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Structural Characterization of Native Proteins and Protein Complexes by Electron Ionization Dissociation-Mass Spectrometry
journal contribution
posted on 2017-02-07, 00:00 authored by Huilin Li, Yuewei Sheng, William McGee, Michael Cammarata, Dustin Holden, Joseph A. LooMass spectrometry (MS) has played
an increasingly important role
in the identification and structural and functional characterization
of proteins. In particular, the use of tandem mass spectrometry has
afforded one of the most versatile methods to acquire structural information
for proteins and protein complexes. The unique nature of electron
capture dissociation (ECD) for cleaving protein backbone bonds while
preserving noncovalent interactions has made it especially suitable
for the study of native protein structures. However, the intra- and
intermolecular interactions stabilized by hydrogen bonds and salt
bridges can hinder the separation of fragments even with preactivation,
which has become particularly problematic for the study of large macromolecular
proteins and protein complexes. Here, we describe the capabilities
of another activation method, 30 eV electron ionization dissociation
(EID), for the top-down MS characterization of native protein–ligand
and protein–protein complexes. Rich structural information
that cannot be delivered by ECD can be generated by EID. EID allowed
for the comparison of the gas-phase and the solution-phase structural
stability and unfolding process of human carbonic anhydrase I (HCA-I).
In addition, the EID fragmentation patterns reflect the structural
similarities and differences among apo-, Zn-, and Cu,Zn-superoxide
dismutase (SOD1) dimers. In particular, the structural changes due
to Cu-binding and a point mutation (G41D) were revealed by EID-MS.
The performance of EID was also compared to that of 193 nm ultraviolet
photodissociation (UVPD), which allowed us to explore their qualitative
similarities and differences as potential valuable tools for the MS
study of native proteins and protein complexes.