Cooperative Change in the Internal Dynamics of Streptavidin Caused by Biotin Binding.

Protein-ligand interactions are of vital importance for biological functions. The biological function of proteins, such as ligand-binding, is strongly influenced by their dynamics. Quasielastic neutron scattering (QENS) was used to investigate the internal molecular dynamics of streptavidin (STV). QENS experiments to probe the internal dynamics were performed on a ps and 50-100 ps timescale using inverted geometry time-of-flight spectrometers. At the 50-100 ps timescale, the internal equilibrium motions of streptavidin proved to be unaffected by biotin (B) binding. However, on the ps timescale, suppression of jump-diffusion is observed even upon partial ligand saturation. This change indicates that the entire STV protein was affected by the population of one of the four binding sites, thus supporting a cooperative effect.