scholarly journals Balancing the two photosystems: photosynthetic electron transfer governs transcription of reaction centre genes in chloroplasts

2000 ◽  
Vol 355 (1402) ◽  
pp. 1351-1359 ◽  
Author(s):  
John F. Allen ◽  
Thomas Pfannschmidt
Keyword(s):  
Electron Transport ◽  
Genetic System ◽  
Regulatory Function ◽  
State Transitions ◽  
Transcriptional Level ◽  
Reaction Centre ◽  
Ps Ii ◽  
Ps I

Chloroplasts are cytoplasmic organelles whose primary function is photosynthesis, but which also contain small, specialized and quasi–autonomous genetic systems. In photosynthesis, two energy converting photosystems are connected, electrochemically, in series. The connecting electron carriers are oxidized by photosystem I (PS I) and reduced by photosystem II (PS II). It has recently been shown that the oxidation–reduction state of one connecting electron carrier, plastoquinone, controls transcription of chloroplast genes for reaction centre proteins of the two photosystems. The control counteracts the imbalance in electron transport that causes it: oxidized plastoquinone induces PS II and represses PS I; reduced plastoquinone induces PS I and represses PS II. This complementarity is observed both in vivo , using light favouring one or other photosystem, and in vitro , when site–specific electron transport inhibitors are added to transcriptionally and photosynthetically active chloroplasts. There is thus a transcriptional level of control that has a regulatory function similar to that of purely post–translational ‘state transitions’ in which the redistribution of absorbed excitation energy between photosystems is mediated by thylakoid membrane protein phosphorylation. The changes in rates of transcription that are induced by spectral changes in vivo can be detected even before the corresponding state transitions are complete, suggesting the operation of a branched pathway of redox signal transduction. These findings suggest a mechanism for adjustment of photosystem stoichiometry in which initial events involve a sensor of the redox state of plastoquinone, and may thus be the same as the initial events of state transitions. Redox control of chloroplast transcription is also consistent with the proposal that a direct regulatory coupling between electron transport and gene expression determines the function and composition of the chloroplast's extra–nuclear genetic system.

Photoinactivation of Photosynthetic Electron Transport under Anaerobic and Aerobic Conditions in Isolated Thylakoids of Spinach

1992 ◽  
Vol 47 (1-2) ◽  
pp. 63-68 ◽  
Author(s):  
Rekha Chaturvedi ◽  
M. Singh ◽  
P. V. Sane
Keyword(s):  
Electron Transport ◽  
Photosynthetic Electron Transport ◽  
Oxygen Evolving Complex ◽  
Reaction Centre ◽  
Ps Ii ◽  
Ps I ◽  
S2 State ◽  
The Stability ◽  
Oxygen Evolving ◽  
Spinach Thylakoids

Abstract The effect of exposure to strong white light on photosynthetic electron transport reactions of PS I and PS II were investigated in spinach thylakoids in the absence or presence of oxygen. Irrespective of the conditions used for photoinactivation, the damage to PS II was always much more than to PS I. Photoinactivation was severe under anaerobic conditions compared to that in air for the same duration. This shows that the presence of oxygen is required for prevention of photoinactivation of thylakoids. The susceptibility of water-splitting complex in photoinactivation is indicated by our data from experiments with chloride-deficient chloroplast membranes wherein it was observed that the whole chain electron transport from DPC to MV was much less photoinhibited than that from water. The data from the photoinactivation experiments with the Tris-treated thylakoids indicate another photodam age site at or near reaction centre of PS II. DCMU-protected PS II and oxygen-evolving complex from photoinactivation. DCMU protection can also be interpreted in terms of the stability of the PS II complex when it is in S2 state.

