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Dimerization and DNA‐dependent aggregation of the Escherichia coli nucleoid protein and chaperone CbpA
Author(s) -
Cosgriff Sarah,
Chintakayala Kiran,
Chim Ya Tsz A.,
Chen Xinyong,
Allen Stephanie,
Lovering Andrew L.,
Grainger David C.
Publication year - 2010
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2010.07292.x
Subject(s) - nucleoid , biology , escherichia coli , chaperone (clinical) , escherichia coli proteins , dna , microbiology and biotechnology , protein aggregation , biochemistry , genetics , gene , medicine , pathology
Summary 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.