title: Selective and specific ion binding on proteins at physiologically-relevant concentrations.
abstract: Insoluble proteins dissolved in unsalted water appear to have no well-folded tertiary structures. This raises a fundamental question as to whether being unstructured is due to the absence of salt ions. To address this issue, we solubilized the insoluble ephrin-B2 cytoplasmic domain in unsalted water and first confirmed using NMR spectroscopy that it is only partially folded. Using NMR HSQC titrations with 14 different salts, we further demonstrate that the addition of salt triggers no significant folding of the protein within physiologically relevant ion concentrations. We reveal however that their 8 anions bind to the ephrin-B2 protein with high affinity and specificity at biologically-relevant concentrations. Interestingly, the binding is found to be both salt- and residue-specific.
authors: Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore.
authors: Linlin
authors: L
authors: Miao
authors: Haina
authors: H
authors: Qin
authors: Patrice
authors: P
authors: Koehl
authors: Jianxing
authors: J
authors: Song
mesh_terms: D000595:Amino Acid Sequence; D036388:Ephrin-B2 / Q000737:chemistry* / Q000378:metabolism*; D007477:Ions / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D012492:Salts / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
chemical_list: D036388:Ephrin-B2; D007477:Ions; D012492:Salts; D012996:Solutions; D014867:Water