Abstract
Integrin receptors bind collagen via metal-mediated interactions that are modulated by magnesium (Mg2+) levels in the extracellular matrix. Nuclear magnetic resonance-based relaxation experiments, isothermal titration calorimetry, and adhesion assays reveal that Mg2+ functions as both a structural anchor and dynamic switch of the α1β1 integrin I domain (α1I). Specifically, Mg2+ 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 α1I functional activity, thereby suggesting that Mg-bound α1I 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 α1I-Mg-collagen interactions involving both conformational selection and induced-fit processes. Our findings unravel the multifaceted role of Mg2+ in integrin-collagen recognition and assist in elucidating the molecular mechanisms by which metals regulate protein-protein interactions.
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•Mg2+ binding induces micro- to millisecond dynamics within the integrin α1I domain•Key regions of Mg-bound α1I salt bridge and MIDAS undergo structural fluctuations•The dynamic minor state adopts an intermediate closed-open conformation•α1I-Collagen binding occurs via conformational selection and induced-fit mechanisms
Integrins mediate cellular adhesion via Mg-dependent interactions with collagen. Nunes et al. explore the multifaceted role of Mg2+ as a structural anchor and allosteric regulator by activating μs-ms dynamics that propagate beyond the binding site. These findings provide significant insight into the metal modulated integrin-collagen multistep recognition mechanism.