Alternative Pathways for Siroheme Synthesis in<i>Klebsiella aerogenes</i>

Kolko, Miriam; Kapetanovich, Lori A.; Lawrence, Jeffrey G.

doi:10.1128/jb.183.1.328-335.2001

Cited by 12 publications

(7 citation statements)

References 28 publications

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“…We did not isolate mutants lacking acetylserine thiolyase activity, which would only be corrected by cysteine; this enzyme may be encoded by redundant genes, since in E. coli and Salmonella both the cysM or cysK genes encode acetylserine thiolyases. Similarly, we did not isolate mutations in the cysG gene in this screen due to the presence of the functionally redundant cysF gene (17). In addition, we did not isolate mutations in the cysE gene, encoding serine transacetylase; this gene may be duplicated, may provide an additional function essential to Klebsiella, thereby preventing the isolation of cysE null mutants, or we may have been unlucky.…”

Section: Resultsmentioning

confidence: 97%

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Methionine-to-Cysteine Recycling in Klebsiella aerogenes

Seiflein

Lawrence

2001

J Bacteriol

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In the enteric bacteria Escherichia coli and Salmonella enterica, sulfate is reduced to sulfide and assimilated into the amino acid cysteine; in turn, cysteine provides the sulfur atom for other sulfur-bearing molecules in the cell, including methionine. These organisms cannot use methionine as a sole source of sulfur. Here we report that this constraint is not shared by many other enteric bacteria, which can use either cysteine or methionine as the sole source of sulfur. The enteric bacterium Klebsiella aerogenes appears to use at least two pathways to allow the reduced sulfur of methionine to be recycled into cysteine. In addition, the ability to recycle methionine on solid media, where cys mutants cannot use methionine as a sulfur source, appears to be different from that in liquid media, where they can. One pathway likely uses a cystathionine intermediate to convert homocysteine to cysteine and is induced under conditions of sulfur starvation, which is likely sensed by low levels of the sulfate reduction intermediate adenosine-5-phosphosulfate. The CysB regulatory proteins appear to control activation of this pathway. A second pathway may use a methanesulfonate intermediate to convert methionine-derived methanethiol to sulfite. While the transsulfurylation pathway may be directed to recovery of methionine, the methanethiol pathway likely represents a general salvage mechanism for recovery of alkane sulfide and alkane sulfonates. Therefore, the relatively distinct biosyntheses of cysteine and methionine in E. coli and Salmonella appear to be more intertwined in Klebsiella.

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Section: Resultsmentioning

confidence: 97%

“…2). Assignment of the cysG linkage group was complicated by the presence of the functionally redundant cysF gene; the characterization of these loci is discussed elsewhere (17). Four linkage groups of met mutations were uncovered.…”

Section: Resultsmentioning

confidence: 99%

Methionine-to-Cysteine Recycling in Klebsiella aerogenes

Seiflein

Lawrence

2001

J Bacteriol

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“…Due to the low solubility of the protein, the sirohydrochlorin ferrochelatase activity of NirR was determined in complementation experiments using the E. coli Δ302a mutant. This strain lacks the E. coli cysG gene, and because it is unable to synthesize sirohaem, it only grows in medium supplemented with cysteine or sulfide, or when the strain expresses other proteins capable of producing sirohaem . Thus, the E. coli Δ302a expressing Methanothermobacter thermautotrophicus sirC and P. denitrificans cobA from plasmid pCIQ was transformed with plasmid pET‐23 expressing S. aureus nirR gene, and the growth in minimal medium with no cysteine was evaluated.…”

Section: Resultsmentioning

confidence: 99%

“…Plasmid pCIQ‐sirCcobA for expression of Methanothermobacter thermautotrophicus sirC and P. denitrificans uroporphyrinogen III methyltransferase cobA genes was introduced into E. coli 302Δa, which is a strain that lacks sirohaem synthase cysG and, thus, is unable to synthesize sirohaem. Therefore, this strain, which does not reduce sulfite to sulfide due to the absence of sirohaem in the sulfite reductase, only grows in the presence of sulfide or cysteine .…”

