Structural Investigation of Proteins and Protein Complexes by Chemical Cross-Linking/Mass Spectrometry

During the last two decades, cross-linking combined with mass spectrometry (MS) has evolved as a valuable tool to gain structural insights into proteins and protein assemblies. Structural information is obtained by introducing covalent connections between amino acids that are in spatial proximity in proteins and protein complexes. The distance constraints imposed by the cross-linking reagent provide information on the three-dimensional arrangement of the covalently connected amino acid residues and serve as basis for de-novo or homology modeling approaches. As cross-linking/MS allows investigating protein 3D-structures and protein-protein interactions not only in-vitro, but also in-vivo, it is especially appealing for studying protein systems in their native environment. In this chapter, we describe the principles of cross-linking/MS and illustrate its value for investigating protein 3D-structures and for unraveling protein interaction networks.