Magnesium Activates Microsecond Dynamics to Regulate Integrin-Collagen Recognition

• Published in: Structure (London) 2018-08, Vol.26 (8), p.1080-1090.e5
• Main Authors: Nunes, Ana Monica, Minetti, Conceição A.S.A., Remeta, David P., Baum, Jean
• Format: Article
• Language: English
• Subjects: Amino Acid Substitution; Amino Acids - chemistry; Amino Acids - metabolism; Animals; Binding Sites; Cations, Divalent; Cloning, Molecular; collagen interactions; Collagen Type I - chemistry; Collagen Type I - genetics; Collagen Type I - metabolism; conformational selection; CPMG relaxation dispersion; dynamics; Escherichia coli - genetics; Escherichia coli - metabolism; Extracellular Matrix - chemistry; Gene Expression; Genetic Vectors - chemistry; Genetic Vectors - metabolism; Humans; induced fit; Integrin alpha1beta1 - chemistry; Integrin alpha1beta1 - genetics; Integrin alpha1beta1 - metabolism; integrin α1 I domain; Kinetics; Magnesium - chemistry; Magnesium - metabolism; magnesium regulation; metal binding; Models, Molecular; Mutation; NMR spectroscopy; Nuclear Magnetic Resonance, Biomolecular; Protein Binding; Protein Conformation, alpha-Helical; Protein Conformation, beta-Strand; Protein Interaction Domains and Motifs; Rats; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; ZZ exchange
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/j.str.2018.05.010

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. [Display omitted] •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.