This family constitutes the mitochondrial ATP synthase epsilon subunit. This is not to be confused with the bacterial epsilon subunit, which is homologous to the mitochondrial delta subunit (Pfam:PF00401 and Pfam:PF02823) The epsilon subunit is located in the extrinsic membrane section F1, which is the catalytic site of ATP synthesis. The epsilon subunit was not well ordered in the crystal structure of bovine F1 [1], but it is known to be located in the stalk region of F1 [2]. E subunit is thought to be involved in the regulation of ATP synthase, since a null mutation increased oligomycin sensitivity and decreased inhibition by inhibitor protein IF1 [2].

1: Structure at 2.8 A resolution of F1-ATPase from bovine heart mitochondria. Abrahams JP, Leslie AG, Lutter R, Walker JE; Nature 1994;370:621-628. PMID:8065448

2: Cloning, characterization and mapping of the human ATP5E gene, identification of pseudogene ATP5EP1, and definition of the ATP5E motif. Tu Q, Yu L, Zhang P, Zhang M, Zhang H, Jiang J, Chen C, Zhao S; Biochem J 2000;347:17-21. PMID:10727396