An Iminodiacetic Acid Based Lanthanide Binding Tag for Paramagnetic Exchange NMR Spectroscopy

摘要

When bound to proteins, paramagnetic lanthanide ions induce a range of effects that are observable by NMR spectroscopy, including pseudo-contact shifts (PCSs), paramagnetic relaxation enhancements (PREs), and residual dipolar couplings (RDCs). These effects provide valuable constraints that can expedite protein structure refinement, the analysis of protein-protein and protein-ligand interactions, and, potentially, the study of protein dynamics and lowly populated encounter states of protein complexes. PCSs, measurable for nuclei beyond 60 A away from some lanthanide ions, are especially useful for NMR structural analysis of multidomain proteins and multiprotein complexes. These manifest as changes in chemical shifts between paramagnetic and diamagnetic samples, with the difference in shifts (Δδ~(PCS)) dependent on the location of the nuclear (i.e., ~(15)N and ~(1H)N) spins with respect to the anisotropic magnetic susceptibility tensor (Δχ) of the metal ion: