we wanted to see where and how the protein p37 interacts with its partner proteins p97, PPI,Sds22 and I3. To this end p37 derivatives with genetically encoded crosslinking amino acid (p-benzoyl-L-phenylalanine) were generated. After incubation with the partner proteins, photocross-linking and tryptic digest the resulting cross-linked peptides were analysed by mass spectrometry.