Detection of a Protein Conformational Equilibrium by Electrospray Ionisation-Ion Mobility-Mass Spectrometry

摘要

Ion mobility spectrometry (IMS) is emerging as a promising technique for providing low-resolution protein-structure information, particularly in combination with electrospray ionization (ESI) and mass spectrometry (MS). There is currently much debate on the structure of protein ions in the gas phase, as summarized by Breuker and McLafferty. Whilst it appears probable that some structural collapse occurs within picoseconds of dehydration, the onset of gross structural rearrangement may require tens of milliseconds.This time provides a potential window for the observation of "near-native" structures that may retain some elements of the solution structure, with the ability to provide biologically relevant information. A number of recent applications have used IMS to study the conformation and stoichiometry of proteins and their complexes. Structural changes to amyloid and prion proteins, as well as steps in amyloid fibril assembly, have been detected by using this approach, and the calcium-dependent conformational change in calmodulin has been probed by IM-MS, as has the relationship between tertiary structure and chemotactic activity in antibacterial peptides. Insights into the structures of large multiprotein complexes, such as the RNA-binding TRAP protein, GroEL, and the 20S proteasome have also been provided by ion mobility measurements.