排序方式: 共有26条查询结果,搜索用时 15 毫秒
1.
Ute Armbruster Mathias Labs Mathias Pribil Stefania Viola Wenteng Xu Michael Scharfenberg Alexander P. Hertle Ulrike Rojahn Poul Erik Jensen Fabrice Rappaport Pierre Joliot Peter D?rmann Gerhard Wanner Dario Leister 《The Plant cell》2013,25(7):2661-2678
Chloroplasts of land plants characteristically contain grana, cylindrical stacks of thylakoid membranes. A granum consists of a core of appressed membranes, two stroma-exposed end membranes, and margins, which connect pairs of grana membranes at their lumenal sides. Multiple forces contribute to grana stacking, but it is not known how the extreme curvature at margins is generated and maintained. We report the identification of the CURVATURE THYLAKOID1 (CURT1) protein family, conserved in plants and cyanobacteria. The four Arabidopsis thaliana CURT1 proteins (CURT1A, B, C, and D) oligomerize and are highly enriched at grana margins. Grana architecture is correlated with the CURT1 protein level, ranging from flat lobe-like thylakoids with considerably fewer grana margins in plants without CURT1 proteins to an increased number of membrane layers (and margins) in grana at the expense of grana diameter in overexpressors of CURT1A. The endogenous CURT1 protein in the cyanobacterium Synechocystis sp PCC6803 can be partially replaced by its Arabidopsis counterpart, indicating that the function of CURT1 proteins is evolutionary conserved. In vitro, Arabidopsis CURT1A proteins oligomerize and induce tubulation of liposomes, implying that CURT1 proteins suffice to induce membrane curvature. We therefore propose that CURT1 proteins modify thylakoid architecture by inducing membrane curvature at grana margins. 相似文献
2.
Hald S Pribil M Leister D Gallois P Johnson GN 《Biochimica et biophysica acta》2008,1777(9):1173-1183
Photosynthetic electron transport can involve either a linear flow from water to NADP, via Photosystems (PS) II and I or a cyclic flow just involving PSI. Little is known about factors regulating the relative flow through each of these pathways. We have examined photosynthetic electron transport through each system in plants of Arabidopsis thaliana in which either the PSI-D1 or PSI-E1 subunits of PSI have been knocked out. In both cases, this results in an imbalance in the turnover of PSI and PSII, such that PSII electron transport is limited by PSI turnover. Phosphorylation of light-harvesting complex II (LHCII) and its migration to PSI is enhanced but only partially reversible and not sufficient to balance photosystem turnover. In spite of this, cyclic electron flow is able to compete efficiently with PSI across a range of conditions. In dark-adapted leaves, the efficiency of cyclic relative to linear flow induced by far-red light is increased, implying that the limiting step of cyclic flow lies in the re-injection of electrons into the electron transport chain. Illumination of leaves with white light resulted in transient induction of a significant non-photochemical quenching in knockout plants which is probably high energy state quenching induced by cyclic electron flow. At high light and at low CO(2), non-photochemical quenching was greater in the knockout plants than in the wildtype. Comparison of PSI and PSII turnover under such conditions suggested that this is generated by cyclic electron flow around PSI. We conclude that, when the concentration of PSI is limiting, cyclic electron flow is still able to compete effectively with linear flow to maintain a high DeltapH to regulate photosynthesis. 相似文献
3.
Brood parasites lay unusually strong eggs, presumably to prevent puncture ejection of the eggs by hosts. However, it has been suggested that eggs of some parasitic cuckoos have normal strength. This suggestion was based on the eggshell thickness and shape of these eggs. Here, we propose that there may be other structural adaptations (such as increased eggshell density) that make the cuckoo eggs unusually strong. In this study, we compared the eggshell density of parasitic cuckoos to the eggshell density of two control groups, non-parasitic cuckoos and a sample of non-passerine species. The comparisons to both control groups demonstrated that the parasitic cuckoos have eggshells of significantly higher density than would be expected for their size. Our results support the hypothesis that the higher eggshell density is an alternative mechanism by which some cuckoos increase the strength of their eggs. 相似文献
4.
