Electron-capture and electron-transfer dissociation for top-down Fourier-transform mass spectrometry of membrane proteins

摘要

Top-down proteomics uses high-resolution Fourier-transform mass spectrometry (FT-MS) to define proteins by their intact masses in combination with dissociation experiments for unambiguous primary structure determination. It is vital that top-down mass spectrometry address all segments of the proteome, including the integral membrane proteins of biological bilayer membranes that compartmentalize living cells and make up around one third of the proteome and a greater proportion of drug targets. Integral membrane proteins present many technical challenges for efficient mass spectrometry in a large part due to hydrophobic transmembrane domains that limit their solubility in the aqueous solvents usually used for MS analysis. This presentation describes progress in application of electron-capture and electron-transfer dissociation (ECD/ETD), as well as collisionally activated dissociation (CAD), to top-down analysis of membrane proteins. Top-down FT-MS has been applied to the 6 transmembrane domain proton-gated urea channel Urel, the peripheral PSII subunit Psb27 and and the 50 kDa 10 transmembrane domain chloride channel CLC-ec1. The results presented extend the size limit achieved for top-down analysis of integral membrane proteins and raise new considerations for interpretation of ECD/ETD tandem FT-MS data.