A single-molecule dissection of ligand binding to a protein with intrinsic dynamics.

Protein dynamics have been suggested to have a crucial role in biomolecular recognition, but the precise molecular mechanisms remain unclear. Herein, we performed single-molecule fluorescence resonance energy transfer measurements for wild-type maltose-binding protein (MBP) and its variants to demonstrate the interplay of conformational dynamics and molecular recognition. Kinetic analysis provided direct evidence that MBP recognizes a ligand through an 'induced-fit' mechanism, not through the generally proposed selection mechanism for proteins with conformational dynamics such as MBP. Our results indicated that the mere presence of intrinsic dynamics is insufficient for a 'selection' mechanism. An energetic analysis of ligand binding implicated the critical role of conformational dynamics in facilitating a structural change that occurs upon ligand binding.