Structure of an integrin with an αI domain, complement receptor type 4
Open Access
- 24 December 2009
- journal article
- Published by Springer Science and Business Media LLC in The EMBO Journal
- Vol. 29 (3), 666-679
- https://doi.org/10.1038/emboj.2009.367
Abstract
We report the structure of an integrin with an αI domain, αXβ2, the complement receptor type 4. It was earlier expected that a fixed orientation between the αI domain and the β‐propeller domain in which it is inserted would be required for allosteric signal transmission. However, the αI domain is highly flexible, enabling two βI domain conformational states to couple to three αI domain states, and greater accessibility for ligand recognition. Although αXβ2 is bent similarly to integrins that lack αI domains, the terminal domains of the α‐ and β‐legs, calf‐2 and β‐tail, are oriented differently than in αI‐less integrins. Linkers extending to the transmembrane domains are unstructured. Previous mutations in the β2‐tail domain support the importance of extension, rather than a deadbolt, in integrin activation. The locations of further activating mutations and antibody epitopes show the critical role of extension, and conversion from the closed to the open headpiece conformation, in integrin activation. Differences among 10 molecules in crystal lattices provide unprecedented information on interdomain flexibility important for modelling integrin extension and activation.Keywords
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