In vivo quality control of photosystem II in cyanobacteria Synechocystis sp. PCC 6803: D1 protein degradation and repair under the influence of light, heat and darkness (original) (raw)
Related papers
Journal of Plant Physiology, 2005
Photosystem II (PSII) photochemical efficiency (chlorophyll fluorescence ratio Fv/Fm) was recorded in vivo in Synechocystis 6803 during high light illumination and during a subsequent shift of the cells to darkness. A continuing decrease in the Fv/Fm ratio was observed even after the cells were transferred to darkness, provided the temperature was high enough. The decrease in the PSII efficiency after the shifting of the cells to darkness correlated directly with the loss of the D1 protein under different temperatures, suggesting that temperature-dependent proteolysis of the D1 protein in darkness induces the loss of PSII photochemical efficiency under these conditions. Furthermore, the amount of FtsH protease was found to increase during the high light treatment. This observation suggests that the synthesis of the FtsH protein is a lightregulated process and that this protease most probably has a key role in an efficient degradation of the D1 protein even under post-illuminative conditions, provided the temperature is high enough to prevent the initial reversible steps of photoinhibition.
Research in microbiology, 2009
Organisms that perform oxygenic photosynthesis are subjected to photoinhibition of their photosynthetic function when exposed to excessive illumination. The main target of photoinhibition is the D1 protein in the reaction center of the photosystem II complex. Rapid degradation of photodamaged D1 protein and its replacement by a de novo synthesized functional copy represent an important repair mechanism crucial for cell survival under light stress conditions. This review summarizes the literature on the ATP-independent Deg/HtrA family of serine endopeptidases in cyanobacteria and chloroplasts of higher plants, and discusses their role in D1 protein degradation. We propose that Deg/HtrA proteases are part of a larger network of enzymes that ensure protein quality control, including photosystem II, in plants and cyanobacteria.
European Journal of Biochemistry, 1996
The effects of ultraviolet-B radiation (280-320 nm) on photosystem I1 of $JneChoCJJStk sp. PCC 6803 were investigated at the functional and structural levels. Loss of oxygen-evolving and electrontransport activity, measured by various techniques including Clark electrode polarography, fluorescence induction and fluorescence relaxation after a single turnover flash, are discussed in terms of two types of damage caused by ultraviolet-B radiation : (a) depletion of the plastoquinone pool ; (b) perturbation and degradation of the D1 protein, with cleavage in the second transmembrane segment. These findings are in full agreement with those obtained, both in vivo and in vitro for higher plants for which a donor-side mechanism involving the water-splitting Mn cluster has been proposed for the main cleavage of the D1 protein. At the structural level, complete disruption of the photosystem 11 core is documented as a consequence of (or in parallel with) degradation of the D1 protein. From this point of view, ultraviolet-Binduced photoinhibition is unlike the visible-induced type and less susceptible to repair by synthesis and reinsertion of new D1 protein
Journal of Biological Chemistry, 1999
The D1 protein of the photosystem II reaction center is thought to be the most light-sensitive component of the photosynthetic machinery. To understand the mechanisms underlying the light sensitivity of D1, we performed in vitro random mutagenesis of the psbA gene that codes for D1, transformed the unicellular cyanobacterium Synechocystis sp. PCC 6803 with mutated psbA, and selected phototolerant transformants that did not bleach in high intensity light. A region of psbA2 coding for 178 amino acids of the carboxyl-terminal portion of the peptide was subjected to random mutagenesis by low fidelity polymerase chain reaction amplification or by hydroxylamine treatment. This region contains the binding sites for Q B , D2 (through Fe), and P680. Eighteen phototolerant mutants with single and multiple amino acid substitutions were selected from a half million transformants exposed to white light at 320 mol m ؊2 s ؊1. A strain transformed with non-mutagenized psbA2 became bleached under the same conditions. Sitedirected mutagenesis has confirmed that one or more substitutions of amino acids at residues 234, 254, 260, 267, 322, 326, and 328 confers phototolerance. The rate of degradation of D1 protein was not appreciably affected by the mutations. Reduced bleaching of mutant cyanobacterial cells may result from continued buildup of photosynthetic pigment systems caused by changes in redox signals originating from D1.
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
Plant and Cell Physiology
Orange carotenoid protein (OCP) plays a vital role in the thermal dissipation of excitation energy in the photosynthetic machinery of the cyanobacterium Synechocystis sp. PCC 6803. To clarify the role of OCP in the protection of PSII from strong light, we generated an OCP-overexpressing strain of Synechocystis and examined the effects of overexpression on the photoinhibition of PSII. In OCP-overexpressing cells, thermal dissipation of energy was enhanced and the extent of photoinhibition of PSII was reduced. However, photodamage to PSII, as monitored in the presence of lincomycin, was unaffected, suggesting that overexpressed OCP protects the repair of PSII. Furthermore, the synthesis de novo of proteins in thylakoid membranes, such as the D1 protein which is required for the repair of PSII, was enhanced in OCP-overexpressing cells under strong light, while the production of singlet oxygen was suppressed. Thus, the enhanced thermal dissipation of energy via overexpressed OCP might support the repair of PSII by protecting protein synthesis from oxidative damage by singlet oxygen under strong light, with the resultant mitigation of photoinhibition of PSII.
