ATP5F1A and Mitochondrial encephalopathy: ATP5A1, also known ATP Synthase F1 Subunit Alpha, is a nuclear gene encoding a mitochondrial protein and a mitochondrial membrane ATP synthase, which is a crucial part of complex V. In humans, an ATP5A1 mutation leads to fatal neonatal mitochondrial encephalopathy, and complementation of the ATP5A1 defect restores the amount and activity of complex V16.