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201.
Photoinhibition and xanthophyll cycle activity in bayberry (Myrica rubra) leaves induced by high irradiance 总被引:1,自引:0,他引:1
The effect of high irradiance (HI, photosynthetically active photon flux density of 1 300 μmol m−2 s−1) on net photosynthetic rate (P
N), chlorophyll fluorescence parameters, and xanthophyll cycle components were studied in fruit tree bayberry leaves. HI induced
the photoinhibition and inactivation of photosystem 2 (PS2) reaction centres (RCs), which was characterized by decreased P
N, maximum yield of fluorescence after dark adaptation (Fm), photochemical efficiency of PS2 (Fv/Fm) and quantum yield of PS2 (ΦPS2), and increased reduction state of QA (1-qP) and non-photochemical quenching (NPQ). Initial fluorescence (F0) showed a decrease after the first 2 h, and subsequently increased from the third hour exposure to HI. Furthermore, a greater
increase in the ratio (Fi-F0)/(Fp-F0) which is an expression of the proportion of the QB non-reducing PS2 centres, whereas a remarked decrease in the slope of Fi to Fp which represents the rate of QA reduction was observed in leaves after HI exposure. Additionally, HI caused an increase in the pool size of the xanthophyll
cycle pigments and sustained elevated contents of zeaxanthin (Z), antheraxanthin (A), and de-epoxidation state (DES) at the
end of the irradiation period. During HI, decreased Fm, Fv/Fm, ΦPS2, NPQ, slope of Fi to Fp, V+A+Z, and DES, and increased F0, 1-qP, ratio (Fi-F0)/(Fp-F0), and V were observed in dithiothreitol (DTT)-fed leaves compared to control ones under the same conditions. Hence photoinhibition
caused by HI in bayberry was probably attributed to inactivation of PS2 RCs, and photoprotection from photodamage were mainly
related to the xanthophyll cycle-dependent heat dissipation in excess photons. 相似文献
202.
Mariângela S.S. Diz André O. Carvalho Rosana Rodrigues Ana Gisele C. Neves-Ferreira Maura Da Cunha Elias Walter Alves Anna L. Okorokova-Façanha Marco Antônio Oliveira Jonas Perales Olga L.T. Machado Valdirene M. Gomes 《Biochimica et Biophysica Acta (BBA)/General Subjects》2006
During the last few years, a growing number of cysteine-rich antimicrobial peptides has been isolated from plants and particularly from seeds. It has become increasingly clear that these peptides play an important role in the protection of plants against microbial infection. In this work, proteins from chilli pepper (Capsicum annuum L.) seeds were extracted in phosphate buffer, pH 5.4 and peptides purification were performed by employing ion-exchange chromatographies on DEAE, CM-Sepharose, Sephacryl S-100 and reverse phase in HPLC. Three peptide enriched fractions, namely F1, F2 and F3, were obtained after the CM-Sepharose chromatography. The F1 fraction, mainly composed of three peptides ranging from 6 to 10 kDa, was submitted to N-terminal amino acid sequencing. The closer to 10 kDa peptide showed high sequence homology to lipid transfer proteins (LTPs) previously isolated from others seeds. F1 fraction exhibited strong fungicidal activity against Candida albicans, Saccharomyces cerevisiae and Schizosaccharomyces pombe and also promoted several morphological changes to C. albicans, including the formation of pseudohyphae, as revealed by scanning electron micrography. F1 fraction also reduced the glucose stimulated acidification of the medium mediated by H+-ATPase of S. cerevisiae cells in a dose-dependent manner and caused the permeabilization of yeast plasma membrane to the dye SYTOX Green, as verified by confocal laser microscopy. 相似文献
203.
Jochen Zimmer 《生物化学与生物物理学报:生物膜》2006,1758(5):645-652
Detergent solubilization and purification of the E. coli heavy metal P-type ATPase ZntA yields an enzyme with reduced hydrolytic activity in vitro. Here, it is shown that the in vitro hydrolytic activity of detergent solubilized ZntA is increased in the presence of negatively charged phospholipids and at slightly acidic pH. The protein-lipid interaction of ZntA was characterized by enzyme-coupled ATPase assays and fluorescence spectroscopy. Among the most abundant naturally occurring phospholipids, only phosphatidyl-glycerol lipids (PG) enhance the in vitro enzymatic ATPase activity of ZntA. Re-lipidation of detergent purified ZntA with 1,2-dioleoylphosphatidyl-glycerol (DOPG) increases the ATPase activity four-fold compared to the purified state. All other E. coli phospholipids fail to activate the ATPase. Among the phosphatidyl-glycerol family, highest activity was observed for 1,2-dioleoyl-PG followed by 1,2-dimyristoyl-PG, 1,2-dipalmitoyl-PG and 1,2-distearoyl-PG. Increasing intrinsic Trp fluorescence quantum yield upon relipidation of ZntA was used to determine a pH maximum for lipid binding at pH 6.7. The pH dependence of the lipid binding was confirmed by pH-dependent ATPase assays showing maximum activity at pH 6.7. The biophysical characterization of detergent solubilized membrane proteins crucially relies on the conformational stability and functional integrity of the protein under investigation. The present study describes how the E. coli ZntA P-type ATPase can be stabilized and functionally activated in a detergent solubilized system. 相似文献
204.
