Expression of the iron-responsive irpA gene from the cyanobacterium Synechococcus sp. strain PCC 7942

Durham, Kathryn A.; Porta, David; McKay, R. Michael L.; Bullerjahn, George S.

doi:10.1007/s00203-002-0503-6

Cited by 17 publications

(15 citation statements)

References 13 publications

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“…This implies that in the IdiB-free mutant a transcript consisting of orf6 and idiC is still present, while the tricistronic orf6-idiC-idiB transcript is absent. As a consequence of the absence of IdiB, IdiA, which has a function in protection of PS II (Michel and Pistorius 2004;Lax et al 2007), and IrpA, whose function so far is still unclear (Durham et al 2003;Reddy et al 1988), are also absent. The IdiB-free mutant has previously been characterized (Yousef et al 2003) and shows many characteristics of an IdiA-free S. elongatus PCC 7942 mutant (Michel et al 1996).…”

Section: Discussionmentioning

confidence: 95%

Characterization of the putative iron sulfur protein IdiC (ORF5) in Synechococcus elongatus PCC 7942

et al. 2007

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The IdiC protein (iron deficiency induced protein C) is encoded by orf5 (now called idiC), which is part of the iron-responsive idiB operon of Synechococcus elongatus PCC 7942. The 20.5 kDa IdiC protein has a putative transmembrane helix and belongs to the thioredoxin (TRX)-like [2Fe-2S] ferredoxin family. IdiC has the highest similarity to the peripheral subunit NuoE of the Escherichia coli NDH-1 complex. IdiC expression increased under iron starvation and also in the late growth phase, representing growth conditions, which favor photosynthetic cyclic and respiratory electron transport over photosynthetic linear electron transport from water to NADP+. Attempts to insertionally inactivate the idiC gene generated merodiploid mutants with a strongly reduced IdiC content (mutant MuD) but no IdiC-free mutant. Thus, IdiC seems to be an essential protein for the viability of S. elongatus under the used experimental conditions. Comparative analyses of S. elongatus wild type (WT) and mutant MuD showed that under iron limitation in WT and MuD the amount of the reaction center proteins PsbA and PsaA/B was highly reduced. MuD had a lower growth rate, chlorophyll content, and photosynthetic O2 evolving activity with bicarbonate as electron acceptor than WT. Immunoblot analyses also showed that in MuD, when grown under iron limitation, the amount of the proteins IdiC and IdiB was greatly reduced as compared to WT. As a consequence of the reduction of the transcription factor IdiB, IdiA and IrpA expression were also decreased. In addition, the IsiA protein concentration was lower in MuD than in WT, although the isiA mRNA was equally high in MuD and WT. Another significant difference was the lower expression of the ferredoxin:NADP+ oxidoreductase in mutant MuD under iron limitation compared to WT. A possible function of the protein IdiC in cyclic electron transport around photosystem I and/or in respiratory electron transport will be discussed.

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Section: Discussionmentioning

confidence: 95%

Characterization of the putative iron sulfur protein IdiC (ORF5) in Synechococcus elongatus PCC 7942

et al. 2007

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“…For example, RL0322, or irpA, resembles an uncharacterized iron-responsive gene from Synechococcus sp. PCC 7942 that is required for Felimited growth (Durham et al 2003), and RL2703 is predicted to encode the fumarate hydratase FumA, a Krebs cycle enzyme containing a [4Fe-4S] cluster. Three other genes with ICE sequences in their regulatory regions were of interest for several reasons, as follows.…”

