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101.
102.
Sugiura M Ogami S Kusumi M Un S Rappaport F Boussac A 《The Journal of biological chemistry》2012,287(16):13336-13347
The main cofactors that determine the photosystem II (PSII) oxygen evolution
activity are borne by the D1 and D2 subunits. In the cyanobacterium
Thermosynechococcus elongatus, there are three
psbA genes coding for D1. Among the 344 residues
constituting D1, there are 21 substitutions between PsbA1 and PsbA3, 31 between
PsbA1 and PsbA2, and 27 between PsbA2 and PsbA3. Here, we present the first
study of PsbA2-PSII. Using EPR and UV-visible time-resolved absorption
spectroscopy, we show that: (i) the time-resolved EPR spectrum of TyrZ• in the
(S3TyrZ•)′ is slightly modified; (ii) the split EPR signal
arising from TyrZ• in the (S2TyrZ•)′ state induced by near-infrared
illumination at 4.2 K of the S3TyrZ state is significantly
modified; and (iii) the slow phases of P680+⋅ reduction by TyrZ are
slowed down from the hundreds of μs time range to the ms time range,
whereas both the S1TyrZ• → S2TyrZ and
the S3TyrZ• → S0TyrZ + O2
transition kinetics remained similar to those in PsbA(1/3)-PSII. These results
show that the geometry of the TyrZ phenol and its environment, likely
the Tyr-O···H···Nϵ-His bonding,
are modified in PsbA2-PSII when compared with PsbA(1/3)-PSII. They also point to
the dynamics of the proton-coupled electron transfer processes associated with
the oxidation of TyrZ being affected. From sequence comparison, we
propose that the C144P and P173M substitutions in PsbA2-PSII
versus PsbA(1/3)-PSII, respectively located upstream of the
α-helix bearing TyrZ and between the two α-helices
bearing TyrZ and its hydrogen-bonded partner, His-190, are
responsible for these changes. 相似文献
103.
Muraya MM de Villiers S Parzies HK Mutegi E Sagnard F Kanyenji BM Kiambi D Geiger HH 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2011,123(4):571-583
Wild sorghums are extremely diverse phenotypically, genetically and geographically. However, there is an apparent lack of
knowledge on the genetic structure and diversity of wild sorghum populations within and between various eco-geographical regions.
This is a major obstacle to both their effective conservation and potential use in breeding programs. The objective of this
study was to assess the genetic diversity and structure of wild sorghum populations across a range of eco-geographical conditions
in Kenya. Sixty-two wild sorghum populations collected from the 4 main sorghum growing regions in Kenya were genotyped using
18 simple sequence repeat markers. The study showed that wild sorghum is highly variable with the Coast region displaying
the highest diversity. Analysis of molecular variance showed a significant variance component within and among wild sorghum
populations within regions. The genetic structure of wild sorghum populations indicated that gene flow is not restricted to
populations within the same geographic region. A weak regional differentiation was found among populations, reflecting human
intervention in shaping wild sorghum genetic structure through seed-mediated gene flow. The sympatric occurrence of wild and
cultivated sorghums coupled with extensive seed-mediated gene flow, suggests a potential crop-to-wild gene flow and vice versa
across the regions. Wild sorghum displayed a mixed mating system. The wide range of estimated outcrossing rates indicate that
some environmental conditions may exist where self-fertilisation is favoured while others cross-pollination is more advantageous. 相似文献
104.
Anne-Laure Fauchais Marie-Claude Lise Pierre Marget Fran?ois-Xavier Lapeybie Holy Bezanahary Clothilde Martel Stéphanie Dumonteil Agnès Sparsa Fabrice Lalloué Kim Ly Marie Essig Elisabeth Vidal Marie-Odile Jauberteau 《PloS one》2013,8(11)
Background
Neurotrophins play a central role in the development and maintenance of the nervous system. However, neurotrophins can also modulate B and T cell proliferation and activation, especially via autocrine loops. We hypothesized that both serum and lymphocytic neurotrophin levels may be deregulated in systemic Lupus erythematosus (SLE) and may reflect clinical symptoms of the disease.Methods
Neurotrophins in the serum (ELISA tests) and lymphocytes (flow cytometry) were measured in 26 SLE patients and 26 control subjects. Th1 (interferon-γ) and Th2 (IL-10) profiles and serum concentration of BAFF were assessed by ELISA in the SLE and control subjects.Findings
We have demonstrated that both NGF and BDNF serum levels are higher in SLE patients than healthy controls (p=0.003 and p<0.001), independently of Th1 or Th2 profiles. Enhanced serum NT-3 levels (p=0.003) were only found in severe lupus flares (i.e. SLEDAI ≥ 10) and significantly correlated with complement activation (decreased CH 50, Γ=-0.28, p=0.03). Furthermore, there was a negative correlation between serum NGF levels and the number of circulating T regulatory cells (Γ=0.48, p=0.01). In circulating B cells, production of both NGF and BDNF was greater in SLE patients than in healthy controls. In particular, the number of NGF-secreting B cells correlated with decreased complement levels (p=0.05). One month after SLE flare treatment, BDNF levels decreased; in contrast, NGF and NT-3 levels remained unchanged.Conclusion
This study demonstrates that serum and B cell levels of both NGF and BDNF are increased in SLE, suggesting that the neurotrophin production pathway is deregulated in this disease. These results must be confirmed in a larger study with naive SLE patients, in order to avoid the potential confounding influence of prior immune-modulating treatments on neurotrophin levels. 相似文献105.
