Department of Chemistry & Chemical Biology, Rutgers University, 610 Taylor Road, Piscataway, NJ 08854, USA; Center for Integrative Proteomics Research, Rutgers University, 174 Frelinghuysen Road, Piscataway, NJ 08854, USA.
Department of Chemistry & Chemical Biology, Rutgers University, 610 Taylor Road, Piscataway, NJ 08854, USA.
Structure. 2018 Aug 7;26(8):1080-1090.e5. doi: 10.1016/j.str.2018.05.010. Epub 2018 Jun 21.
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.
整合素受体通过金属介导的相互作用与胶原蛋白结合，这种相互作用受细胞外基质中镁 (Mg) 水平的调节。基于核磁共振的弛豫实验、等温滴定量热法和黏附实验表明，Mg 不仅是 αβ 整合素 I 结构域 (αI) 的结构锚点，还是其动态开关。具体来说，Mg 结合激活了结合位点远端的微秒至毫秒时间尺度的残基运动，特别是那些围绕着 7 号螺旋的以及靠近金属离子依赖黏附位点的残基。这些残基的突变会影响 αI 的功能活性，这表明 Mg 结合的 αI 动力学对于胶原蛋白结合以及随后低亲和力的封闭构象向高亲和力的开放构象的变构重排是重要的。我们提出了一个涉及构象选择和诱导契合过程的 αI-Mg-胶原蛋白相互作用的多步骤识别机制。我们的发现揭示了 Mg 在整合素-胶原蛋白识别中的多方面作用，并有助于阐明金属调节蛋白质-蛋白质相互作用的分子机制。
