Integrin receptors bind collagen via metal-mediated interactions that are modulated by magnesium (Mg) levels in the extracellular matrix. Nuclear magnetic resonance-based relaxation experiments， isothermal titration calorimetry， and adhesion assays reveal that Mg functions as both a structural anchor and dynamic switch of the αβ integrin I domain (αI). Specifically， Mg binding activates micro- to millisecond timescale motions of residues distal to the binding site， particularly those surrounding the?salt bridge at helix 7 and near the metal ion-dependent adhesion site. Mutagenesis of these residues impacts αI functional activity， thereby suggesting that Mg-bound αI dynamics are important for coll... More
Integrin receptors bind collagen via metal-mediated interactions that are modulated by magnesium (Mg) levels in the extracellular matrix. Nuclear magnetic resonance-based relaxation experiments， isothermal titration calorimetry， and adhesion assays reveal that Mg functions as both a structural anchor and dynamic switch of the αβ integrin I domain (αI). Specifically， Mg binding activates micro- to millisecond timescale motions of residues distal to the binding site， particularly those surrounding the?salt bridge at helix 7 and near the metal ion-dependent adhesion site. Mutagenesis of these residues impacts αI functional activity， thereby suggesting that Mg-bound αI dynamics are important for collagen binding and consequent allosteric rearrangement of the low-affinity closed to high-affinity?open conformation. We propose a multistep recognition mechanism for αI-Mg-collagen interactions involving both conformational selection and induced-fit processes. Our findings unravel the multifaceted role of Mg in integrin-collagen recognition and assist in elucidating the molecular mechanisms by which metals regulate protein-protein interactions.