Sagnard F Deu M Dembélé D Leblois R Touré L Diakité M Calatayud C Vaksmann M Bouchet S Mallé Y Togola S Traoré PC 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2011,123(7):1231-1246
Gene flow between domesticated plants and their wild relatives is one of the major evolutionary processes acting to shape their structure of genetic diversity. Earlier literature, in the 1970s, reported on the interfertility and the sympatry of wild, weedy and cultivated sorghum belonging to the species Sorghum bicolor in most regions of sub-Saharan Africa. However, only a few recent surveys have addressed the geographical and ecological distribution of sorghum wild relatives and their genetic structure. These features are poorly documented, especially in western Africa, a centre of diversity for this crop. We report here on an exhaustive in situ collection of wild, weedy and cultivated sorghum assembled in Mali and in Guinea. The extent and pattern of genetic diversity were assessed with 15 SSRs within the cultivated pool (455 accessions), the wild pool (91 wild and weedy forms) and between them. F (ST) and R (ST) statistics, distance-based trees, Bayesian clustering methods, as well as isolation by distance models, were used to infer evolutionary relationships within the wild-weedy-crop complex. Firstly, our analyses highlighted a strong racial structure of genetic diversity within cultivated sorghum (F (ST) = 0.40). Secondly, clustering analyses highlighted the introgressed nature of most of the wild and weedy sorghum and grouped them into two eco-geographical groups. Such closeness between wild and crop sorghum could be the result of both sorghum's domestication history and preferential post-domestication crop-to-wild gene flow enhanced by farmers' practices. Finally, isolation by distance analyses showed strong spatial genetic structure within each pool, due to spatially limited dispersal, and suggested consequent gene flow between the wild and the crop pools, also supported by R (ST) analyses. Our findings thus revealed important features for the collection, conservation and biosafety of domesticated and wild sorghum in their centre of diversity. 相似文献
106.
Hélène Déméné Nathalie Jullian Nelly Morellet Hugues de Rocquigny Fabrice Cornille Bernard Maigret Bernard P. Roques 《Journal of biomolecular NMR》1994,4(2):153-170
Summary The nucleocapsid protein of Moloney murine leukemia virus (NCp10) is a 56-amino acid protein which contains one zinc finger of the CysX2CysX4HisX4Cys form, a highly conserved motif present in most retroviruses and retroelements. At pH5, NCp10 binds one zinc atom and the complexation induces a folding of the CysX2CysX4HisX4Cys box, similar to that observed for the zinc-binding domains of HIV-1 NC protein. The three-dimensional structure of NCp10 has been determined in aqueous solution by 600 MHz 1H NMR spectroscopy. The proton resonances could be almost completely assigned by means of phase-sensitive double-quantum-filtered COSY, TOCSY and NOESY techniques. NOESY spectra yielded 597 relevant structural constraints, which were used as input for distance geometry calculations with DIANA. Further refinement was performed by minimization with the program AMBER, which was modified by introducing a zinc force field. The solution structure is characterized by a well-defined central zinc finger (rmsd of 0.747±0.209 Å for backbone atoms and 1.709±0.187 Å when all atoms are considered), surrounded by flexible N- and C-terminal domains. The Tyr28, Trp35, Lys37, Lys41 and Lys42 residues, which are essential for activity, lie on the same face of the zinc finger, forming a bulge structure probably involved in viral RNA binding. The significance of these structural characteristics for the various biological functions of the protein is discussed, taking into account the results obtained with various mutants. 相似文献
107.
