A mutation in ATP5E (ATP synthase, H+ transporting, mitochondrial F1 complex, epsilon subunit) was identified in an Austrian woman with complex V deficiency,133 and a single gene defect has been identified in the complex V assembly factor gene ATPAF2, resulting in impaired complex V activity.134. Here, ATP5F1E is linked to hyperinsulinemic hypoglycemia, familial, 4.