Acts as a processive, ATP-dependent zinc metallopeptidase for both cytoplasmic and membrane proteins. Plays a role in the quality control of integral membrane proteins (By similarity). Plays a role in the selective replacement of photosystem II (PSII) protein D1 in the PSII repair cycle following visible-light and UV-B induced damage. If damaged D1 is not removed then new D1 cannot be inserted to restore the PSII reaction center. Seems to also degrade damaged and/or unassembled PSII proteins D2 and PsbB (CP47). May recognize D1 via its first 20 amino acids, as deletion of these prevents the PSII repair cycle. Also seems to degrade cytoplasmic GGPS, glucosylglycerol-phosphate synthase. Binds 1 zinc ion per subunit. Homohexamer (Potential). Part of a large (>500 kDa) complex that includes FtsH3 and PSII. Coimmunoprecipitates with YidC (PubMed:30061392). A fraction is found associated with PSII. Localization to the cell inner membrane has been specifically tested and not seen. By UV-B light and oxidative stress provided by methyl viologen. Cells have decreased chlorophyll content, with a 60% reduction in the content of photosystem I (PSI). The PSI that remains may have an altered structure. Cells grow normally under very low light (10 umol photons/m(2)/s) but are dramatically inhibited by low light at 40 umol photons/m(2)/s. Under this light intensity they also photobleach. Reduced rates of D1 processing and degradation are observed. Mutants show increased tolerance for non-ionic stress by maltose but also an increased sensitivity to high NaCl concentrations. In the central section; belongs to the AAA ATPase family. In the C-terminal section; belongs to the peptidase M41 family.