Adsorption of DNA to mica mediated by divalent counterions: a theoretical and experimental study
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Pastré D Piétrement O Fusil S Landousy F Jeusset J David MO Hamon L Le Cam E Zozime A 《Biophysical journal》2003,85(4):2507-2518
The adsorption of DNA molecules onto a flat mica surface is a necessary step to perform atomic force microscopy studies of DNA conformation and observe DNA-protein interactions in physiological environment. However, the phenomenon that pulls DNA molecules onto the surface is still not understood. This is a crucial issue because the DNA/surface interactions could affect the DNA biological functions. In this paper we develop a model that can explain the mechanism of the DNA adsorption onto mica. This model suggests that DNA attraction is due to the sharing of the DNA and mica counterions. The correlations between divalent counterions on both the negatively charged DNA and the mica surface can generate a net attraction force whereas the correlations between monovalent counterions are ineffective in the DNA attraction. DNA binding is then dependent on the fractional surface densities of the divalent and monovalent cations, which can compete for the mica surface and DNA neutralizations. In addition, the attraction can be enhanced when the mica has been pretreated by transition metal cations (Ni(2+), Zn(2+)). Mica pretreatment simultaneously enhances the DNA attraction and reduces the repulsive contribution due to the electrical double-layer force. We also perform end-to-end distance measurement of DNA chains to study the binding strength. The DNA binding strength appears to be constant for a fixed fractional surface density of the divalent cations at low ionic strength (I < 0.1 M) as predicted by the model. However, at higher ionic strength, the binding is weakened by the screening effect of the ions. Then, some equations were derived to describe the binding of a polyelectrolyte onto a charged surface. The electrostatic attraction due to the sharing of counterions is particularly effective if the polyelectrolyte and the surface have nearly the same surface charge density. This characteristic of the attraction force can explain the success of mica for performing single DNA molecule observation by AFM. In addition, we explain how a reversible binding of the DNA molecules can be obtained with a pretreated mica surface. 相似文献
108.
109.
The receptor Notch and its ligands of the Delta/Serrate/LAG2 (DSL) family are the central components in the Notch pathway, a fundamental cell signaling system that regulates pattern formation during animal development. Delta is directly ubiquitinated by Drosophila and Xenopus Neuralized, and by zebrafish Mind bomb, two unrelated RING-type E3 ubiquitin ligases with common abilities to promote Delta endocytosis and signaling activity. Although orthologs of both Neuralized and Mind bomb are found in most metazoan organisms, their relative contributions to Notch signaling in any single organism have not yet been assessed. We show here that a Drosophila ortholog of Mind bomb (D-mib) is a positive component of Notch signaling that is required for multiple Neuralized-independent, Notch-dependent developmental processes. Furthermore, we show that D-mib associates physically and functionally with both Serrate and Delta. We find that D-mib uses its ubiquitin ligase activity to promote DSL ligand activity, an activity that is correlated with its ability to induce the endocytosis and degradation of both Delta and Serrate (see also Le Borgne et al., 2005). We further demonstrate that D-mib can functionally replace Neuralized in multiple cell fate decisions that absolutely require endogenous Neuralized, a testament to the highly similar activities of these two unrelated ubiquitin ligases in regulating Notch signaling. We conclude that ubiquitination of Delta and Serrate by Neuralized and D-mib is an obligate feature of DSL ligand activation throughout Drosophila development. 相似文献
110.
Atassi F Brassart D Grob P Graf F Servin AL 《FEMS immunology and medical microbiology》2006,48(3):424-432
The purpose of this study was to investigate how human vaginal isolates of Lactobacillus acidophilus, Lactobacillus jensenii, Lactobacillus gasseri and Lactobacillus crispatus inhibit the vaginosis-associated pathogens Gardnerella vaginalis and Prevotella bivia. Results show that all the strains in coculture condition reduced the viability of G. vaginalis and P. bivia, but with differing degrees of efficacy. The treatment of G. vaginalis- and P. bivia-infected cultured human cervix epithelial HeLa cells with L. gasseri strain KS120.1 culture or cell-free culture supernatant (CFCS) results in the killing of the pathogens that are adhering to the cells. The mechanism of the killing activity is not attributable to low pH and the presence of lactic acid alone, but rather to the presence of hydrogen peroxide and proteolytic enzyme-resistant compound(s) present in the CFCSs. In addition, coculture of G. vaginalis or P. bivia with L. gasseri KS120.1 culture or KS120.1 bacteria results in inhibition of the adhesion of the pathogens onto HeLa cells. 相似文献