Structure and allosteric regulation of the alpha X beta 2 integrin I domain

  • Vorup-Jensen T
  • Ostermeier C
  • Shimaoka M
 et al. 
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The integrin alpha X beta 2 (CD11c/CD18, p150,95) binds ligands through the I domain of the alpha X subunit. Ligands include the complement factor fragment iC3b, a key component in the innate immune defense, which, together with the expression of alpha X beta 2 on dendritic cells and on other leukocytes, suggests a role in the immune response. We now report the structure of the alpha X I domain resolved at 1.65 A by x-ray crystallography. To analyze structural requirements for ligand binding we made a mutation in the alpha X I domain C-terminal helix, which increased the affinity for iC3b approximately 200-fold to 2.4 microM compared with the wild-type domain affinity of approximately 400 microM. Gel permeation chromatography supported a conformational change between the wild-type and mutated domains. Conservation of allosteric regulation in the alpha X I domain points to the functional importance of this phenomenon.

Author-supplied keywords

  • Allosteric Regulation
  • Amino Acid Sequence
  • Base Sequence
  • Crystallography, X-Ray
  • DNA Primers
  • Integrin alphaXbeta2/*chemistry/genetics/*metaboli
  • Molecular Sequence Data
  • Protein Denaturation
  • Recombinant Proteins/chemistry/genetics/metabolism
  • Sequence Homology, Amino Acid
  • Surface Plasmon Resonance

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  • T Vorup-Jensen

  • C Ostermeier

  • M Shimaoka

  • U Hommel

  • T A Springer

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