Isolierung von PS II-Partikeln mit in vivo Eigenschaften aus Euglena gracilis, Stamm Z / Isolation of PS II-Particels with in vivo Characteristics from Euglena gracilis, Stamm Z

1982 ◽  
Vol 37 (3-4) ◽  
pp. 256-259 ◽  
Author(s):  
F. Schuler ◽  
P. Brandt ◽  
W. Wießner
Keyword(s):  
Euglena Gracilis ◽  
Fluorescence Emission ◽  
Improved Method ◽  
Ps Ii ◽  
Ps I ◽  
Emission And Absorption Spectra ◽  
Chlorophyll Protein ◽  
Ps Ii Activity ◽  
Photosystem Ii Particles

Abstract An improved method for isolation of (photosystem II)-particles from Euglena gracilis, strain Z was established. PS II-particles isolated by ultrasonic treatment and following differential centrifugation show fluorescence emission and absorption spectra identical with in vivo properties of Euglena gracilis. These PS II-particles have only PS II-activity and contain CP a, the typical chlorophyll-protein-complex of PS II. No contamination of PS I-components are detectable.

scholarly journals Aberrantly high activation of a FoxM1–STMN1 axis contributes to progression and tumorigenesis in FoxM1-driven cancers

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Jun Liu ◽  
Jipeng Li ◽  
Ke Wang ◽  
Haiming Liu ◽  
Jianyong Sun ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Poor Prognosis ◽  
Soft Agar ◽  
Transcriptional Level ◽  
Regulation Mechanism ◽  
Strong Positive Correlation ◽  
Cell Viability Assay ◽  
High Level

AbstractFork-head box protein M1 (FoxM1) is a transcriptional factor which plays critical roles in cancer development and progression. However, the general regulatory mechanism of FoxM1 is still limited. STMN1 is a microtubule-binding protein which can inhibit the assembly of microtubule dimer or promote depolymerization of microtubules. It was reported as a major responsive factor of paclitaxel resistance for clinical chemotherapy of tumor patients. But the function of abnormally high level of STMN1 and its regulation mechanism in cancer cells remain unclear. In this study, we used public database and tissue microarrays to analyze the expression pattern of FoxM1 and STMN1 and found a strong positive correlation between FoxM1 and STMN1 in multiple types of cancer. Lentivirus-mediated FoxM1/STMN1-knockdown cell lines were established to study the function of FoxM1/STMN1 by performing cell viability assay, plate clone formation assay, soft agar assay in vitro and xenograft mouse model in vivo. Our results showed that FoxM1 promotes cell proliferation by upregulating STMN1. Further ChIP assay showed that FoxM1 upregulates STMN1 in a transcriptional level. Prognostic analysis showed that a high level of FoxM1 and STMN1 is related to poor prognosis in solid tumors. Moreover, a high co-expression of FoxM1 and STMN1 has a more significant correlation with poor prognosis. Our findings suggest that a general FoxM1-STMN1 axis contributes to cell proliferation and tumorigenesis in hepatocellular carcinoma, gastric cancer and colorectal cancer. The combination of FoxM1 and STMN1 can be a more precise biomarker for prognostic prediction.

scholarly journals Plant Physiology, 2021 Functional redox links between lumen thiol oxidoreductase1 and serine/threonine-protein kinase STN7

2021 ◽  
Author(s):  
Jianghao Wu ◽  
Liwei Rong ◽  
Weijun Lin ◽  
Lingxi Kong ◽  
Dengjie Wei ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Disulfide Bonds ◽  
Kinase Activity ◽  
Light Harvesting ◽  
Photosynthetic Electron Transport ◽  
State Transitions ◽  
Light Harvesting Complex ◽  
Light Harvesting Complex Ii

Abstract In response to changing light quantity and quality, photosynthetic organisms perform state transitions, a process which optimizes photosynthetic yield and mitigates photo-damage. The serine/threonine-protein kinase STN7 phosphorylates the light-harvesting complex of photosystem II (PSII; light-harvesting complex II), which then migrates from PSII to photosystem I (PSI), thereby rebalancing the light excitation energy between the photosystems and restoring the redox poise of the photosynthetic electron transport chain. Two conserved cysteines forming intra- or intermolecular disulfide bonds in the lumenal domain (LD) of STN7 are essential for the kinase activity although it is still unknown how activation of the kinase is regulated. In this study, we show lumen thiol oxidoreductase 1 (LTO1) is co-expressed with STN7 in Arabidopsis (Arabidopsis thaliana) and interacts with the LD of STN7 in vitro and in vivo. LTO1 contains thioredoxin (TRX)-like and vitamin K epoxide reductase domains which are related to the disulfide-bond formation system in bacteria. We further show that the TRX-like domain of LTO1 is able to oxidize the conserved lumenal cysteines of STN7 in vitro. In addition, loss of LTO1 affects the kinase activity of STN7 in Arabidopsis. Based on these results, we propose that LTO1 helps to maintain STN7 in an oxidized active state in state 2 through redox interactions between the lumenal cysteines of STN7 and LTO1.

