ATP synthase F1 subunit epsilon, mitochondrial is an enzyme that in humans is encoded by the ATP5F1E gene. The protein encoded by ATP5F1E is a subunit of ATP synthase, also known as Complex V. Variations of this gene have been associated with a condition called mitochondrial complex V deficiency, nuclear 3 (MC5DN3) and papillary thyroid cancer.
The ATP5F1E gene, located on the q arm of chromosome 20 in position 13.32, is made up of 3 exons and is 3,690 base pairs in length. The ATP5F1E protein weighs 5.7 kDa and is composed of 51 amino acids. Two pseudogenes of this gene are located on chromosomes 4 and 13.
ATP5F1E is located on the rotating central stalk of ATP synthase, and can be contracted or extended. When it is contracted, it inhibits the ATP synthase active site, preventing ATP from being produced or degraded. It changes shape based on the rotation of the gamma subunit of the stalk, and is also thought to become extended in the presence of ADP, acting as a "safety lock" preventing the wasteful degradation of ATP.