Structure and allosteric regulation of the αXβ2 integrin I domain


Vorup-Jensen, T., Ostermeier, C., Shimaoka, M., Hommel, U. & Springer, T.A. Structure and allosteric regulation of the αXβ2 integrin I domain. Proc Natl Acad Sci USA 100, 4, 1873-1878 (2003).


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.


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Last updated on 09/30/2015