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.
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