Ion Mobility-Mass Spectrometry Reveals Long-Lived, Unfolded Intermediates in the Dissociation of Protein Complexes

摘要

Recent applications of mass spectrometry (MS) in structural biology have highlighted its ability to define the stoichiometry of numerous protein complexes. When combined with tandem MS, this extra dimension has made possible 1) analysis of polydisperse assemblies, 2) characterization of release of proteins from within proteasome and chaperone complexes, and 3) identification of proteins released from intact megadalton ribosomes. Tandem MS is effective because macromolecular protein-complex ions decay through a mechanism that involves a dramatic transfer of charge to monomeric subunits prior to their ejection. This asymmetric dissociation acts to distribute the product ion spectrum over a large m/z range, thus enabling separation of ions with overlapping m/z values and identification of heterocomplexes from released subunits.