Kanzo Suzuki Fumitaka Kawakami Hisashi Sasaki Hiroko Maruyama Kenzo Ohtsuki 《Biochimica et Biophysica Acta (BBA)/General Subjects》2009
Background
We recently reported that both sulfatide and cholesterol-3-sulfate (SCS) function as potent stimulators for the GSK-3β-mediated phosphorylation of tau protein (TP) in vitro [J. Biochem. 143 (2008) 359–367].Methods
By means of successive gel filtration on a Superdex 200 pg column and three distinct ion-exchange column chromatographies, TP and its associated proteins were highly purified from the extract of rat brain.Results
We found that (i) syndapin 1 and novel protein kinase C? (nPKC?) were identified as the TP-associated proteins; (ii) SCS highly stimulated the phosphorylation of TP and syndapin 1 by nPKC? as well as CK1; (iii) the full phosphorylation of TP and syndapin 1 by nPKC? in the presence of sulfatide resulted in their dissociation; (iv) TP primed by CK1 functioned as an effective phosphate acceptor for GSK-3β; (v) syndapin 1 highly stimulated the GSK-3β-mediated phosphorylation of TP; and (vi) TP isoforms were highly expressed in aged brain, whereas syndapin 1 was consistently detected in adult brain, but not in newborn brain.General significance
These results provided here suggest that (i) TP-associated nPKC? suppresses the GSK-3β-mediated phosphorylation of TP through the phosphorylation of GSK-3β by the kinase in vitro; and (ii) SCS act as effective sole mediators to induce the GSK-3β-mediated high phosphorylation of both TP and its associated syndapin 1 involved in the biochemical processes of neuronal diseases, including Alzheimer's disease. 相似文献205.
Conformational changes of the Na+/K+-ATPase isolated large cytoplasmic segment connecting transmembrane helices M4 and M5 (C45) induced by the interaction with enzyme ligands (i.e. Mg2+ and/or ATP) were investigated by means of the intrinsic tryptophan fluorescence measurement and molecular dynamic simulations. Our data revealed that this model system consisting of only two domains retained the ability to adopt open or closed conformation, i.e. behavior, which is expected from the crystal structures of relative Ca2+-ATPase from sarco(endo)plasmic reticulum for the corresponding part of the entire enzyme. Our data revealed that the C45 is found in the closed conformation in the absence of any ligand, in the presence of Mg2+ only, or in the simultaneous presence of Mg2+ and ATP. Binding of the ATP alone (i.e. in the absence of Mg2+) induced open conformation of the C45. The fact that the transmembrane part of the enzyme was absent in our experiments suggested that the observed conformational changes are consequences only of the interaction with ATP or Mg2+ and may not be related to the transported cations binding/release, as generally believed. Our data are consistent with the model, where ATP binding to the low-affinity site induces conformational change of the cytoplasmic part of the enzyme, traditionally attributed to E2 → E1 transition, and subsequent Mg2+ binding to the enzyme-ATP complex induces in turn conformational change traditionally attributed to E1 → E2 transition. 相似文献
206.
Takeshi Hiromoto Oliver Pilak Marco Salomone Stagni Eberhard Warkentin Seigo Shima Ulrich Ermler 《FEBS letters》2009,583(3):585-771
[Fe]-hydrogenase is one of three types of enzymes known to activate H2. Crystal structure analysis recently revealed that its active site iron is ligated square-pyramidally by Cys176-sulfur, two CO, an “unknown” ligand and the sp2-hybridized nitrogen of a unique iron-guanylylpyridinol-cofactor. We report here on the structure of the C176A mutated enzyme crystallized in the presence of dithiothreitol (DTT). It suggests an iron center octahedrally coordinated by one DTT-sulfur and one DTT-oxygen, two CO, the 2-pyridinol’s nitrogen and the 2-pyridinol’s 6-formylmethyl group in an acyl-iron ligation. This result led to a re-interpretation of the iron ligation in the wild-type. 相似文献
207.
