Role of phosphatidylethanolamine in the biogenesis of mitochondrial outer membrane proteins
26.04.2013
Becker T, Horvath SE, Böttinger L, Gebert N, Daum G, Pfanner N.
J Biol Chem. 2013;288(23):16451-9
The biogenesis of mitochondrial outer membrane proteins involves the activity of protein machines. So far, two different import routes have been described. Proteins with a membrane-spanning beta-barrel are first imported via the translocase of the outer membrane (TOM complex) and then membrane-inserted from the intermembrane space site via the sorting and assembly machinery (SAM complex). In contrast, proteins with alpha-helical membrane spans are directly integrated from the cytosol into the outer mitochondrial membrane. So far, the role of phospholipids in these processes is poorly understood. One of the most abundant phospholipids of the outer mitochondrial membrane is phosphatidylethanolamine (PE). We studied the biogenesis of outer membrane proteins in mitochondria containing a reduced PE content. We found that the import of beta-barrel proteins is delayed, whereas the integration of proteins with alpha-helical membrane anchor is unaffected. In particular, we could show that the initial transport step via the TOM complex is affected. Although the stability of the TOM complex is unaltered it binds to substrate proteins with reduced efficiency upon depletion of PE. We conclude that the TOM complex requires PE for optimal activity.
