Identifying dynamic interactors of protein complexes by quantitative mass spectrometry

Dynamically interacting proteins associate and dissociate with their binding partners at high on/off rates. Although their identification is of great significance to proteomics research, lack of an efficient strategy to distinguish stable and dynamic interactors has hampered the efforts toward this goal. In this work, we developed a new method, MAP (mixing after purification)-SILAC (stable isotope labeling of amino acids in cell culture), to quantitatively investigate the interactions of protein complexes by mass spectrom-etry. In combination with the original SILAC approach, stable and dynamic components were effectively distin-guished by the differences in their relative abundance ratio changes. We applied the newly developed strategies to decipher the dynamics of the human 26 S proteasome-interacting proteins. A total of 67 putative human protea