"Dark Mediators" of Proteins as Revealed by NMR in Water: Residue-selective Anion Bindings that are Masked by Pre-existing Buffer

Abstract

Ions are commonly believed to impose their effects on proteins by unspecific electrostatic screening. Here, by NMR we reveal that in water sulfate, chloride and thiocyanate are able to bind a well-folded WW domain at distinctive residues and affinities, which is surprisingly masked by the pre-existing buffer. Our study reveals that the specific anion binding is so ubiquitous and consequently no longer negligible in establishing "postreductionist framework" for protein biochemistry.