Affinity Purification and Coimmunoprecipitation of Transenvelope Protein Complexes in Gram-Negative Bacteria.

Multiprotein complexes are important machineries that organize a large number of different proteins into functional units. Studying protein-protein interactions in the complexes, rather than individual proteins, is a fundamental step to gaining functional insights into a biological process. Here, we present the sequential affinity purification and coimmunoprecipitation system that was applied to enable the efficient purification of all the proteins that compose the Lpt system complex in Escherichia coli and their identification by western blotting and mass spectrometry (MS).