The action of cardiolipin on the bacterial translocon.

Cardiolipin is an ever-present component of the energy-conserving inner membranes of bacteria and mitochondria. Its modulation of the structure and dynamism of the bilayer impacts on the activity of their resident proteins, as a number of studies have shown. Here we analyze the consequences cardiolipin has on the conformation, activity, and localization of the protein translocation machinery. Cardiolipin tightly associates with the SecYEG protein channel complex, whereupon it stabilizes the dimer, creates a high-affinity binding surface for the SecA ATPase, and stimulates ATP hydrolysis. In addition to the effects on the structure and function, the subcellular distribution of the complex is modified by the cardiolipin content of the membrane. Together, the results provide rare and comprehensive insights into the action of a phospholipid on an essential transport complex, which appears to be relevant to a broad range of energy-dependent reactions occurring at membranes.