Section: Identification Of Ice Sequences In the Genome Of R Leguminomentioning

confidence: 99%

The Rhizobium leguminosarum regulator IrrA affects the transcription of a wide range of genes in response to Fe availability

et al. 2006

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We show that an unusual transcriptional regulator, called IrrA, regulates many genes in the symbiotic N2-fixing bacterium Rhizobium leguminosarum in response to iron availability. Several operons in R. leguminosarum are expressed at lower levels in cells grown in Fe-depleted compared to Fe-replete medium. These include hemA1, which encodes the haem biosynthesis enzyme amino-levulinic acid synthase; sufS2BCDS1XA, which specify enzymes for FeS cluster synthesis; rirA, a global, Fe-responsive transcriptional repressor; RL0400, which likely encodes an unusual FeS cluster scaffold; and the possible ferri-siderophore ABC transporter rrp1. Reduced expression in Fe-depleted medium was effected by IrrA, a member of the Fur super-family, which in Bradyrhizobium, the symbiont of soybeans, and in the mammalian pathogen Brucella, is unstable in Fe-replete conditions, due to an interaction with haem. The R. leguminosarum IrrA likely interacts with ICE (iron-control element) motifs, conserved sequences near the promoters of its target genes. The rirA, sufS2BCDS1XA and rrp1 genes are also known to be regulated by RirA, which represses their expression in Fe-replete medium. We present a possible model for iron-responsive gene regulation in Rhizobium, in which the IrrA and RirA regulators, working in parallel, respond to the intracellular availability of haem and, possibly, of FeS clusters respectively. Thus, these regulators may sense the physiological consequences of extraneous Fe concentrations, rather than the concentration of Fe per se, as happens in those bacteria (e.g. Escherichia coli) in which the ferric uptake regulator Fur is the global Fe-responsive gene regulator.

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“…Another conserved member of the candidate iron regulons, the hypothetical gene irpA, was often found to be adjacent to the bfd-bfr genes, suggesting that its product could be also involved in iron storage. In agreement with this, the irpA gene in a cyanobacterium, Synechococcus sp., is induced under Fe deficiency and is involved in Fe-limited growth [56]. Another highly conserved and rather unusual member of the Irr regulon, which may play a role in iron storage, is encoded by the mbfA gene.…”

Section: Functional Content Of Candidate Iron Regulonsmentioning

confidence: 99%

Computational reconstruction of iron- and manganese-responsive transcriptional networks in alpha-proteobacteria

Rodionov¹,

Gelfand²,

Todd³

et al. 2005

PLoS Comp Biol

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We used comparative genomics to investigate the distribution of conserved DNA-binding motifs in the regulatory regions of genes involved in iron and manganese homeostasis in alpha-proteobacteria. Combined with other computational approaches, this allowed us to reconstruct the metal regulatory network in more than three dozen species with available genome sequences. We identified several classes of cis-acting regulatory DNA motifs (Irr-boxes or ICEs, RirA-boxes, Iron-Rhodo-boxes, Fur-alpha-boxes, Mur-box or MRS, MntR-box, and IscR-boxes) in regulatory regions of various genes involved in iron and manganese uptake, Fe-S and heme biosynthesis, iron storage, and usage. Despite the different nature of the iron regulons in selected lineages of alpha-proteobacteria, the overall regulatory network is consistent with, and confirmed by, many experimental observations. This study expands the range of genes involved in iron homeostasis and demonstrates considerable interconnection between iron-responsive regulatory systems. The detailed comparative and phylogenetic analyses of the regulatory systems allowed us to propose a theory about the possible evolution of Fe and Mn regulons in alpha-proteobacteria. The main evolutionary event likely occurred in the common ancestor of the Rhizobiales and Rhodobacterales, where the Fur protein switched to regulating manganese transporters (and hence Fur had become Mur). In these lineages, the role of global iron homeostasis was taken by RirA and Irr, two transcriptional regulators that act by sensing the physiological consequence of the metal availability rather than its concentration per se, and thus provide for more flexible regulation.

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Expression of the iron-responsive irpA gene from the cyanobacterium Synechococcus sp. strain PCC 7942

Cited by 17 publications

References 13 publications

Characterization of the putative iron sulfur protein IdiC (ORF5) in Synechococcus elongatus PCC 7942

Characterization of the putative iron sulfur protein IdiC (ORF5) in Synechococcus elongatus PCC 7942

The Rhizobium leguminosarum regulator IrrA affects the transcription of a wide range of genes in response to Fe availability

Computational reconstruction of iron- and manganese-responsive transcriptional networks in alpha-proteobacteria

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