Part of a complex that function as an ATP-dependent zinc metallopeptidase. Involved in the thylakoid formation and in the removal of damaged D1 in the photosystem II, preventing cell death under high-intensity light conditions. Not involved in the degradation of the light-harvesting complex of photosystem II (LHC II) or in thermotolerance. Binds 1 zinc ion per subunit. Heterohexamers with FTSH1, FTSH2 and FTSH8. Ubiquitous. Low expression in cotyledons, increasing with leaves development. By high light. Leaf-variegated. Mutations can be complemented by overexpression of FTSH1. The presence of both FTSH1 or FTSH5 (subunit type A) and FTSH2 or FTSH8 (subunit type B) is essential for an active complex formation. In the N-terminal section; belongs to the AAA ATPase family. In the C-terminal section; belongs to the peptidase M41 family.