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Summary: The DNA-binding protein of starved cells (Dps) has two distinct cellular functions in Escherichia coli. The spherical Dps dodecamer can store iron and, predominantly in the stationary growth phase, high amounts of Dps protein protect the genome by binding non-specifically to DNA. In this study we investigated the role of Dps in copper homeostasis in growing cells of E. coli. Under reductive aerobic growth conditions that favor a redox shift from Cu(II) to Cu(I) or under anaerobiosis, cells deleted in dps were sensitive to low copper ion concentrations. Deletion of the DNA-binding N-terminus of Dps did not abrogate protection against copper toxicity indicating protection against copper stress is not directly related to DNA binding of Dps. The Dps protein is not a copper-storage protein in vitro or in vivo. In contrast, cells lacking Dps exhibited increased cellular copper concentrations compared to their wild-type parent. Furthermore, overproduction of Dps during growth phase resulted in decreased intracellular copper content under copper stress. [Copyright &y& Elsevier]

Background: The Escherichia coli heterodimeric HU protein is a small DNA-bending protein associated with the bacterial nucleoid. It can introduce negative supercoils into closed circular DNA in the presence of topoisomerase I. Cells lacking HU grow very poorly and display many phenotypes. Methodology/Principal Findings: We analyzed the transcription profile of every Escherichia coli gene in the absence of one or both HU subunits. This genome-wide in silico transcriptomic approach, performed in parallel with in vivo genetic experimentation, defined the HU regulon. This large regulon, which comprises 8% of the genome, is composed of four biologically relevant gene classes whose regulation responds to anaerobiosis, acid stress, high osmolarity, and SOS induction. Conclusions/Significance: The regulation a large number of genes encoding enzymes involved in energy metabolism and catabolism pathways by HU explains the highly pleiotropic phenotype of HU-deficient cells. The uniform chromosomal distribution of the many operons regulated by HU strongly suggests that the transcriptional and nucleoid architectural functions of HU constitute two aspects of a unique protein-DNA interaction mechanism. [ABSTRACT FROM AUTHOR]

Using the leucine zipper domain of a small anaerobically induced bZIP transcription factor in a yeast two hybrid screen, anaerobically induced genes were identified. One peptide corresponds to an anaerobically induced IDS4-like protein that maybe involved in G-protein signaling. Surprisingly, another interacting peptide corresponds to a novel anaerobically induced 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase, designated ACO5. ACO5 harbours a leucine zipper and transcription is mainly induced in fruits and to a lesser extend in leaves. The role of ACO5 in the low oxygen response of tomato is discussed. [ABSTRACT FROM AUTHOR]