Does Native Capillary Zone Electrophoresis-Mass Spectrometry Maintain the Structural Topology of Protein Complexes?

Native capillary zone electrophoresis-mass spectrometry (nCZE-MS) is a useful analytical tool for studying protein complexes. However, the extent to which the protein complexes maintain their native structural topology in nCZE-MS compared to traditional native MS (nMS) is still not fully characterized. In this technical note, we contribute to this topic by coupling nCZE-MS with surface-induced dissociation (SID) for two well-studied protein complexes (streptavidin and human recombinant C-reactive protein). SID cleaves the weakest interface of a given complex, making it a powerful diagnostic tool for identifying perturbations of protein complex structures based on fragmentation patterns. The SID fragmentation patterns of the two protein complexes from nCZE-MS under normal and charge-reducing conditions show a high similarity index compared to those from direct infusion. Additionally, nCZE-MS shows the potential to separate different conformations or different proton distributions that have subtle differences. Although only two cases are shown, the results suggest that nCZE-MS can maintain the native-like structural topology of protein complexes.