Mass spectrometry-enabled structural biology of membrane proteins

The last ∼25 years has seen mass spectrometry (MS) emerge as an integral method in the structural biology toolkit. In particular, MS has enabled the structural characterization of proteins and protein assemblies that have been intractable by other methods, especially those that are large, heterogeneous or transient, providing experimental evidence for their structural organization in support of, and in advance of, high resolution methods. The most recent frontier conquered in the field of MS-based structural biology has been the application of established methods for studying water soluble proteins to the more challenging targets of integral membrane proteins. The power of MS in obtaining structural information has been enabled by advances in instrumentation and the development of hyphenated mass spectrometry-based methods, such as ion mobility spectrometry-MS, chemical crosslinking-MS and other chemical labelling/footprinting-MS methods. In this review we detail the insights garnered into the structural biology of membrane proteins by applying such techniques. Application and refinement of these methods has yielded unprecedented insights in many areas, including membrane protein conformation, dynamics, lipid/ligand binding, and conformational perturbations due to ligand binding, which can be challenging to study using other methods.