Spiral structure of Escherichia coli HUαβ provides foundation for DNA supercoiling
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Contributed by Sankar Adhya, January 4, 2007 (received for review October 5, 2006)
Abstract
We determined the crystal structure of the Escherichia coli nucleoid-associated HUαβ protein by x-ray diffraction and observed that the heterodimers form multimers with octameric units in three potential arrangements, which may serve specialized roles in different DNA transaction reactions. It is of special importance that one of the structures forms spiral filaments with left-handed rotations. A negatively superhelical DNA can be modeled to wrap around this left-handed HUαβ multimer. Whereas the wild-type HU generated negative DNA supercoiling in vitro, an engineered heterodimer with an altered amino acid residue critical for the formation of the left-handed spiral protein in the crystal was defective in the process, thus providing the structural explanation for the classical property of HU to restrain negative supercoils in DNA.
Footnotes
- *To whom correspondence should be addressed at: National Cancer Institute, 37 Convent Drive, Room 5138, Bethesda, MD 20892-4264. E-mail: sadhya{at}helix.nih.gov
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Author contributions: F.G. and S.A. designed research; F.G. performed research; F.G. and S.A. analyzed data; and F.G. and S.A. wrote the paper.
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The authors declare no conflict of interest.
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Data deposition: The structure factors have been deposited in the Protein Data Bank, www.pdb.org (PDB ID code 2O97).
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This article contains supporting information online at www.pnas.org/cgi/content/full/0611686104/DC1.
- © 2007 by The National Academy of Sciences of the USA