scholarly journals Phosphorylation of Serine 303 Is a Prerequisite for the Stress-Inducible SUMO Modification of Heat Shock Factor 1

2003 ◽  
Vol 23 (8) ◽  
pp. 2953-2968 ◽  
Author(s):  
Ville Hietakangas ◽  
Johanna K. Ahlskog ◽  
Annika M. Jakobsson ◽  
Maria Hellesuo ◽  
Niko M. Sahlberg ◽  
...  
Keyword(s):  
Heat Shock ◽  
Phosphorylation Site ◽  
Stress Granules ◽  
Heat Shock Factor ◽  
Transcriptional Level ◽  
Heat Shock Factor 1 ◽  
Protection Mechanism ◽  
Sumo Modification

ABSTRACT The heat shock response, which is accompanied by a rapid and robust upregulation of heat shock proteins (Hsps), is a highly conserved protection mechanism against protein-damaging stress. Hsp induction is mainly regulated at transcriptional level by stress-inducible heat shock factor 1 (HSF1). Upon activation, HSF1 trimerizes, binds to DNA, concentrates in the nuclear stress granules, and undergoes a marked multisite phosphorylation, which correlates with its transcriptional activity. In this study, we show that HSF1 is modified by SUMO-1 and SUMO-2 in a stress-inducible manner. Sumoylation is rapidly and transiently enhanced on lysine 298, located in the regulatory domain of HSF1, adjacent to several critical phosphorylation sites. Sumoylation analyses of HSF1 phosphorylation site mutants reveal that specifically the phosphorylation-deficient S303 mutant remains devoid of SUMO modification in vivo and the mutant mimicking phosphorylation of S303 promotes HSF1 sumoylation in vitro, indicating that S303 phosphorylation is required for K298 sumoylation. This finding is further supported by phosphopeptide mapping and analysis with S303/7 phosphospecific antibodies, which demonstrate that serine 303 is a target for strong heat-inducible phosphorylation, corresponding to the inducible HSF1 sumoylation. A transient phosphorylation-dependent colocalization of HSF1 and SUMO-1 in nuclear stress granules provides evidence for a strictly regulated subnuclear interplay between HSF1 and SUMO.

scholarly journals Direct repeats bind the EcR/USP receptor and mediate ecdysteroid responses in Drosophila melanogaster.

1996 ◽  
Vol 16 (6) ◽  
pp. 2977-2986 ◽  
Author(s):  
C Antoniewski ◽  
B Mugat ◽  
F Delbac ◽  
J A Lepesant
Keyword(s):  
Fat Body ◽  
Cell Transformation ◽  
Direct Repeat ◽  
Transgenic Animals ◽  
Transcriptional Level ◽  
Regulatory Sequences ◽  
Direct Repeats ◽  
Fbp1 Gene

The steroid hormone 20-hydroxyecdysone plays a key role in the induction and modulation of morphogenetic events throughout Drosophila development. Previous studies have shown that a heterodimeric nuclear receptor composed of the EcR and USP proteins mediates the action of the hormone at the transcriptional through binding to palindromic ecdysteroid mediates the action of the hormone at the transcriptional level through binding to palindromic ecdysteroid response elements (EcREs) such as those present in the promoter of the hsp27 gene or the fat body-specific enhancer of the Fbp1 gene. We show that in addition to palindromic EcREs, the EcR/USP heterodimer can bind in vitro with various affinities to direct repetitions of the motif AGGTCA separated by 1 to 5 nucleotides (DR1 to DR5), which are known to be target sites for vertebrate nuclear receptors. At variance with the receptors, EcR/USP was also found to bind to a DR0 direct repeat with no intervening nucleotide. In cell transformation assays, direct repeats DR0 to DR5 alone can render the minimum viral tk or Drosophila Fbp1 promoter responsive to 20-hydroxyecdysone, as does the palindromic hsp27 EcRE. In a transgenic assay, however, neither the palindromic hsp27 element nor direct repeat DR3 alone can make the Fbp1 minimal promoter responsive to premetamorphic ecdysteroid peaks. In contrast, DR0 and DR3 elements, when substituted for the natural palindromic EcRE in the context of the Fbp1 enhancer, can drive a strong fat body-specific ecdysteroid response in transgenic animals. These results demonstrate that directly repeated EcR/USP binding sites are as effective as palindromic EcREs in vivo. They also provide evidence that additional flanking regulatory sequences are crucially required to potentiate the hormonal response mediated by both types of elements and specify its spatial and temporal pattern.

