Thylakoid protein phosphorylation during State 1—State 2 transitions in osmotically shocked pea chloroplasts (original) (raw)
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Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1986
The kinetics of LHCP phosphorylation and associated changes in photosystem cross-section and energy 'spill-over' from PS II to PS I have been examined in isolated spinach chloroplasts. During an initial phosphorylation period of 3-6 min, in the presence of saturating concentrations of Mg 2+, the increase in PS I and decrease in PS II cross-section are largely completed, as judged by both measurements of the steady-state redox state of Q and fluorescence yield changes. This corresponds to a period of rapid 32p incorporation into the low-molecular weight LHCP polypeptide. Subsequent to this initial 3-6-min period there is substantial further phospborylation of both LHCP polypeptides, which is not accompanied by significant changes in photosystem cross-section, even after the chloroplasts had been unstacked with extensive mixing of PS I and PS II by Mg-removal. It is suggested that there exists a specific 'mobile' population of LHCP molecules which is rapidly phosphorylated and which may be enriched in the low-molecular-weight polypeptide. In addition, measurements of the kinetics of the 'spill-over' changes upon either Mg 2+ addition or removal indicate that the continued phosphorylation of LHCP is able to increase the 'spill-over' process under favourable ionic conditions.
Planta, 2015
Main conclusion Light quality has various effects on photochemistry and protein phosphorylation in Zea mays and Arabidopsis thaliana thylakoids due to different degrees of light penetration across leaves and redox status in chloroplasts. The effect of the spectral quality of light (red, R and far red, FR) on the function of thylakoid proteins in Zea mays and Arabidopsis thaliana was investigated. It was concluded that red light stimulates PSII activity in A. thaliana thylakoids and in maize bundle sheath (BS) thylakoids, but not in mesophyll (M) thylakoids. The light quality did not change PSI activity in M thylakoids of maize. FR used after a white light period increased PSI activity significantly in maize BS and only slightly in A. thaliana thylakoids. As shown by blue native (BN)-PAGE followed by SDS-PAGE, proteins were differently phosphorylated in the thylakoids, indicating their different functions. FR light increased dephosphorylation of LHCII proteins in A. thaliana thylakoids, whereas in maize, dephosphorylation did not occur at all. The rate of phosphorylation was higher in maize BS than in M thylakoids. D1 protein phosphorylation increased in maize and decreased in A. thaliana upon irradiation with both R and growth light (white light, W). Light variations did not change the level of proteins in thylakoids. Our data strongly suggest that response to light quality is a species-dependent phenomenon. We concluded that the maize chloroplasts were differently stimulated, probably due to different degrees of light penetration across the leaf and thereby the redox status in the chloroplasts. These acclimation changes induced by light quality are important in the regulation of chloroplast membrane flexibility and thus its function. Keywords Acclimation to light quality Á Bundle sheath chloroplasts Á Mesophyll chloroplasts Á PSI Á PSII Á Protein phosphorylation Á Red and far red light Á Thylakoids Abbreviations BS Bundle sheath BN-PAGE Blue native electrophoresis CET Cyclic electron transport FR Far red light LHCII Chlorophyll a/b-binding protein of photosystem II M Mesophyll R Red light W White light & El_ zbieta Romanowska
FEBS Letters, 1984
Protein phosphorylation in isolated, intact pea chloroplasts was measured during the onset of CO2‐dependent O2 evolution. Total incorporation of 32P (from 32Pi) into the light‐harvesting chlorophyll a/b—protein was found to be less sensitive than O2 evolution to inhibition by the uncouplers FCCP and NH4C1 It is concluded that changes in the rate of ATP synthesis cannot affect protein phosphorylation without also affecting the rate of CO2‐fixation in this system. The ATP/ADP ratio is therefore unlikely to regulate photosynthetic protein phosphorylation under normal physiology conditions.
Biochimica Et Biophysica Acta-bioenergetics, 2008
Phosphorylation-dependent movement of the light-harvesting complex II (LHCII) between photosystem II (PSII) and photosystem I (PSI) takes place in order to balance the function of the two photosystems. Traditionally, the phosphorylatable fraction of LHCII has been considered as the functional unit of this dynamic regulation. Here, a mechanical fractionation of the thylakoid membrane of Spinacia oleracea was performed from leaves both in the phosphorylated state (low light, LL) and in the dephosphorylated state (dark, D) in order to compare the phosphorylation-dependent protein movements with the excitation changes occurring in the two photosystems upon LHCII phosphorylation. Despite the fact that several LHCII proteins migrate to stroma lamellae when LHCII is phosphorylated, no increase occurs in the 77 K fluorescence emitted from PSI in this membrane fraction. On the contrary, such an increase in fluorescence occurs in the grana margin fraction, and the functionally important mobile unit is the PSI-LHCI complex. A new model for LHCII phosphorylation driven regulation of relative PSII/PSI excitation thus emphasises an increase in PSI absorption cross-section occurring in grana margins upon LHCII phosphorylation and resulting from the movement of PSI-LHCI complexes from stroma lamellae and subsequent co-operation with the P-LHCII antenna from the grana. The grana margins probably give a flexibility for regulation of linear and cyclic electron flow in plant chloroplasts.
