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Updated: Jun 11, 2026

Static Adhesion Assay for the Study of Integrin Activation in T Lymphocytes
Published on: June 13, 2014
A novel divalent cation-binding site in the A domain of the beta 2 integrin CR3 (CD11b/CD18) is essential for ligand
M Michishita1, V Videm, M A Arnaout
1Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Charlestown 02129.
Abstract:
A recombinant peptide encoding the CD11b A domain bound 54Mn2+ with a high affinity. Other divalent cations, including Mg2+, Zn2+, Ni2+, Co2+, and Cd2+, but not Ca2+ or Ba2+, competed effectively for Mn2+ binding. Amino acid substitutions within two conserved and noncontiguous regions in the recombinant peptide abolished 54Mn2+ binding. When these substitutions were introduced independently in complement receptor type 3 (CR3), each abolished the metal-dependent binding of the receptor to the major C3 opsonin iC3b, without impairing subunit association or surface expression of the receptor. These findings identify an unsuspected and novel metal-binding site within the A domain of CR3 that is required for metal-dependent ligand binding and also identify a good target for designing drugs aimed at countering the inflammatory potential of this key receptor.
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