CspD is a stationary phase-induced, stress response protein in the CspA family of Escherichia coli. Here, we demonstrate that overproduction of CspD is lethal, with the cells displaying a morphology typical of cells with impaired DNA replication. CspD consists mainly of β-strands, and the purified protein exists exclusively as a dimer and binds to single-stranded (ss)DNA and RNA in a dose-dependent manner without apparent sequence specificity. CsdD effectively inhibits both the initiation and the elongation steps of minichromosome replication in vitro. Electron microscopic studies revealed that CspD tightly packs ssDNA, resulting in structures distinctly different from those of SSB-coated DNA. We propose that CspD dimers, with two independent β-sheets interacting with ssDNA, function as a novel inhibitor of DNA replication and play a regulatory role in chromosomal replication in nutrient-depleted cells.
No Supplementary Data
No Article Media
Document Type: Research Article
Department of Biochemistry and Molecular Biology, Georgetown University Medical Center, Washington, DC 20007-2197, USA
Department of Biochemistry, Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA.
March 1, 2001