Fur regulates the expression of iron-stress genes in the cyanobacterium Synechococcus sp. strain PCC 7942.
A homologue of the 'ferric uptake regulation' gene (fur) was isolated from the cyanobacterium Synechococcus sp. strain PCC 7942 by an Escherichia coli-based 'in vivo repression assay'. The assay uses a reporter-gene construct containing the promoter region of the iron-regulated cyanobacterial gene isiA, fused to the coding region for chloramphenicol acetyltransferase. The isolated gene codes for a protein that has 41% sequence similarity (36% identity) to Fur from E. coli and contains the putative iron-binding motif found in the Fur proteins of purple bacteria. No significant similarity was found to the DxtR repressor that regulates the expression of toxin and siderophore production in Gram-positive bacteria. Insertional mutagenesis of the cloned cyanobacterial fur gene led to the creation of heteroallelic mutants that showed iron-deficiency symptoms in iron-replete medium, including the constitutive production of flavodoxin and of hydroxamate siderophores. Failure to eliminate wild-type copies of the fur gene from the polyploid genome of Synechococcus 7942 implies that in this cyanobacterium Fur may have essential functions in addition to the regulation of genes involved in iron scavenging or photosynthetic electron transport.
Ghassemian
Majid
M
Department of Botany, University of Toronto, 25 Willcocks St, Toronto, Ontario, M5S 3B2Canada.
Straus
Neil A
NA
Department of Botany, University of Toronto, 25 Willcocks St, Toronto, Ontario, M5S 3B2Canada.
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D001682:Biological Availability; D000458:Cyanobacteria / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D005288:Ferredoxins / Q000096:biosynthesis / Q000235:genetics; D005418:Flavodoxin / Q000096:biosynthesis / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D007501:Iron / Q000378:metabolism*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D017262:Siderophores / Q000096:biosynthesis / Q000235:genetics; D013045:Species Specificity
D001426:Bacterial Proteins; D005288:Ferredoxins; D005418:Flavodoxin; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D017262:Siderophores; C068477:ferric uptake regulating proteins, bacterial; D007501:Iron