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Proc Natl Acad Sci U S A. 2002 Oct 29;99(22):14059-64. Epub 2002 Oct 18.

Three-dimensional model of the human platelet integrin alpha IIbbeta 3 based on electron cryomicroscopy and x-ray crystallography.

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The Scripps Research Institute, Department of Cell Biology, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.


Integrins are a large family of heterodimeric transmembrane signaling proteins that affect diverse biological processes such as development, angiogenesis, wound healing, neoplastic transformation, and thrombosis. We report here the three-dimensional structure at 20-A resolution of the unliganded, low-affinity state of the human platelet integrin alpha(IIb)beta(3) derived by electron cryomicroscopy and single particle image reconstruction. The large ectodomain and small cytoplasmic domains are connected by a rod of density that we interpret as two parallel transmembrane alpha-helices. The docking of the x-ray structure of the alpha(V)beta(3) ectodomain into the electron cryomicroscopy map of alpha(IIb)beta(3) requires hinge movements at linker regions between domains in the crystal structure. Comparison of the putative high- and low-affinity conformations reveals dramatic conformational changes associated with integrin activation.

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