Characterization of Surface Topology and Binding Area in Complexes of the Elongation Factor Proteins EF‐Ts and EF‐Tu⋅GDP from Thermus thermophilus: A Study by Protein Chemical Modification and Mass Spectrometry

The characterization of protein–protein interactions by means of amino acetylation of lysine residues in combination with mass-spectrometric peptide mapping is described. The differential acetylation pattern for the free proteins (elongation factors EF-Tu and EF-Ts) and the EF-Tu⋅EF-Ts complex was used to characterize structural changes in the effector loop of EF-Tu, and to identify the N-terminal domain of EF-Ts as the major interacting area. The Lys-45 and Lys-52 residues in EF-Tu (shown right) and Lys-21 and Lys-45 residues of EF-Ts were found to be completely shielded from acetylation as a result of complex formation.