Proteases are associated with a minor fucoxanthin chlorophyll a/c-binding protein from the diatom, Chaetoceros gracilis

► Proteolysis of PSII and FCPs was observed in PSII and thylakoids from C. gracilis. ► Metalloproteases and serine protease were identified in thylakoids. ► Those proteases were associated with a minor FCP. ► The FCP may play multiple roles in light harvesting and/or protein turnover of PSII.