A glimpse into the molecular mechanism of integral membrane proteins through hydrogen-deuterium exchange mass spectrometry.

Integral membrane proteins (IMPs) control countless fundamental biological processes and constitute the majority of drug targets. For this reason, uncovering their molecular mechanism of action has long been an intense field of research. They are, however, notoriously difficult to work with, mainly due to their localization within the heterogeneous of environment of the biological membrane and the instability once extracted from the lipid bilayer. High-resolution structures have unveiled many mechanistic aspects of IMPs but also revealed that the elucidation of static pictures has limitations. Hydrogen-deuterium exchange coupled to mass spectrometry (HDX-MS) has recently emerged as a powerful biophysical tool for interrogating the conformational dynamics of proteins and their interactions with ligands. Its versatility has proven particularly useful to reveal mechanistic aspects of challenging classes of proteins such as IMPs. This review recapitulates the accomplishments of HDX-MS as it has matured into an essential tool for membrane protein structural biologists.