scholarly journals Membrane Stored Curvature Elastic Stress Modulates Recruitment of Maintenance Proteins PspA and Vipp1

mBio ◽  
2015 ◽  
Vol 6 (5) ◽  
Author(s):  
Christopher McDonald ◽  
Goran Jovanovic ◽  
Oscar Ces ◽  
Martin Buck
Keyword(s):  
Elastic Stress ◽  
Membrane Binding ◽  
Membrane Integrity ◽  
Regulatory Function ◽  
Membrane Stress ◽  
Inner Membrane ◽  
Thylakoid Biogenesis ◽  
Stress Dependent

ABSTRACTPhage shock protein A (PspA), which is responsible for maintaining inner membrane integrity under stress in enterobacteria, and vesicle-inducting protein in plastids 1 (Vipp1), which functions for membrane maintenance and thylakoid biogenesis in cyanobacteria and plants, are similar peripheral membrane-binding proteins. Their homologous N-terminal amphipathic helices are required for membrane binding; however, the membrane features recognized and required for expressing their functionalities have remained largely uncharacterized. Rigorously controlled,in vitromethodologies with lipid vesicles and purified proteins were used in this study and provided the first biochemical and biophysical characterizations of membrane binding by PspA and Vipp1. Both proteins are found to sense stored curvature elastic (SCE) stress and anionic lipids within the membrane. PspA has an enhanced sensitivity for SCE stress and a higher affinity for the membrane than Vipp1. These variations in binding may be crucial for some of the proteins’ differing rolesin vivo. Assays probing the transcriptional regulatory function of PspA in the presence of vesicles showed that a relief of transcription inhibition occurs in an SCE stress-specific manner. Thisin vitrorecapitulation of membrane stress-dependent transcription control suggests that the Psp response may be mountedin vivowhen a cell's inner membrane experiences increased SCE stress.IMPORTANCEAll cell types maintain the integrity of their membrane systems. One widely distributed membrane stress response system in bacteria is the phage shock protein (Psp) system. The central component, peripheral membrane protein PspA, which mitigates inner membrane stress in bacteria, has a counterpart, Vipp1, which functions for membrane maintenance and thylakoid biogenesis in plants and photosynthetic bacteria. Membrane association of both these proteins is accepted as playing a pivotal role in their functions. Here we show that direct membrane binding by PspA and Vipp1 is driven by two physio-chemical signals, one of which is membrane stress specific. Our work points to alleviation of membrane stored curvature elastic stress by amphipathic helix insertions as an attractive mechanism for membrane maintenance by PspA and Vipp1. Furthermore, the identification of a physical, stress-related membrane signal suggests a unilateral mechanism that promotes both binding of PspA and induction of the Psp response.

scholarly journals The Ubiquitously Expressed Csk Adaptor Protein Cbp Is Dispensable for Embryogenesis and T-Cell Development and Function

2005 ◽  
Vol 25 (23) ◽  
pp. 10533-10542 ◽  
Author(s):  
Marc-Werner Dobenecker ◽  
Christian Schmedt ◽  
Masato Okada ◽  
Alexander Tarakhovsky
Keyword(s):  
T Cell ◽  
Adaptor Protein ◽  
Regulatory Function ◽  
Loss Of Function ◽  
Thymic Development ◽  
Cell Functions ◽  
Carboxy Terminal ◽  
And Function

