords: Key words Bacterial insertion sequence ; Wolinella ; succinogenes ; Transposase ; IS1302 ; IS3 family
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A new insertion sequence (IS) designated IS1302 was identified in Wolinella succinogenes. IS1302 is 1,306 bp in size with 36-bp imperfect terminal inverted repeats. It contains only one open reading frame (tnpA), which encodes a putative transposase whose sequence is similar to that of transposases of various IS elements of the IS3 family. IS1302 was identified in the genome of a W. succinogenes fumarate reductase deletion mutant in which the frd operon had been replaced by the kan gene. The insertion of IS1302 occurred when the mutant was propagated in the presence of a high concentration of kanamycin. Two different target sites of IS1302 were found immediately upstream of the kan gene, where the insertion of IS1302 resulted in a duplication of 3 bp of the target DNA. Upon insertion of IS1302, new possible promoter structures of the kan gene were created, which might lead to a stimulated transcription of the kan gene and result in a selective advantage of cells containing IS1302 at one of the two target sites. Southern blot analysis suggested the presence of at least 13 copies of IS1302 in the genome of W. succinogenes. This is the first IS element discovered in W. succinogenes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050613
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  • 10
    Electronic Resource
    Electronic Resource
    Two membrane anchors of Wolinella succinogenes hydrogenase and their function in fumarate and polysulfide respiration (1998)
    Springer
    Archives of microbiology 170 (1998), S. 50-58 
    Details
    ISSN: 1432-072X
    Keywords: Key words Membrane-integrated Ni-hydrogenase ; Cytochrome b ; Wolinella succinogenes ; Fumarate ; respiration ; Polysulfide respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Wolinella succinogenes can grow by anaerobic respiration with fumarate or polysulfide as the terminal electron acceptor, and H2 or formate as the electron donor. A ΔhydABC mutant lacking the hydrogenase structural genes did not grow with H2 and either fumarate or polysulfide. In contrast to the wild-type strain, the mutant grown with fumarate and with formate instead of H2 did not catalyze the reduction of fumarate, polysulfide, dimethylnaphthoquinone, or benzyl viologen by H2. Growth and enzymic activities were restored upon integration of a plasmid carrying hydABC into the genome of the ΔhydABC mutant. The ΔhydABC mutant was complemented with hydABC operons modified by artificial stop codons in hydA (StopA) or at the 5′-end of hydC (StopC). The StopC mutant lacked HydC, and the hydrophobic C-terminus of HydA was missing in the hydrogenase of the StopA mutant. The two mutants catalyzed benzyl viologen reduction by H2. The enzyme activity was located in the membrane of the mutants. A mutant with both modifications (StopAC) contained the activity in the periplasm. The three mutants did not grow with H2 and either fumarate or polysulfide, and did not catalyze dimethylnaphthoquinone reduction by H2. We conclude that the same hydrogenase serves in the anaerobic respiration with fumarate and with polysulfide. HydC and the C-terminus of HydA appear to be required for both routes of electron transport and for dimethylnaphthoquinone reduction by H2. The hydrogenase is anchored in the membrane by HydC and by the C-terminus of HydA. The catalytic subunit HydB is oriented towards the periplasmic side of the membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050614
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