Mathias Pribil Paolo Pesaresi Alexander Hertle Roberto Barbato Dario Leister 《PLoS biology》2010,8(1)
Short-term changes in illumination elicit alterations in thylakoid protein phosphorylation and reorganization of the photosynthetic machinery. Phosphorylation of LHCII, the light-harvesting complex of photosystem II, facilitates its relocation to photosystem I and permits excitation energy redistribution between the photosystems (state transitions). The protein kinase STN7 is required for LHCII phosphorylation and state transitions in the flowering plant Arabidopsis thaliana. LHCII phosphorylation is reversible, but extensive efforts to identify the protein phosphatase(s) that dephosphorylate LHCII have been unsuccessful. Here, we show that the thylakoid-associated phosphatase TAP38 is required for LHCII dephosphorylation and for the transition from state 2 to state 1 in A. thaliana. In tap38 mutants, thylakoid electron flow is enhanced, resulting in more rapid growth under constant low-light regimes. TAP38 gene overexpression markedly decreases LHCII phosphorylation and inhibits state 1→2 transition, thus mimicking the stn7 phenotype. Furthermore, the recombinant TAP38 protein is able, in an in vitro assay, to directly dephosphorylate LHCII. The dependence of LHCII dephosphorylation upon TAP38 dosage, together with the in vitro TAP38-mediated dephosphorylation of LHCII, suggests that TAP38 directly acts on LHCII. Although reversible phosphorylation of LHCII and state transitions are crucial for plant fitness under natural light conditions, LHCII hyperphosphorylation associated with an arrest of photosynthesis in state 2 due to inactivation of TAP38 improves photosynthetic performance and plant growth under state 2-favoring light conditions. 相似文献
5.
Tn 10/IS 10 transposition involves excision of the transposon from a donor site and subsequent joining of the excised transposon to a new target site. These steps are catalyzed by the Tn 10 -encoded transposase protein and require the presence of a suitable divalent metal ion. Like other transposase and retroviral integrase proteins, Tn 10 transposase appears to contain a single active site which includes a triad of acidic amino acid residues generally referred to as the DDE motif. In addition to its role in catalysis, the Tn 10 transposase DDE motif also functions in target capture, a step that in vitro is greatly facilitated by the presence of a suitable divalent metal ion. We show that cysteine residue substitutions at each of the DDE motif residues in Tn 10 transposase result in a change in the divalent metal ion requirements for catalysis, such that Mn2+but not Mg2+can be used. This switch in metal ion specificity provides evidence that each of the DDE motif residues functions directly in metal ion binding. We also show differential effects of DDE mutations on metal ion-assisted target capture. A number of models, including a two metal ion active site, are considered to explain these effects. 相似文献
6.
Fabio Facchinelli Mathias Pribil Ulrike Oster Nina J. Ebert Debashish Bhattacharya Dario Leister Andreas P. M. Weber 《Planta》2013,237(2):637-651
Glaucophytes represent the first lineage of photosynthetic eukaryotes of primary endosymbiotic origin that diverged after plastid establishment. The muroplast of Cyanophora paradoxa represents a primitive plastid that resembles its cyanobacterial ancestor in pigment composition and the presence of a peptidoglycan wall. To attain insights into the evolutionary history of cyanobiont integration and plastid development, it would thus be highly desirable to obtain knowledge on the composition of the glaucophyte plastid proteome. Here, we provide the first proteomic analysis of the muroplast of C. paradoxa. Mass spectrometric analysis of the muroplast proteome identified 510 proteins with high confidence. The protein repertoire of the muroplast revealed novel paths for reduced carbon flow and export to the cytosol through a sugar phosphate transporter of chlamydial origin. We propose that C. paradoxa possesses a primordial plastid mirroring the situation in the early protoalga. 相似文献
7.
Humayun S Wardle SJ Shilton BH Pribil PA Liburd J Haniford DB 《Journal of molecular biology》2005,346(3):703-716
Transposition reactions take place in the context of higher-order protein-DNA complexes called transpososomes. In the Tn10 transpososome, IHF binding to an "outside end" creates a bend in the DNA that allows the transposase protein to contact the end at two different sites, the terminal and subterminal binding sites. Presumably this helps to stabilize the transposase-end interaction. However, the DNA loop that is formed must be unfolded at a later stage in order for the transposon to integrate into other DNA molecules. It has been proposed that transpososome unfolding also plays a role in transposon excision. To investigate this possibility further, we have isolated and characterized transposase mutants with altered transpososome unfolding properties. Two such mutants were identified, R182A and R184A. Both mutants fail to carry out hairpin formation, an intermediate step in transposon excision, specifically with outside end-containing substrates. These results support the idea that transpososome unfolding and excision are linked. Also, based on the importance of residues R182 and R184 in transpososome unfolding, we propose a new model for the Tn10 transpososome, wherein both DNA ends of the transpososome make subterminal contacts with transposase. 相似文献
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9.
Adrienne L. Jones Jordan Clayborn Elizabeth Pribil Andrew P. Foote Dagan Montogomery Mostafa S. Elshahed Noha H. Youssef 《Environmental microbiology》2023,25(11):2088-2101
Establishment of microbial communities in neonatal calves is vital for their growth and overall health. While this process has received considerable attention for bacteria, our knowledge on temporal progression of anaerobic gut fungi (AGF) in calves is lacking. Here, we examined AGF communities in faecal samples from six dairy cattle collected at 24 different time points during the pre-weaning (days 1–48), weaning (days 48–60), and post-weaning (days 60–360) phases. Quantitative polymerase chain reaction indicated that AGF colonisation occurs within 24 h after birth, with loads slowly increasing during pre-weaning and weaning, then drastically increasing post-weaning. Culture-independent amplicon surveys identified higher alpha diversity during pre-weaning/weaning, compared to post-weaning. AGF community structure underwent a drastic shift post-weaning, from a community enriched in genera commonly encountered in hindgut fermenters to one enriched in genera commonly encountered in adult ruminants. Comparison of AGF community between calves day 1 post-birth and their mothers suggest a major role for maternal transmission, with additional input from cohabitating subjects. This distinct pattern of AGF progression could best be understood in-light of their narrower niche preferences, metabolic specialisation, and physiological optima compared to bacteria, hence eliciting a unique response to changes in feeding pattern and associated structural GIT development during maturation. 相似文献
10.
Calicivirus Inactivation by Nonionizing (253.7-Nanometer-Wavelength [UV]) and Ionizing (Gamma) Radiation 总被引:5,自引:3,他引:2
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Ana Maria de Roda Husman Paul Bijkerk Willemijn Lodder Harold van den Berg Walter Pribil Alexander Cabaj Peter Gehringer Regina Sommer Erwin Duizer 《Applied microbiology》2004,70(9):5089-5093
Noroviruses (previously Norwalk-like viruses) are the most common viral agents associated with food- and waterborne outbreaks of gastroenteritis. In the absence of culture methods for noroviruses, animal caliciviruses were used as model viruses to study inactivation by nonionizing (253.7-nm-wavelength [UV]) and ionizing (gamma) radiation. Here, we studied the respiratory feline calicivirus (FeCV) and the presumed enteric canine calicivirus (CaCV) and compared them with the well-studied bacteriophage MS2. When UV irradiation was used, a 3-log10 reduction was observed at a fluence of 120 J/m2 in the FeCV suspension and at a fluence of 200 J/m2 for CaCV; for the more resistant phage MS2 there was a 3-log10 reduction at a fluence of 650 J/m2. Few or no differences were observed between levels of UV inactivation in high- and low-protein-content virus stocks. In contrast, ionizing radiation could readily inactivate MS2 in water, and there was a 3-log10 reduction at a dose of 100 Gy, although this did not occur when the phage was diluted in high-protein-content stocks of CaCV or FeCV. The low-protein-content stocks showed 3-log10 reductions at a dose of 500 Gy for FeCV and at a dose of 300 for CaCV. The inactivation rates for both caliciviruses with ionizing and nonionizing radiation were comparable but different from the inactivation rates for MS2. Although most FeCV and CaCV characteristics, such as overall particle and genome size and structure, are similar, the capsid sequences differ significantly, making it difficult to predict human norovirus inactivation. Adequate management of UV and gamma radiation processes for virus inactivation should limit public health risks. 相似文献