Photosystem II Component Lifetimes in the Cyanobacterium Synechocystis sp. Strain PCC 6803
Journal of Biological Chemistry, 2011
Background: We monitored photosystem II (PSII) protein lifetimes with or without small Cab-like proteins (SCPs) by 15 N labeling and mass spectrometry. Results: Without SCPs, nascent PSII complexes were destabilized, and early chlorophyll precursors were reduced. Conclusion: SCPs play a major role in chlorophyll biosynthesis and nascent PSII stabilization. Significance: Proteins temporarily associated with a protein complex may affect biosynthesis of the complex and cofactors. To gain insight in the lifetimes of photosystem II (PSII) chlorophyll and proteins, a combined stable isotope labeling (15 N)/ mass spectrometry method was used to follow both old and new pigments and proteins. Photosystem I-less Synechocystis cells were grown to exponential or post-exponential phase and then diluted in BG-11 medium with [ 15 N]ammonium and [ 15 N]nitrate. PSII was isolated, and the masses of PSII protein fragments and chlorophyll were determined. Lifetimes of PSII components ranged from 1.5 to 40 h, implying that at least some of the proteins and chlorophyll turned over independently from each other. Also, a significant amount of nascent PSII components accumulated in thylakoids when cells were in post-exponential growth phase. In a mutant lacking small Cab-like proteins (SCPs), most PSII protein lifetimes were unaffected, but the lifetime of chlorophyll and the amount of nascent PSII components that accumulated were decreased. In the absence of SCPs, one of the PSII biosynthesis intermediates, the monomeric PSII complex without CP43, was missing. Therefore, SCPs may stabilize nascent PSII protein complexes. Moreover, upon SCP deletion, the rate of chlorophyll synthesis and the accumulation of early tetrapyrrole precursors were drastically reduced. When [ 14 N]aminolevulinic acid (ALA) was supplemented to 15 N-BG-11 cultures, the mutant lacking SCPs incorporated much more exogenous ALA into chlorophyll than the control demonstrating that ALA biosynthesis was impaired in the absence of SCPs. This illustrates the major effects that nonstoichiometric PSII components such as SCPs have on intermediates and assembly but not on the lifetime of PSII proteins.
Photochemistry and Photobiology, 2000
Plectonema boryanum UTEX 485 cells were grown at 29؇C and 150 mol m Ϫ2 s Ϫ1 photosynthetically active radiation (PAR) and exposed to PAR combined with ultraviolet-A radiation (UV-A) at 15؇C. This induced a timedependent inhibition of photosystem II (PSII) photochemistry measured as a decrease of the chlorophyll a fluorescence ratio, F v /F m , to 50% after 2 h of UV-A treatment compared to nontreated control cells. Exposure of the same cells to PAR combined with UV-A ؉ ultraviolet-B radiation (UV-B) caused only a 30% inhibition of PSII photochemistry relative to nontreated cells. In contrast, UV-A and UV-A ؉ UV-B irradiation of cells cultured at 15؇C and 150 mol m Ϫ2 s Ϫ1 had minimal effects on the F v /F m values. However, cells grown at 15؇C and lower PAR irradiance (6 mol m Ϫ2 s Ϫ1 ) exhibited similar inhibition patterns of PSII photochemistry as control cells. The decreased sensitivity of PSII photochemistry of P. boryanum grown at 15؇C and 150 mol m Ϫ2 s Ϫ1 to subsequent exposure to UV radiation relative to either control cells or cells grown at low temperature but low irradiance was correlated with the following: (1) a reduced efficiency of energy transfer to PSII reaction centers; (2) higher levels of a carotenoid tentatively identified as myxoxanthophyll; (3) the accumulation of scytonemin and mycosporine amino acids; and (4) the accumulation of ATP-dependent caseinolytic proteases. Thus, acclimation of P. boryanum at low temperature and moderate irradiance appears to confer significant resistance to UV-induced photoinhibition of PSII. The role of excitation pressure in the induction of this resistance to UV radiation is discussed.
Influence of High Light Intensity on the Cells of Cyanobacteria Synechocystis Sp. PCC 6803
In this article is presented the result of research regardind the effect of high light intensity on the cells of Anabaena variabilis sp. ATCC 29413, the main objective is to study the adaptation of photosynthetic apparatus to light stress. Samples were analyzed in the present of herbicide diuron (DCMU) which blocks electron flow from photosystem II and without diuron. During treatment maximum fluorescence and photosystems efficiency are significantly reduced, reaching very low values compared with the blank, as a result of photoinhibition installation. Also by this treatment is shown the importance of the mechanisms by which cells detect the presence of light stress and react accordingly.