In Vivo Protein Cross-Linking and Coimmunoprecipitation in Haloferax volcanii.

Coimmunoprecipitation is a powerful and commonly used method to identify protein-protein interactions in a physiological context. Here, we report a coimmunoprecipitation protocol that was adapted and optimized for the haloarchaeon Haloferax volcanii to identify interacting partners to the LonB protease. This protocol includes the in vivo cross-linking of H. volcanii proteins using two different crosslinker agents, dithiobis(succinimidyl propionate) and formaldehyde, followed by immunoprecipitation with anti-LonB antibody conjugated to Protein A - Sepharose beads. Tryptic on-bead protein digestion was performed combined with Mass Spectrometry analysis of peptides for the identification and quantification of LonB ligands.