A mass spectrometry method for mapping the interface topography of interacting proteins, illustrated by the melittin-calmodulin system.

The shielding of lysine groups from acetylation by acetic anhydride has been used to identify the regions of calmodulin in contact with melittin in the 1:1 complex. The estimation of the degree of acetylation was done by examining cyanogen bromide and cyanogen bromide/trypsin digests by mass spectrometry. Evidence was obtained that lysines-21, -75, and -148 are protected to some extent, with the implication that both the N- and C-terminal lobes and the connecting strand are involved in the interaction.