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Prof. Dame Carol Robinson

Department of Chemistry, University of Oxford

From peripheral proteins to membrane motors - mass spectrometry comes of age

What can we learn from the study of a protein complex in the gas phase of the mass spectrometer? Aside from the compositional information that is available from obtaining the molecular mass of an intact protein complex, many additional properties can be deduced: these include polydispersity and heterogeneity, which are some of most challenging properties of protein complexes, making them almost impossible to study by conventional structural biology approaches. Mass spectrometry is providing significant insight into protein composition within assemblies by uncovering the effects of post-translational modifications, the dynamics of subunit exchange and changes in interactions in response to small molecule binding. Recent breakthroughs, which combine the study of intact membrane complexes with knowledge of lipid binding sites, is informing both the oligomerisation and downstream coupling of GPCRs. While the majority of these studies of membrane proteins have been performed in detergent micelles very recently we have successfully employed a new means of ionizing proteins directly from membranes. Following sonication of lipid vesicles and application of high electric fields, proteins are effectively drawn out of their native membrane locations into the gas phase of the mass spectrometer. This new approach is revealing many new interactions that have been lost following disruption in detergent micelles.