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      Crystallization and preliminary X-ray diffraction analyses of several forms of the CfaB major subunit of enterotoxigenic Escherichia coli CFA/I fimbriae

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          Three fusion proteins were generated in order to resolve the atomic structure of the CFA/I fimbriae of enterotoxigenic E. coli. CfaEB is a fusion of the minor and major CFA/I subunits, while CfaBB and CfaBBB are tandem fusions of two and three repeats, respectively, of the major subunit. Each protein was crystallized and the crystal structures of each of these fusions were determined successively by the molecular-replacement method using the CfaE crystal structure as an initial phasing model.


          Enterotoxigenic Escherichia coli (ETEC), a major global cause of diarrhea, initiates the pathogenic process via fimbriae-mediated attachment to the small intestinal epithelium. A common prototypic ETEC fimbria, colo­nization factor antigen I (CFA/I), consists of a tip-localized minor adhesive subunit CfaE and the stalk-forming major subunit CfaB, both of which are necessary for fimbrial assembly. To elucidate the structure of CFA/I at atomic resolution, three recombinant proteins were generated consisting of fusions of the minor and major subunits (CfaEB) and of two (CfaBB) and three (CfaBBB) repeats of the major subunit. Crystals of CfaEB diffracted X-rays to 2.1 Å resolution and displayed the symmetry of space group P2 1. CfaBB exhibited a crystal diffraction limit of 2.3 Å resolution and had the symmetry of space group P2 12 12. CfaBBB crystallized in the monoclinic space group C2 and diffracted X-­rays to 2.3 Å resolution. These structures were determined using the molecular-replacement method.

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          Author and article information

          Acta Crystallogr Sect F Struct Biol Cryst Commun
          Acta Cryst. F
          Acta Crystallographica Section F: Structural Biology and Crystallization Communications
          International Union of Crystallography
          1 March 2009
          14 February 2009
          14 February 2009
          : 65
          : Pt 3 ( publisher-idID: f090300 )
          : 242-247
          [a ]Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892-4256, USA
          [b ]Enteric Diseases Department, Infectious Diseases Directorate, Naval Medical Research Center, Silver Spring, MD 20910-7500, USA
          [c ]Department of Pediatrics, Uniformed Services University of the Health Sciences, Bethesda, MD 20814-4799, USA
          Author notes
          Correspondence e-mail: dixia@
          en5349 ACSFCL S1744309109001584
          © Li et al. 2009

          This is an open-access article distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.

          Crystallization Communications


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