Cross-linking/Mass Spectrometry Combined with Ion Mobility on a timsTOF Pro Instrument for Structural Proteomics

The combination of cross-linking/mass spectrometry (XL-MS) and ion mobility is still underexplored for conducting protein conformational and protein-protein interaction studies. We present a method for analyzing cross-linking mixtures on a timsTOF Pro mass spectrometer that allows separating ions based on their gas phase mobilities. Cross-linking was performed with three urea-based MS-cleavable cross-linkers that deliver distinct fragmentation patterns for cross-linked species upon collisional activation. The discrimination of cross-linked species from non-cross-linked peptides was readily performed based on their collisional cross sections. We demonstrate the general feasibility of our combined XL-MS/ion mobility approach for three protein systems of increasing complexity: (i) Bovine serum albumin, (ii) E. coli ribosome, and (iii) HEK293T cell nuclear lysates. We identified a total of 508 unique cross-linking sites for BSA, 868 for the E. coli ribosome, and 1,623 unique cross-links for nuclear lysates, corresponding to 1,088 intra- and 535 interprotein interactions and yielding 564 distinct protein-protein interactions. Our results underline the strength of combining XL-MS with ion mobility not only for deriving 3D-structures of single proteins, but also for performing system-wide protein interaction studies. TOC Graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=105 SRC="FIGDIR/small/437136v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@141c418org.highwire.dtl.DTLVardef@b13483org.highwire.dtl.DTLVardef@1eeb0ecorg.highwire.dtl.DTLVardef@1a15c12_HPS_FORMAT_FIGEXP M_FIG C_FIG