Immunoprecipitation-Mass Spectrometry (IP-MS) identifies components of a Mce4A-containing complex

How lipids travel between membranes of diderm bacteria is a challenging mechanistic question because lipids, which are hydrophobic molecules, must traverse a hydrophilic periplasm. This question is even more complex for mycobacteria, which have a unique cell envelope that is highly impermeable to molecules. A growing body of knowledge identifies Mce transporters as lipids importers for mycobacteria. Here, using protein stability experiments and immunoprecipitation-mass spectrometry to identify protein interactions among components of the mycobacterial Mce4 transporter we provide evidence for Mce transporters existing as multiprotein complexes.