Carol Robinson has moved to Oxford University

Research Interests Building on our earliest research in which we developed approaches to maintain intact protein complexes in the gas phase we became intrigued by a number of overriding questions: (1) How does a protein complex remain intact in the absence of bulk solvent? (2) What new insight can be gained from studying protein complexes in such an environment? (3) Can we adapt our mass spectrometry (MS) approaches for the study of intact complexes extracted directly from cells? (4) To what extent could we find unknown interactions between macromolecular complexes involved in related processes? These questions form the basis of our research programme.

We have developed MS instrumentation that enables us to maintain large cellular complexes intact or to raise their internal energy to partially dissociate them. These approaches, together with the opportunity to form sub-complexes in solution, have allowed us to establish the complete subunit architecture of the exosome (fig. 1), the molecular machine responsible for degradation of RNA in yeast. Through generation of over 20 different complexes employing three different 'bait' proteins and with no previous experimental data we used computational methods to derive the entire subunit architecture¹.

Having established that the overall subunit composition of numerous complexes is often preserved during transfer from solution to gas phase. A natural progression from the established subunit composition is to investigate the overall shape of these complexes. Since many protein complexes are known to exist in very distinct topologies (eg linear assemblies, rings or solvent excluded close packed conformations) these should be readily distinguished by measurement of the collision cross section. We are developing ion mobility approaches that have previously been restricted to small molecules and individual proteins and applying them to multiprotein complexes. Using a prototype mass spectrometer that enables us to accelerate complexes through a gas filled environment and separate them according to their collision cross section, we have very recently shown that the ring topology of the RNA binding protein TRAP, which assembles into an 11-mer, is maintained for the lowest charge states in the mass spectrum (fig. 2)². Interestingly, using computer simulations, we show that for higher charge states in the mass spectrum, there is evidence for distortion of the ring to buckled rings and collapsed structures.

Selected Publications

1. Hernandez, H., Dziembowski, A., Taverner, T., Seraphin, B. & Robinson, C. V. Subunit architecture of multimeric complexes isolated directly from cells. EMBO Rep 7, 605-10 (2006).
2. Ruotolo, B. T. et al. Evidence for Macromolecular Protein Rings in the Absence of Bulk Water. Science 310, 1658-1661 (2005).