Luminescent Alkyne-Bearing Terbium(III) Complexes and Their Application to Bioorthogonal Protein Labeling.

William I O’Malley,Bim Graham,Gottfried Otting,Michael R Grace,Riccardo Rubbiani,Margaret L Aulsebrook,Leone Spiccia,Choy-Theng Loh,Gilles Gasser,Elwy H Abdelkader,Kellie L Tuck

doi:10.1021/acs.inorgchem.5b02605

William I O’Malley, Bim Graham + Show 9 more

Open Access

https://doi.org/10.1021/acs.inorgchem.5b02605

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Abstract

Two new bifunctional macrocyclic chelate ligands that form luminescent terbium(III) complexes featuring an alkyne group for conjugation to (bio)molecules via the Cu(I)-catalyzed "click" reaction were synthesized. Upon ligation, the complexes exhibit a significant luminescent enhancement when excited at the λ(max) of the "clicked" products. To demonstrate the utility of the complexes for luminescent labeling, they were conjugated in vitro to E. coli aspartate/glutamate-binding protein incorporating a genetically encoded p-azido-L-phenylalanine or p-(azidomethyl)-L-phenylalanine residue. The complexes may prove useful for time-gated assay applications.

Highlights

The site-speci c incorporation of paramagnetic metal ions into proteins allows access to unique NMR parameters that can provide valuable structural insights into protein structure and dynamics.[1,2,3] These include pseudocontact shi s (PCS), residual dipolar couplings (RDC) and paramagnetic relaxation enhancement (PRE)
We report the synthesis of the new tags (C5–C8) and demonstrate their utility in paramagnetic NMR structural studies using human ubiquitin and GB1 as model proteins, as well as the antimicrobial target, HPPK.[45]
We have presented the synthesis of three new lanthanide-binding tags (LBTs) designs

Summary

Introduction

The site-speci c incorporation of paramagnetic metal ions into proteins allows access to unique NMR parameters that can provide valuable structural insights into protein structure and dynamics.[1,2,3] These include pseudocontact shi s (PCS), residual dipolar couplings (RDC) and paramagnetic relaxation enhancement (PRE). The Dc-tensors were determined by tting the measured PCSs (Tables S2 and S3†) to the rst conformer of the NMR structure of ubiquitin (PDB ID 2MJB),[47] both individually for each metal ion (Table 1) and simultaneously for each complex of a given tag with a common metal ion position (Table S4,† vide infra).

Results

Conclusion