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Biometals : an international journal on the role of metal ions in biology, biochemistry, and medicine (1)
PLoS ONE (1)
Wu, Genfu (2)
Bitoun, Jacob P. (1)
Ding, Huangen (1)
Fu, Huihui (1)
Gao, Haichun (1)
Jiang, Yaoming (1)
Jin, Miao (1)
Saraiva, Ligia M (1)
Sun, Linlin (1)
Yin, Jianhua (1)
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Unique Organizational and Functional Features of the Cytochrome c Maturation System in Shewanella oneidensis
Saraiva, Ligia M
Shewanella are renowned for their ability to respire on a wide range of electron acceptors, which has been partially accredited to the presence of a large number of the c-type cytochromes. In the model species S. oneidensis MR-1, at least 41 genes encode c-type cytochromes that are predicted to be intact, thereby likely functional. Previously, in-frame deletion mutants for 36 of these genes were obtained and characterized. In this study, first we completed the construction of an entire set of c-type cytochrome mutants utilizing a newly developed att-based mutagenesis approach, which is more effective and efficient than the approach used previously by circumventing the conventional cloning. Second, we investigated the cytochrome c maturation (Ccm) system in S. oneidensis. There are two loci predicted to encode components of the Ccm system, SO0259-SO0269 and SO0476-SO0478. The former is proven essential for cytochrome c maturation whereas the latter is dispensable. Unlike the single operon organization observed in other γ-proteobacteria, genes at the SO0259-SO0269 locus are uniquely organized into four operons, ccmABCDE, scyA, SO0265, and ccmFGH-SO0269. Functional analysis revealed that the SO0265 gene rather than the scyA and SO0269 genes are relevant to cytochrome c maturation.
Escherichia coli FtnA Acts as an Iron Buffer for Re-assembly of Iron-Sulfur Clusters in Response to Hydrogen Peroxide Stress
Bitoun, Jacob P.
Biometals : an international journal on the role of metal ions in biology, biochemistry, and medicine
Iron-sulfur clusters are one of the most ubiquitous redox centers in biology. Ironically, iron-sulfur clusters are highly sensitive to reactive oxygen species. Disruption of iron-sulfur clusters will not only change the activity of proteins that host iron-sulfur clusters, the iron released from the disrupted iron-sulfur clusters will further promote the production of deleterious hydroxyl free radicals via the Fenton reaction. Here, we report that ferritin A (FtnA), a major iron-storage protein in Escherichia coli, is able to scavenge the iron released from the disrupted iron-sulfur clusters and alleviates the production of hydroxyl free radicals. Furthermore, we find that the iron stored in ferritin A can be retrieved by an iron chaperon IscA for the re-assembly of the iron-sulfur cluster in a proposed scaffold IscU in the presence of the thioredoxin reductase system which emulates normal intracellular redox potential. The results suggest that E. coli ferritin A may act as an iron buffer to sequester the iron released from the disrupted iron-sulfur clusters under oxidative stress conditions and to facilitate the re-assembly of the disrupted iron-sulfur clusters under normal physiological conditions.
Ferritin A; hydroxyl free radicals; iron-sulfur clusters; IscA; IscU
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