Phosphatidylcholine affects inner membrane protein translocases of mitochondria
Schuler MH, Di Bartolomeo F, Mårtensson CU, Daum G, Becker T.
The majority of mitochondrial precursor proteins are imported via the translocase of the outer membrane (TOM complex) and transferred to inner membrane-bound protein translocases. The presequence translocase (TIM23 complex) sorts presequence-containing proteins into the inner membrane and promotes in collaboration with the presequence translocase-associated motor transport into the mitochondrial matrix. The carrier translocase (TIM22 complex) inserts proteins with multiple transmembrane domains that lack such a cleavable presequence. Both transport pathways are driven by the membrane potential, which is generated by the respiratory chain. Previous studies revealed that phospholipids like phosphatidylethanolamine and cardiolipin are important to maintain full activity of the respiratory chain. Here, we analyzed the role of phosphotidylcholine for protein transport into and across the inner membrane. In contrast to phosphatidylethanolamine and cardiolipin depletion of phosphatidylcholine does not affect the respiratory chain and the membrane potential. Instead the import step is defective at the stage of the inner membrane protein translocases. Thus, phospholipids differentially affect protein transport into mitochondria.
