Mass Spectrometry Characterization of Multiprotein Complexes

INTRODUCTION

Although mass spectrometry measures species in the gas phase, it is becoming widely accepted that, under the appropriate conditions, noncovalent features of protein structure and interactions can be retained in mass spectra. Recent applications have shown that mass spectrometry can provide information not only about the stoichiometry of subunits within a complex, but also about subsets of interacting proteins within macromolecular complexes, the component oligomers in polydisperse assemblies, and changes in quaternary structure in response to phosphorylation of subunits. An important advance in this field has been the recent extension of established techniques to examine protein complexes isolated directly from cells, rather than assembled from recombinant subunits. This protocol provides guidance for setup and use of a mass spectrometer to analyze multiprotein complexes.