ABSTRACT Regulation of Src family kinase (SFK) activity is indispensable for a functional immune system and embryogenesis. The activity of SFKs is inhibited by the presence of the carboxy-terminal Src kinase (Csk) at the cell membrane. Thus, recruitment of cytosolic Csk to the membrane-associated SFKs is crucial for its regulatory function. Previous studies utilizing in vitro and transgenic models suggested that the Csk-binding protein (Cbp), also known as phosphoprotein associated with glycosphingolipid microdomains (PAG), is the membrane adaptor for Csk. However, loss-of-function genetic evidence to support this notion was lacking. Herein, we demonstrate that the targeted disruption of the cbp gene in mice has no effect on embryogenesis, thymic development, or T-cell functions in vivo. Moreover, recruitment of Csk to the specialized membrane compartment of “lipid rafts” is not impaired by Cbp deficiency. Our results indicate that Cbp is dispensable for the recruitment of Csk to the membrane and that another Csk adaptor, yet to be discovered, compensates for the loss of Cbp.

scholarly journals RanBP2 and SENP3 Function in a Mitotic SUMO2/3 Conjugation-Deconjugation Cycle on Borealin

2009 ◽  
Vol 20 (1) ◽  
pp. 410-418 ◽  
Author(s):  
Ulf R. Klein ◽  
Markus Haindl ◽  
Erich A. Nigg ◽  
Stefan Muller
Keyword(s):  
Mammalian Cells ◽  
Spindle Assembly Checkpoint ◽  
Critical Role ◽  
Specific Interaction ◽  
Regulatory Function ◽  
Mitotic Progression ◽  
Chromosome Congression ◽  
Chromosomal Passenger

The ubiquitin-like SUMO system controls cellular key functions, and several lines of evidence point to a critical role of SUMO for mitotic progression. However, in mammalian cells mitotic substrates of sumoylation and the regulatory components involved are not well defined. Here, we identify Borealin, a component of the chromosomal passenger complex (CPC), as a mitotic target of SUMO. The CPC, which additionally comprises INCENP, Survivin, and Aurora B, regulates key mitotic events, including chromosome congression, the spindle assembly checkpoint, and cytokinesis. We show that Borealin is preferentially modified by SUMO2/3 and demonstrate that the modification is dynamically regulated during mitotic progression, peaking in early mitosis. Intriguingly, the SUMO ligase RanBP2 interacts with the CPC, stimulates SUMO modification of Borealin in vitro, and is required for its modification in vivo. Moreover, the SUMO isopeptidase SENP3 is a specific interaction partner of Borealin and catalyzes the removal of SUMO2/3 from Borealin. These data thus delineate a mitotic SUMO2/3 conjugation–deconjugation cycle of Borealin and further assign a regulatory function of RanBP2 and SENP3 in the mitotic SUMO pathway.

The Drosophila extramacrochaetae protein antagonizes sequence-specific DNA binding by daughterless/achaete-scute protein complexes

Development ◽  
1991 ◽  
Vol 113 (1) ◽  
pp. 245-255 ◽  
Author(s):  
M. Van Doren ◽  
H.M. Ellis ◽  
J.W. Posakony
Keyword(s):  
Dna Binding ◽  
Cell Fate ◽  
Protein Complexes ◽  
Competitive Inhibitor ◽  
Binding Activity ◽  
Regulatory Function ◽  
Biochemical Basis ◽  
Dna Binding Activity

In Drosophila, a group of regulatory proteins of the helix-loop-helix (HLH) class play an essential role in conferring upon cells in the developing adult epidermis the competence to give rise to sensory organs. Proteins encoded by the daughterless (da) gene and three genes of the achaete-scute complex (AS-C) act positively in the determination of the sensory organ precursor cell fate, while the extramacrochaetae (emc) and hairy (h) gene products act as negative regulators. In the region upstream of the achaete gene of the AS-C, we have identified three ‘E box’ consensus sequences that are bound specifically in vitro by hetero-oligomeric complexes consisting of the da protein and an AS-C protein. We have used this DNA-binding activity to investigate the biochemical basis of the negative regulatory function of emc. Under the conditions of our experiments, the emc protein, but not the h protein, is able to antagonize specifically the in vitro DNA-binding activity of da/AS-C and putative da/da protein complexes. We interpret these results as follows: the heterodimerization capacity of the emc protein (conferred by its HLH domain) allows it to act in vivo as a competitive inhibitor of the formation of functional DNA-binding protein complexes by the da and AS-C proteins, thereby reducing the effective level of their transcriptional regulatory activity within the cell.

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