Deg/HtrA proteases as components of a network for photosystem II quality control in chloroplasts and cyanobacteria (original) (raw)
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Plant Physiology, 2012
Light energy constantly damages photosynthetic apparatuses, ultimately causing impaired growth. Particularly, the sessile nature of higher plants has allowed chloroplasts to develop unique mechanisms to alleviate the irreversible inactivation of photosynthesis. Photosystem II (PSII) is known as a primary target of photodamage. Photosynthetic organisms have evolved the so-called PSII repair cycle, in which a reaction center protein, D1, is degraded rapidly in a specific manner. Two proteases that perform processive or endopeptidic degradation, FtsH and Deg, respectively, participate in this cycle. To examine the cooperative D1 degradation by these proteases, we engaged Arabidopsis (Arabidopsis thaliana) mutants lacking FtsH2 (yellow variegated2 [var2]) and Deg5/Deg8 (deg5 deg8) in detecting D1 cleaved fragments. We detected several D1 fragments only under the var2 background, using amino-terminal or carboxyl-terminal specific antibodies of D1. The appearance of these D1 fragments was...
Photodamaged D1 protein is degraded in Arabidopsis mutants lacking the Deg2 protease
FEBS letters, 2006
In plants exposed to high irradiances of visible light, the D1 protein in the reaction center of photosystem II is oxidatively damaged and rapidly degraded. Earlier work in our laboratory showed that the serine protease Deg2 performs the primary cleavage of photodamaged D1 protein in vitro. Here, we demonstrate that the rate of D1 protein degradation under light stress conditions in Arabidopsis mutants lacking the Deg2 protease is similar to those in wild-type plants. Therefore, we propose that several redundant D1 protein degradation pathways might exist in vivo.
Structural adaptation of the plant protease Deg1 to repair photosystem II during light exposure
Nature Structural & Molecular Biology, 2011
Deg is a chloroplastic protease involved in maintaining the photosynthetic machinery. Structural and biochemical analyses reveal that the inactive Deg monomer is transformed into the proteolytically active hexamer at acidic pH. The change in pH is sensed by His244, which upon protonation, repositions a specific helix to trigger oligomerization. This system ensures selective activation of Deg during daylight, when acidification of the thylakoid lumen occurs and photosynthetic proteins are damaged.
2007
Deg1 is a Ser protease peripherally attached to the lumenal side of the thylakoid membrane. Its physiological function is unknown, but its localization makes it a suitable candidate for participation in photoinhibition repair by degradation of the photosystem II reaction center protein D1. We transformed Arabidopsis thaliana with an RNA interference construct and obtained plants with reduced levels of Deg1. These plants were smaller than wild-type plants, flowered earlier, were more sensitive to photoinhibition, and accumulated more of the D1 protein, probably in an inactive form. Two C-terminal degradation products of the D1 protein, of 16 and 5.2 kD, accumulated at lower levels compared with the wild type. Moreover, addition of recombinant Deg1 to inside-out thylakoid membranes isolated from the mutant could induce the formation of the 5.2-kD D1 C-terminal fragment, whereas the unrelated proteases trypsin and thermolysin could not. Immunoblot analysis revealed that mutants contain...
Indian journal of biochemistry & biophysics, 2008
The cells of Synechocystis sp. PCC 6803 were subjected under photoinhibitory irradiation (600 micromolm(-2)s(-1)) at various temperatures (20-40 degrees C) to study in vivo quality control of photosystem II (PSII). The protease biogenesis and its consequences on photosynthetic efficiency (chlorophyll fluorescence ratio Fv/Fm) of the PSII, D1 degradation and repair were monitored during illumination and darkness. The loss in Fv/Fm value and degradation of D1 protein occurred not only under high light exposure, but also continued when the cells were subjected under dark restoration process after high light exposure. No loss in Fv/Fm value or D1 degradation occurred during recovery under growth/low light (30 micromol m(-2) s(-1)). Further, it helped the resynthesis of new D1 protein, essential to sustain quality control of PSII. In vivo triggering of D1 protein required high light exposure to switch-on the protease biosynthesis to maintain protease pool which induced temperature-depend...
