Hydrogen Exchange Mass Spectrometry of Membrane Proteins

Membrane proteins can be divided into two groups, namely peripheral proteins which associate with the broad groups of lipids and integral membrane (transmembrane) proteins which cross the lipid bilayer. Hydrogen exchange mass spectrometry (HX-MS) has been used for a number of years to characterize the conformation and interaction of peripheral membrane proteins with the membrane, in spite of the relative high amount of lipids giving high MS signals. In contrast, integral membrane proteins are usually manipulated with detergents to replace their natural membrane environments. The HX-MS experiment gave on average 72% sequence coverage for bANC1p, but with a much better coverage in the N-terminal half (100%) than in the C-terminal one. A nanodisc is created by encircling phospholipids with membrane scaffold proteins (MSP). The in organello example underscores the importance of studying membrane proteins in an environment as close as possible to their natural one.