Section: Methodsmentioning

confidence: 99%

Identification of the sirohaem biosynthesis pathway in Staphylococcus aureus

et al. 2019

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Sirohaem is a modified tetrapyrrole and a key prosthetic group of several enzymes involved in nitrogen and sulfur metabolisms. This work shows that Staphylococcus aureus produces sirohaem through a pathway formed by three independent enzymes. Of the two putative sirohaem synthases encoded in the S. aureus genome and annotated as cysG, one is herein shown to be a uroporphyrinogen III methyltransferase that converts uroporphyrinogen III to precorrin‐2, and was renamed as UroM. The second cysG gene encodes a precorrin‐2 dehydrogenase that converts precorrin‐2 to sirohydrochlorin, and was designated as P2D. The last step was found to be performed by the gene nirR that, in fact, codes for a protein with sirohydrochlorin ferrochelatase activity, labelled as ShfC. Additionally, site‐directed mutagenesis studies of S. aureus ShfC revealed that residues H22 and H87, which are predicted by homology modelling to be located at the active site, control the ferrochelatase activity. Within bacteria, sirohaem synthesis may occur via one, two or three enzymes, and we propose to name the correspondent pathways as Types 1, 2 and 3, respectively. A phylogenetic analysis revealed that Type 1 is the most used pathway in Gammaproteobacteria and Streptomycetales, Type 2 predominates in Fibrobacteres and Vibrionales, and Type 3 predominates in Firmicutes of the Bacillales order. Altogether, we concluded that the current distribution of sirohaem pathways within bacteria, which changes at the genus or species level and within taxa, seems to be the result of evolutionary multiple fusion/fission events.

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“…Transposition-defective derivatives of Tn10-Tn10LK (kanamycin resistant), Tn10dTc (tetracycline resistant), and Tn10dCm (chloramphenicol resistant) were delivered into pTAS1-or pMMK1-bearing strains of K. pneumoniae with bacteriophage delivery vectors NK1205, NK1323, and NK1324 as previously described (13). All insertion mutations were transduced into their maternal parent strain following mutagenesis to ensure 100% linkage of the antibiotic resistance marker to the observed mutant phenotype; transduction was mediated by bacteriophage P1-vir as previously described (13).…”

Section: Methodsmentioning

confidence: 99%

Two Transsulfurylation Pathways in Klebsiella pneumoniae

Seiflein

Lawrence

2006

J Bacteriol

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In most bacteria, inorganic sulfur is assimilated into cysteine, which provides sulfur for methionine biosynthesis via transsulfurylation. Here, cysteine is transferred to the terminal carbon of homoserine via its sulfhydryl group to form cystathionine, which is cleaved to yield homocysteine. In the enteric bacteria Escherichia coli and Salmonella enterica, these reactions are catalyzed by irreversible cystathionine-␥-synthase and cystathionine-␤-lyase enzymes. Alternatively, yeast and some bacteria assimilate sulfur into homocysteine, which serves as a sulfhydryl group donor in the synthesis of cysteine by reverse transsulfurylation with a cystathionine-␤-synthase and cystathionine-␥-lyase. Herein we report that the related enteric bacterium Klebsiella pneumoniae encodes genes for both transsulfurylation pathways; genetic and biochemical analyses show that they are coordinately regulated to prevent futile cycling. Klebsiella uses reverse transsulfurylation to recycle methionine to cysteine during periods of sulfate starvation. This methionine-to-cysteine (mtc) transsulfurylation pathway is activated by cysteine starvation via the CysB protein, by adenosyl-phosphosulfate starvation via the Cbl protein, and by methionine excess via the MetJ protein. While mtc mutants cannot use methionine as a sulfur source on solid medium, they will utilize methionine in liquid medium via a sulfide intermediate, suggesting that an additional nontranssulfurylation methionine-to-cysteine recycling pathway(s) operates under these conditions.Bacterial physiology is a complex network of interwoven biochemical pathways involving numerous shared intermediates, disparately regulated enzymes, and keystone metabolites with important roles as substrates, products, regulatory effectors, or a combination of all three. When genomes gain and lose genes-as they do with startling frequency (20)-the addition of new enzymes and loss of others alter pools of metabolites, overall energy demands, drains on carbon and nitrogen pools, and the balance between transport and de novo biosynthesis. While comparative genomics provides a record of changes in the gene inventory, insight into how the cell responds to such changes is achieved by comparative genetic analyses, where metabolic differences among related organisms are correlated with changes both in their genetic and genomic makeup and in the deployment of their regulatory apparatuses.Here we examine differences in sulfur amino acid metabolism among three well-studied enteric bacteria, Escherichia coli, Salmonella enterica, and Klebsiella pneumoniae. E. coli and Salmonella serve as model systems for the physiology of sulfur assimilation. In these organisms, sulfate is reduced to sulfide and assimilated into acyl-activated serine to form cysteine (14); cysteine then serves as the sulfur group donor, either directly or indirectly, for the synthesis of all other sulfur-bearing molecules in the cell, including methionine. In methionine biosynthesis, cysteine is combined with acyl-activated homoserine to ...

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Alternative Pathways for Siroheme Synthesis inKlebsiella aerogenes

Cited by 12 publications

References 28 publications

Methionine-to-Cysteine Recycling in Klebsiella aerogenes

Methionine-to-Cysteine Recycling in Klebsiella aerogenes

Identification of the sirohaem biosynthesis pathway in Staphylococcus aureus

Two Transsulfurylation Pathways in Klebsiella pneumoniae

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