Magnesium Activates Microsecond Dynamics to Regulate Integrin-Collagen Recognition

Abstract

Integrin receptors bind collagen via metal-mediated interactions that are modulated by magnesium (Mg 2+ ) levels in the extracellular matrix. Nuclear magnetic resonance-based relaxation experiments, isothermal titration calorimetry, and adhesion assays reveal that Mg 2+ functions as both a structural anchor and dynamic switch of the α 1 β 1 integrin I domain (α 1 I). Specifically, Mg 2+ 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 α 1 I functional activity, thereby suggesting that Mg-bound α 1 I 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 α 1 I-Mg-collagen interactions involving both conformational selection and induced-fit processes. Our findings unravel the multifaceted role of Mg 2+ in integrin-collagen recognition and assist in elucidating the molecular mechanisms by which metals regulate protein-protein interactions. Integrins mediate cellular adhesion via Mg-dependent interactions with collagen. Nunes et al. explore the multifaceted role of Mg 2+ 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.