Journal of plant physiology, 1993
The half-time (r,J of the Mi+ induced chlorophyll fluorescence rise in pea thylakoid membranes increases at elevated temperatures, the maximal effect being observed at 45°C. It was also observed that the half-time of fluorescence rise decreased by increasing the Mi+ concentration in both control and heat treated chloroplasts, but the r~values of heat stressed membranes remain higher than in control (nonheated) preparations at all Mi+ concentrations tested (1-10 mM). The second effect of thermal treatment was to change the size of the flnal fluorescence level reached after addition of Mi+. It should be noted that in heat treated chloroplasts higher cation concentration is required to reach the maximal fluorescence level than in non-heated chloroplasts. Kinetic analysis of the salt induced increase of chlorophyll fluorescence indicated that the rate of increase of the distance between PSll and PSI complexes is markedly reduced in heat treated chloroplasts than in control. The salt induced time -dependent fluorescence changes are discussed in terms of heat -caused effects on the intra-thylakoid organization and physical properties of thylakoid membranes and their possible influence on the diffusion controlled lateral movement of chlorophyll-protein complexes of PSI and PSll.
International Journal of Molecular Sciences
Under natural environments, light quality and quantity are extremely varied. To respond and acclimate to such changes, plants have developed a multiplicity of molecular regulatory mechanisms. Non-photochemical quenching of chlorophyll fluorescence (NPQ) and thylakoid protein phosphorylation are two mechanisms that protect vascular plants. To clarify the role of thylakoid protein phosphorylation in energy-dependent quenching of chlorophyll fluorescence (qE) in rice plants, we used a direct Western blot assay after BN-PAGE to detect all phosphoproteins by P-Thr antibody as well as by P-Lhcb1 and P-Lhcb2 antibodies. Isolated thylakoids in either the dark- or the light-adapted state from wild type (WT) and PsbS-KO rice plants were used for this approach to detect light-dependent interactions between PsbS, PSII, and LHCII proteins. We observed that the bands corresponding to the phosphorylated Lhcb1 and Lhcb2 as well as the other phosphorylated proteins were enhanced in the PsbS-KO mutan...
Light-induced fluorescence quenching in the light-harvesting chlorophyll a/b protein complex
Photosynthesis Research, 1991
Irradiation of the principal photosystem II light-harvesting chlorophyll-protein antenna complex, LHC II, with high light intensities brings about a pronounced quenching of the chlorophyll fluorescence. Illumination of isolated thylakoids with high light intensities generates the formation of quenching centres within LHC II in vivo, as demonstrated by fluorescence excitation spectroscopy. In the isolated complex it is demonstrated that the light-induced fluorescence quenching: a) shows a partial, biphasic reversibility in the dark; b) is approximately proportional to the light intensity; c) is almost independent of temperature in the range 0-30°C; d) is substantially insensitive to protein modifying reagents and treatments; e) occurs in the absence of oxygen. A possible physiological importance of the phenomenon is discussed in terms of a mechanism capable of dissipating excess excitation energy within the photosystem II antenna. Abbreviations: chla-chlorophyll a; chlb-chlorophyll b; F 0-fluorescence yield with reaction centers open; F m-fluorescence yield with reaction centres closed; F i-fluorescence at the plateau level of the fast induction phase; LHC II-light-harvesting chlorophyll a/b protein complex II; PS II-photosystem II; PS I-photosystem I; Tricine-N-[2-hydroxy-l,l-bis(hydroxymethyl)ethyl]glycine
Photosynthesis research, 2000
Light induces conformational changes in the CP43 chl-a-protein antenna complex in isolated PS II core-complexes exposing phosphorylation site(s) to PS II core-associated protein kinase(s), to added solubilized thylakoid protein kinase(s), as well as to tryptic cleavage. The substrate-activation effect is demonstrated by exposure of the PS II cores to light during the kinase assay as well as by preillumination of the PS II cores in which the endogenous kinase(s) has been inactivated by treatment with N-ethylmaleimid. In the latter case, phosphorylation was performed in darkness following addition of the solubilized protein kinase(s). The solubilized protein kinase(s) does not require light activation. The apparent molecular masses of the main protein kinase(s) associated with the PS II cores (about 31-35 kDa and 45 kDa) differ from that of the major protein kinase present in solubilized preparations obtained from spinach thylakoids (64 kDa). The light-induced exposure of CP43 increas...