Fig. 1

Isolation of MAM and its role in phospholipid import into mitochondria. a Rat liver was homogenized and mitochondria (MITO, lower band) were isolated by Percoll gradient ultracentrifugation [19]. The upper band shown on the gel contains the MAM, a specific domain of the ER that has high affinity for mitochondria. b Biosynthesis of phosphatidylserine (PS) and PS import into mitochondria. PS is made via synthase-1 and -2 primarily in the MAM. Newly-made PS is exported from MAM to mitochondria (MITO) and converted therein to phosphatidylethanolamine (PE) via the mitochondrial inner membrane enzyme, PS decarboxylase (PISD). PE is also made in the ER from ethanolamine (Etn) but this source of PE is not readily imported into mitochondria (dotted line)