title: Site-specific tagging proteins with a rigid, small and stable transition metal chelator, 8-hydroxyquinoline, for paramagnetic NMR analysis.
abstract: Design of a paramagnetic metal binding motif in a protein is a valuable way for understanding the function, dynamics and interactions of a protein by paramagnetic NMR spectroscopy. Several strategies have been proposed to site-specifically tag proteins with paramagnetic lanthanide ions. Here we report a simple approach of engineering a transition metal binding motif via site-specific labelling of a protein with 2-vinyl-8-hydroxyquinoline (2V-8HQ). The protein-2V-8HQ adduct forms a stable complex with transition metal ions, Mn(II), Co(II), Ni(II), Cu(II) and Zn(II). The paramagnetic effects generated by these transition metal ions were evaluated by NMR spectroscopy. We show that 2V-8HQ is a rigid and stable transition metal binding tag. The coordination of the metal ion can be assisted by protein sidechains. More importantly, tunable paramagnetic tensors are simply obtained in an α-helix that possesses solvent exposed residues in positions i and i + 3, where i is the residue to be mutated to cysteine, i + 3 is Gln or Glu or i - 4 is His. The coordination of a sidechain carboxylate/amide or imidazole to cobalt(II) results in different structural geometries, leading to different paramagnetic tensors as shown by experimental data.
authors.affiliation: State Key Laboratory of Elemento-Organic Chemistry, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin, 300071, China.
authors.forename: Yin
authors.initials: Y
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Elemento-Organic Chemistry, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin, 300071, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Huang
authors.affiliation: Research School of Chemistry, Australian National University, Canberra, ACT, 0200, Australia.
authors.forename: Thomas
authors.initials: T
authors.lastname: Huber
authors.affiliation: State Key Laboratory of Elemento-Organic Chemistry, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin, 300071, China. xunchengsu@nankai.edu.cn.
authors.forename: Xun-Cheng
authors.initials: XC
authors.lastname: Su
mesh_terms: D000818:Animals; D002614:Chelating Agents / Q000737:chemistry*; D006801:Humans; D019906:Nuclear Magnetic Resonance, Biomolecular; D015125:Oxyquinoline / Q000737:chemistry*; D025801:Ubiquitin / Q000737:chemistry*
chemical_list: D002614:Chelating Agents; D025801:Ubiquitin; D015125:Oxyquinoline
keywords: 8-Hydroxyquinoline; Paramagnetic NMR spectroscopy; Paramagnetic relaxation enhancement; Protein labeling; Pseudocontact shift