Dong Han 《FEBS letters》2009,583(12):1928-21656
Clustered regularly interspaced short palindromic repeats (CRISPR) and their associated protein genes (cas genes) are ubiquitous in archaea and eubacteria. It has been suggested that CRISPR and CAS proteins act as an immune system preventing the invasion of foreign genomic elements at the DNA level. The protein SSO1450 from Sulfolobus solfataricus (Sso) P2 belongs to the CAS1 cluster which is one of the core protein clusters most frequently associated with CRISPR sequences. In this study we show that SSO1450 is a high-affinity nucleic acid binding protein. It binds DNA, RNA and DNA-RNA hybrid apparently sequence non-specific in a multi-site binding mode. Furthermore, SSO1450 promotes the hybridization of complementary nucleic acid strands. 相似文献
208.
Valeria Petronilli Alessandra Zulian Giulio Jori Giuseppe Tognon Paolo Bernardi 《BBA》2009,1787(7):897-172
We have studied the mitochondrial permeability transition pore (PTP) under oxidizing conditions with mitochondria-bound hematoporphyrin, which generates reactive oxygen species (mainly singlet oxygen, 1O2) upon UV/visible light-irradiation and promotes the photooxidative modification of vicinal targets. We have characterized the PTP-modulating properties of two major critical sites endowed with different degrees of photosensitivity: (i) the most photovulnerable site comprises critical histidines, whose photomodification by vicinal hematoporphyrin causes a drop in reactivity of matrix-exposed (internal), PTP-regulating cysteines thus stabilizing the pore in a closed conformation; (ii) the most photoresistant site coincides with the binding domains of (external) cysteines sensitive to membrane-impermeant reagents, which are easily unmasked when oxidation of internal cysteines is prevented. Photooxidation of external cysteines promoted by vicinal hematoporphyrin reactivates the PTP after the block caused by histidine photodegradation. Thus, hematoporphyrin-mediated photooxidative stress can either inhibit or activate the mitochondrial permeability transition depending on the site of hematoporphyrin localization and on the nature of the substrate; and selective photomodification of different hematoporphyrin-containing pore domains can be achieved by fine regulation of the sensitizer/light doses. These findings shed new light on PTP modulation by oxidative stress. 相似文献
209.
Yoshikazu Fujii Hiroki Kabumoto Tadashi Fujii Koji Takeda Akira Arisawa Tomohiro Tamura 《Biochemical and biophysical research communications》2009,385(2):170-8310
Vitamin D3 (VD3) is a fat-soluble prohormone that plays a crucial role in bone metabolism, immunity, and control of cell proliferation and cell differentiation in mammals. The actinomycete Pseudonocardia autotrophica is capable of bioconversion of VD3 into its physiologically active forms, namely, 25(OH)VD3 or 1α,25(OH)2VD3. In this study, we isolated and characterized Vdh (vitamin D3 hydroxylase), which hydroxylates VD3 from P. autotrophica NBRC 12743. The vdh gene encodes a protein containing 403 amino acids with a molecular weight of 44,368 Da. This hydroxylase was found to be homologous with the P450 belonging to CYP107 family. Vdh had the same ratio of the Vmax values for VD3 25-hydroxylation and 25(OH)VD3 1α-hydroxylation, while other enzymes showed preferential regio-specific hydroxylation on VD3. We characterized a collection of Vdh mutants obtained by random mutagenesis and obtained a Vdh-K1 mutant by the combination of four amino acid substitutions. Vdh-K1 showed one-order higher VD3 25-hydroxylase activity than the wild-type enzyme. Biotransformation of VD3 into 25(OH)VD3 was successfully accomplished with a Vdh-expressed recombinant strain of actinobacterium Rhodococcus erythropolis. Vdh may be a useful enzyme for the production of physiologically active forms of VD3 by a single cytochrome P450. 相似文献
210.
Kumiko Sakai-Kato Yoshinori Umezawa Jun Aruga Naoko Utsunomiya-Tate 《Biochemical and biophysical research communications》2009,384(3):362-365
Zic family proteins have five C2H2-type zinc finger (ZF) motifs. We physicochemically characterized the folding properties of Zic ZFs. Alteration of chelation with zinc ions and of hydrophobic interactions changed circular dichroism spectra, suggesting that they caused structural changes. The motifs were heat stable, but electrostatic interactions had little effect on structural stability. These results highlight the importance of chelating interactions and hydrophobic interactions for the stability of the folding structure of Zic ZF proteins. 相似文献