Abstract

Compared to our knowledge of protein secondary and tertiary structure, the driving forces behind protein quaternary structure are poorly understood. Over the past three years, our group has been using ion mobility separation, a tool that can separate proteins by virtue of their orientationally-averaged size in the gas phase, in combination with mass spectrometry to probe the influence of bulk solvent on the stability of protein quaternary structure. In our experiments we have observed evidence both of topologies that match what is known about protein assemblies in solution as well as discrete structural transitions that are only generated in the absence of bulk solvent. In this presentation, the gas-phase quaternary structures and structural transitions of protein assemblies that cover a range of known topologies in solution will be discussed. This discussion will ultimately focus toward our long-term efforts to integrate ion mobility and mass spectrometry data in order to determine the topology and architecture of unknown protein complexes.