GB1与金属离子相互作用的NMR研究

G群链球菌G蛋白的B1结构域——GB1蛋白，常被用作发展体外及体内基于顺磁核磁共振（NMR）的蛋白质结构测定方法的研究模型.为确保赝接触化学位移（PCS）、顺磁弛豫增强（PRE）等顺磁约束数据的准确性，了解GB1和金属离子，尤其是顺磁离子的相互作用非常必要.然而GB1和二价金属离子以及镧系金属离子的相互作用并不十分清楚.本文利用NMR波谱研究了GB1和镧系金属离子以及多种二价金属离子的相互作用.我们发现GB1和镧系金属离子之间存在弱特异性相互作用，和Mn²⁺、Cu²⁺以及Co²⁺等顺磁二价离子弱结合，但不与Ca²⁺、Mg²⁺以及Zn²⁺等抗磁二价离子结合.该研究表明在GB1上链接顺磁探针时，应使用与固有位点结合常数差异明显的顺磁标签以获取正确的PRE数据.

Interaction of GB1 with Metal Ions Studied by NMR Spectroscopy

B1 domain of staphylococcal protein G (GB1) is a widely used model protein for developing in vivo and in vitro protein structural determination methods based on paramagnetic nuclear magnetic resonance (NMR) such as pseudocontact chemical shift (PCS) and paramagnetic relaxation enhancement (PRE).However,few previous studies have investigated the interactions between GB1 and metal ions,especially paramagnetic ions.In this study,the interactions between GB1 and divalent/lanthanide metal ions were studied by NMR spectroscopy.It was found that GB 1 weakly bound with paramagnetic lanthanide ions and paramagnetic divalent ions,including Cu2+,Mn2+ and Co2+.In contrast,GB1 did not bind with diamagnetic divalent ions,such as Ca2+,Mg2+ and Zn2+.Furthermore,it was demonstrated that there were two binding sites for Cu2+ in GB 1,but only one for lanthanide ions and divalent ions Mn2+ and Co2+.The current study demonstrated that NMR spectroscopy is a powerful tool to study weak binding between protein and metal ions.And the results indicated that care must be taken to avoid possible interference to paramagnetic NMR data when using GB 1 as the model protein.