Research School of Chemistry, The Australian National University, Canberra, ACT 2601, Australia.
Angew Chem Int Ed Engl. 2018 May 22;57(21):6226-6229. doi: 10.1002/anie.201802501. Epub 2018 Apr 26.
Pseudocontact shifts (PCS) generated by paramagnetic metal ions present valuable long-range information in the study of protein structural biology by nuclear magnetic resonance (NMR) spectroscopy. Faithful interpretation of PCSs, however, requires complete immobilization of the metal ion relative to the protein, which is difficult to achieve with synthetic metal tags. We show that two histidine residues in sequential turns of an α-helix provide a binding site for a Co ion, which positions the metal ion in a uniquely well-defined and predictable location. Exchange between the bound and free cobalt is slow on the timescale defined by chemical shifts, but the NMR resonance assignments are nonetheless readily transferred from the diamagnetic to the paramagnetic NMR spectrum by an I S -exchange experiment. The double-histidine-Co motif offers a straightforward, inexpensive, and convenient way of generating precision PCSs in proteins.
顺磁金属离子产生的赝接触位移（PCS）通过核磁共振（NMR）光谱在蛋白质结构生物学研究中提供了有价值的长程信息。然而，要准确解释 PCS，需要金属离子相对于蛋白质完全固定，这对于合成金属标签来说是很难实现的。我们证明，在α-螺旋的连续转弯处的两个组氨酸残基为 Co 离子提供了一个结合位点，从而将金属离子定位在一个独特的、定义明确且可预测的位置。在由化学位移定义的时间尺度上，结合态和游离态 Co 之间的交换非常缓慢，但通过 I S -交换实验，NMR 共振分配仍然可以很容易地从抗磁 NMR 谱转移到顺磁 NMR 谱。双组氨酸-Co 基序为在蛋白质中产生精确的 PCS 提供了一种简单、经济且方便的方法。
