Ligand-Capped Cobalt(II) Multiplies the Value of the Double-Histidine Motif for PCS NMR Studies
Wenkai Zhu, Darian T. Yang, Angela M. Gronenborn
Abstract
High Resolution Image Download MS PowerPoint Slide In structural studies by NMR, pseudocontact shifts (PCSs) provide both angular and distance information. For proteins, incorporation of a di-histidine (diHis) motif, coordinated to Co 2+, has emerged as an important tool to measure PCS. Here, we show that using different Co(II)-chelating ligands, such as nitrilotriacetic acid (NTA) and iminodiacetic acid (IDA), resolves the isosurface ambiguity of Co 2+ -diHis and yields orthogonal PCS data sets with different Δχ-tensors for the same diHis-bearing protein. Importantly, such capping ligands effectively eliminate undesired intermolecular interactions, which can be detrimental to PCS studies. Devising and employing ligand-capping strategies afford versatile and powerful means to obtain multiple orthogonal PCS data sets, significantly extending the use of the diHis motif for structural studies by NMR.