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2003
A chromatography fraction, prepared from isolated thylakoids of a fatty acid desaturation mutant (Fad6/desADKm r ) of the cyanobacterium Synechocystis 6803, could induce an initial cleavage of the D1 protein in Photosystem II (PSII) particles of Synechocystis 6803 mutant and Synechococcus 7002 wild type as well as in supercomplexes of PSII-light harvesting complex II of spinach. Proteolysis was demonstrated both in darkness and in light as a reduction in the amount of full-length D1 protein or as a production of C-terminal initial degradation fragments. In the Synechocystis mutant, the main degradation fragment was a 10-kDa C-terminal one, indicating an initial cleavage occurring in the cytoplasmic DE-loop of the D1 protein. A protein component of 70 -90 kDa isolated from the chromatographic fraction was found to be involved in the production of this 10-kDa fragment. In spinach, only traces of the corresponding fragment were detected, whereas a 24-kDa C-terminal fragment accumulated, indicating an initial cleavage in the lumenal AB-loop of the D1 protein. Also in Synechocystis the 24-kDa fragment was detected as a faint band. An antibody raised against the Arabidopsis DegP2 protease recognized a 35-kDa band in the proteolytically active chromatographic fraction, suggesting the existence of a lumenal protease that may be the homologue DegP of Synechocystis. The identity of the other protease cleaving the D1 protein in the DE-loop exposed on the stromal (cytoplasmic) side of the membrane is discussed. D
On the molecular mechanism of light-induced D1 protein degradation in photosystem II core particles
Biochemistry, 1992
The mechanism of D1 protein degradation was investigated during photoinhibitory illumination of isolated photosystem I1 core preparations. The studies revealed that a proteolytic activity resides within the photosystem I1 core complex. A relationship between the inhibition of D1 protein degradation and the binding of the highly specific serine protease inhibitor diisopropyl fluorophosphate to isolated complexes of photosystem I1 was observed, evidence that this protease is of the serine type. Using radiolabeled inhibitor, it was shown that the binding site, representing the active serine of the catalytic site, is located on a 43-kDa polypeptide, probably the chlorophyll a protein CP43. The protease is apparently active in darkness, with the initiation of breakdown being dependent on high light-induced substrate activation. The proteolysis, which has an optimum at pH 7.5, gives rise to primary degradation fragments of 23 and 16 kDa. In addition,
Inhibition of the repair of Photosystem II by oxidative stress in cyanobacteria
Photosynthesis Research, 2005
The activity of Photosystem II (PS II) is severely restricted by a variety of environmental factors and, under environmental stress, is determined by the balance between the rate of damage to PS II and the rate of the repair of damaged PS II. The effects of oxidative stress on damage and repair can be examined separately, and it appears that, while light can damage PS II directly, oxidative stress acts primarily by inhibiting the repair of PS II. Studies in cyanobacteria have demonstrated that oxidative stress suppresses the de novo synthesis of proteins, in particular, the D1 protein, which is required for the repair of PS II. Abbreviations: Chl -chlorophyll; DCMU -3-(3,4-dichlorophenyl)-1,1-dimethylurea; P680 -primary electron donor in PS II; PS II -Photosystem II; Q A -the primary electron acceptor of PS II; Q B -the secondary electron acceptor of PS II; ROS -reactive oxygen species Photosynthesis Research (2005) 84: 1-7 Ó Springer 2005
The Plant Cell, 2000
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 substratefunctionally assembled proteins that have undergone irreversible photooxidative damage and cleavage. Vass, I., Styring, S., Hundal, T., Koivuniemi, A., Aro, E.-M., and Andersson, B. (1992). Reversible and irreversible intermediates during photoinhibition of photosystem II: Stable reduces Q A species promote chlorophyll triplet formation. Proc. Natl. Acad. Sci. USA 89, 1408-1412. Zer, H., Prasil, O., and Ohad, I. (1994). Role of plastoquinol oxidoreduction in regulation of photochemical reaction center II D1 protein turnover in vivo.