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Updated: Jul 31, 2026
09:14
Static Adhesion Assay for the Study of Integrin Activation in T Lymphocytes
Published on: June 13, 2014
Cation binding to the integrin CD11b I domain and activation model assessment
E T Baldwin1, R W Sarver, G L Bryant
1Structural, Analytical & Medicinal Chemistry, Pharmacia & Upjohn, Inc., Kalamazoo, MI 49001, USA. eric.t.baldwin@am.pnu.com
Structure (London, England : 1993)
|August 4, 1998
Summary
The CD11b I domain
Area of Science:
- Structural biology
- Biochemistry
- Cell adhesion
Background:
- Integrins are cell-surface receptors mediating cell adhesion.
- The CD11b I domain is crucial for integrin function, binding divalent metal ions.
- Previous studies proposed distinct active/inactive conformations for the CD11b I domain upon receptor binding.
Purpose of the Study:
- To independently determine the X-ray structure of the CD11b I domain.
- To evaluate the structural impact of divalent ion binding on the CD11b I domain.
Main Methods:
- X-ray crystallography of the CD11b I domain.
- Multiple Isomorphous Replacement (MIR) for structure determination.
- Titration calorimetry for determining ion binding constants.
Main Results:
- The crystal structure of the CD11b I domain was determined in the absence of metal ions.
- Divalent cation binding at the MIDAS site did not alter the overall protein conformation.
- The observed conformation is consistent with previously reported CD11a and CD11b I-domain structures.
Conclusions:
- Mg2+, Mn2+, and Cd2+ binding does not induce conformational changes in the CD11b I domain.
- Poor Ca2+ binding explains its failure to support adhesion.
- The proposed 'active' conformation is likely an artifact; no dramatic structural transition occurs during binding.
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