Dimerization and DNA-dependent aggregation of the Escherichia coli nucleoid protein and chaperone CbpA.
The Escherichia coli curved DNA-binding protein A (CbpA) is a nucleoid-associated DNA-binding factor and chaperone that is expressed at high levels as cells enter stationary phase. Using a combination of genetics, biochemistry, structural modelling and single-molecule atomic force microscopy we have examined dimerization of, and DNA binding by, CbpA. Our data show that CbpA dimerization is driven by a hydrophobic surface comprising amino acid side chains W287 and L290 located on the same side of an α helix close to the C-terminus of CbpA. Derivatives of CbpA that are unable to dimerize are also unable to bind DNA. Free in solution, CbpA can exist as either a monomer or dimer. However, when bound to DNA, CbpA forms large aggregates that can protect DNA from degradation by nucleases. These CbpA-DNA aggregates are similar in morphology to protein-DNA complexes formed by the DNA-binding protein from starved cells (Dps), the only other stationary phase-specific nucleoid protein. Conversely, protein-DNA complexes formed by Fis, the major growth phase nucleoid protein, have a markedly different appearance.
Cosgriff
Sarah
S
Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK.
Chintakayala
Kiran
K
Chim
Ya Tsz A
YT
Chen
Xinyong
X
Allen
Stephanie
S
Lovering
Andrew L
AL
Grainger
David C
DC
D004269:DNA, Bacterial / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D011485:Protein Binding; D055503:Protein Multimerization
C085674:CbpA protein, E coli; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins