The Moraxella adhesin UspA1 binds to its human CEACAM1 receptor by a deformable trimeric coiled-coil

• Rebecca Conners ^[1] ; Darryl J Hill ^[1] ; Elena Borodina ^[1] ; Christopher Agnew ^[1] ; Sarah J Daniell ^[1] ; Nicholas M Burton ^[1] ; Richard B Sessions ^[1] ; Anthony R Clarke ^[1] ; Lucy E Catto ^[1] ; Donna Lammie ^[2] ; Timothy Wess ^[2] ; R Leo Brady ^[1] ; Mumtaz Virji ^[1]
  1. [1] University of Bristol

     University of Bristol

     Reino Unido

     
  2. [2] Cardiff University

     Cardiff University

     Castle, Reino Unido

     
• Localización: EMBO journal: European Molecular Biology Organization, ISSN 0261-4189, Vol. 27, Nº. 12, 2008, págs. 1779-1789
• Idioma: inglés
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• Resumen

  • Moraxella catarrhalis is a ubiquitous human-specific bacterium commonly associated with upper and lower respiratory tract infections, including otitis media, sinusitis and chronic obstructive pulmonary disease. The bacterium uses an autotransporter protein UspA1 to target an important human cellular receptor carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1). Using X-ray crystallography, we show that the CEACAM1 receptor-binding region of UspA1 unusually consists of an extended, rod-like left-handed trimeric coiled-coil. Mutagenesis and binding studies of UspA1 and the N-domain of CEACAM1 have been used to delineate the interacting surfaces between ligand and receptor and guide assembly of the complex. However, solution scattering, molecular modelling and electron microscopy analyses all indicate that significant bending of the UspA1 coiled-coil stalk also occurs. This explains how UspA1 can engage CEACAM1 at a site far distant from its head group, permitting closer proximity of the respective cell surfaces during infection.