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in gram-negative bacteria. Mol Microbiol 1999,31(1):319–329.PubMedCrossRef Authors’ contributions EK conceived the study, performed all experiments and drafted the manuscript. AD helped to finalize the manuscript and to place it in perspective, OS helped to analyse the data and to draft the manuscript. All authors read and approved the final manuscript.”
“Background Ferredoxin (Fdx) is the name given to a variety of small proteins binding inorganic clusters organized around two to four iron atoms and a complementary number of sulfur atoms [1]. Complete genomic sequences have revealed the presence of a very large number of genes encoding such proteins, mainly in bacteria and archaea [2]. Fdxs are most often assigned selleck inhibitor electron transfer roles and some of them occupy central positions in metabolism [3], but the roles of a majority of Fdxs remain unknown [4, 5]. Functional substitution among Fdxs may occur, and other soluble electron shuttles, such as flavodoxins,

may act as Fdx-substitutes. This is the case upon iron starvation for a 2[4Fe-4S] Fdx in glycolytic Clostridia [6] or a [2Fe-2S] Fdx in some photosynthetic organisms [7], for instance. Despite this apparent functional redundancy, most sequenced genomes display a wealth of genes Liothyronine Sodium encoding various Fdxs. For example, the reference PAO1 strain of the opportunistic pathogen Pseudomonas aeruginosa [8] has at least 6 genes encoding Fdxs of different families. A flavodoxin (PA3435) is also present in this strain. It is often unclear in which reactions Fdxs are involved and which biological function relies on a given Fdx. One of P. aeruginosa Fdxs is encoded by the PA0362 locus (fdx1) and it belongs to a separated family of proteins containing two [4Fe-4S] clusters [9]. The sequences of proteins of this family are characterized by a segment of six amino acids between two cysteine ligands of one cluster and a C terminal extension of more than 20 amino acids beyond the last ligand of the other cluster (Figure 1).