Noncovalent Tagging Proteins with Paramagnetic Lanthanide Complexes for Protein Study

Abstract

The site-specific labeling of proteins with paramagnetic lanthanides offers unique opportunities for NMR spectroscopic analysis in structural biology. Herein, we report an interesting way of obtaining paramagnetic structural restraints by employing noncovalent interaction between a lanthanide metal complex, [Ln(L)3](n-) (L=derivative of dipicolinic acid, DPA), and a protein. These complexes formed by lanthanides and DPA derivatives, which have different substitution patterns on the DPA derivatives, produce diverse thermodynamic and paramagnetic properties when interacting with proteins. The binding affinity of [Ln(L)3](n-) with proteins, as well as the determined paramagnetic tensor, are tunable by changing the substituents on the ligands. These noncovalent interactions between [Ln(L)3](n-) and proteins offer great opportunities in the tagging of proteins with paramagnetic lanthanides. We expect that this method will be useful for obtaining multiple angles and distance restraints of proteins in structural biology.

Bioconjugation of Proteins with a Paramagnetic NMR and Fluorescent Tag

“…A few peaks showed obvious chemical-shift changes and decreased peak intensity, which probably stem from noncovalent inter- 3 ] 3À and the protein. [15] This competition experiment suggests that 4MTDA-tagged protein forms highly stable lanthanide complexes in aqueous solution (Supporting Information, Figure S3).…”

An encodable lanthanide binding tag with reduced size and flexibility for measuring residual dipolar couplings and pseudocontact shifts in large proteins

“…Paramagnetic metals can occur naturally in a macromolecule (Butler 1998; Sjodt et al 2015) or be introduced by replacing an existing metal (Keniry et al 2006), covalently or non-covalently added as a chelate (Huang et al 2013; Lee et al 2015; Loh et al 2015; Wei et al 2013; Yang et al 2015), bound by an unnatural amino acid (Loh et al 2013; Park et al 2015), or lanthanide-binding peptide sequence tag (LBT) engineered into the protein sequence (Barthelmes et al 2011; Feeney et al 2001; Gaponenko et al 2000; Martin and Imperiali 2015; Nitz et al 2003; Su et al 2008), to reference a few key examples. One common limitation to artificial tags is the presence of metal ion motion.…”

Luminescent and Chiroptical Properties of 1 : 1 Eu (III) : Tetracycline Species Probed by Circularly Polarized Luminescence

“…It can be seen that the dimethylamino group lies above the BCD ring system in order to relieve the steric crowding between the protonated nitrogen of the dimethylamino group and its neighboring hydroxyl group (Scheme ). On the other hand, a shift of the equilibrium to the extended conformation is observed when basic and nonaqueous solution conditions are used . In this extended conformation, the dimethylamino group lies below the plane of the BCD ring system.…”

“…Several studies using NMR, CD, absorption and fluorescence spectroscopy, as well as electroanalytical methods, were devoted to the investigation on the relatively complicated decomplexation pattern of TC and its numerous possible chelation sites. These studies were conducted using various metal ions in aqueous and organic media . The structure of TC defines the complexation behavior with metal ions that, ultimately, determines largely their biological action and pharmacokinetic properties.…”