DNA condensation and self-aggregation of Escherichia coli Dps are coupled phenomena related to the properties of the N-terminus (original) (raw)

2004, Nucleic Acids Research

Escherichia coli Dps (DNA-binding proteins from starved cells) is the prototype of a DNA-protecting protein family expressed by bacteria under nutritional and oxidative stress. The role of the lysine-rich and highly mobile Dps N-terminus in DNA protection has been investigated by comparing the self-aggregation and DNA-condensation capacity of wild-type Dps and two N-terminal deletion mutants, DpsD8 and DpsD18, lacking two or all three lysine residues, respectively. Gel mobility and atomic force microscopy imaging showed that at pH 6.3, both wild type and DpsD8 self-aggregate, leading to formation of oligomers of variable size, and condense DNA with formation of large Dps-DNA complexes. Conversely, DpsD18 does not self-aggregate and binds DNA without causing condensation. At pH 8.2, DpsD8 and DpsD18 neither self-aggregate nor cause DNA condensation, a behavior also displayed by wild-type Dps at pH 8.7. Thus, Dps self-aggregation and Dps-driven DNA condensation are parallel phenomena that reflect the properties of the N-terminus. DNA protection against the toxic action of Fe(II) and H 2 O 2 is not affected by the N-terminal deletions either in vitro or in vivo, in accordance with the different structural basis of this property.

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