The Thylakoid FtsH Protease Plays a Role in the Light-Induced Turnover of the Photosystem II D1 Protein

Abstract

The photosystem II reaction center D1 protein is known to turn over frequently. This protein is prone to irreversible damage caused by reactive oxygen species that are formed in the light; the damaged, nonfunctional D1 protein is degraded and replaced by a new copy. However, the proteases responsible for D1 protein degradation remain unknown. In this study, we investigate the possible role of the FtsH protease, an ATP-dependent zinc metalloprotease, during this process. The primary light-induced cleavage product of the D1 protein, a 23-kD fragment, was found to be degraded in isolated thylakoids in the dark during a process dependent on ATP hydrolysis and divalent metal ions, suggesting the involvement of FtsH. Purified FtsH degraded the 23-kD D1 fragment present in isolated photosystem II core complexes, as well as that in thylakoid membranes depleted of endogenous FtsH. In this study, we definitively identify the chloroplast protease acting on the D1 protein during its light-induced turnover. Unlike previously identified membrane-bound substrates for FtsH in bacteria and mitochondria, the 23-kD D1 fragment represents a novel class of FtsH substrate-functionally assembled proteins that have undergone irreversible photooxidative damage and cleavage.

Coordinated Regulation and Complex Formation of YELLOW VARIEGATED1 and YELLOW VARIEGATED2, Chloroplastic FtsH Metalloproteases Involved in the Repair Cycle of Photosystem II in Arabidopsis Thylakoid Membranes

“…Subsequently, the latter's involvement in the degradation of unassembled thylakoid proteins was suggested (Ostersetzer and Adam, 1997). Later, the product of FtsH1 cDNA, when expressed as a soluble fusion protein, was shown to participate in vitro in the degradation of photodamaged D1 protein of the photosystem (PS) II reaction center (Lindahl et al, 2000). A notable observation is that, in contrast to other organisms such as yeast and humans, higher plants contain an extraordinary number of FtsH homologs (Adam et al, 2001;Ogura and Wilkinson, 2001;Sokolenko et al, 2002).…”

Membrane Proteomic Analysis of Arabidopsis thaliana Using Alternative Solubilization Techniques

“…FtsH proteases are found in chloroplasts as integral proteins within the thylakoid membrane, with their ATP-binding domain and catalytic zinc-binding site facing the stroma. 55,56 There are 9 members in the FtsH protease family in Arabidopsis of which we identified four, each containing one TMD: FtsH1 (At1g50250), FtsH2 (At2g30950), FtsH4 (At2g26140), and FtsH8 (At1g06430). Three of our identifications were obtained using methanol (Tables 2 and 3) and one with the Brij-58 method (Table 2).…”

The Thylakoid Lumen Protease Deg1 Is Involved in the Repair of Photosystem II from Photoinhibition in Arabidopsis

“…Although D1 degradation has been characterized for the past two decades, the first insights into the identity of the proteases involved have only been obtained in recent years. In vitro and in vivo studies have suggested that the FtsH protease participates in this process (Lindahl et al, 2000;Bailey et al, 2002;Sakamoto et al, 2002).…”