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171.
The peculiar heme pocket of the 2/2 hemoglobin of cold-adapted Pseudoalteromonas haloplanktis TAC125
Barry D. Howes Daniela Giordano Leonardo Boechi Roberta Russo Simona Mucciacciaro Chiara Ciaccio Federica Sinibaldi Maria Fittipaldi Marcelo A. Mart�� Dar��o A. Estrin Guido di Prisco Massimo Coletta Cinzia Verde Giulietta Smulevich 《Journal of biological inorganic chemistry》2011,16(2):299-311
The genome of the cold-adapted bacterium Pseudoalteromonas haloplanktis TAC125 contains multiple genes encoding three distinct monomeric hemoglobins exhibiting a 2/2 ??-helical fold. In the present work, one of these hemoglobins is studied by resonance Raman, electronic absorption and electronic paramagnetic resonance spectroscopies, kinetic measurements, and different bioinformatic approaches. It is the first cold-adapted bacterial hemoglobin to be characterized. The results indicate that this protein belongs to the 2/2 hemoglobin family, Group II, characterized by the presence of a tryptophanyl residue on the bottom of the heme distal pocket in position G8 and two tyrosyl residues (TyrCD1 and TyrB10). However, unlike other bacterial hemoglobins, the ferric state, in addition to the aquo hexacoordinated high-spin form, shows multiple hexacoordinated low-spin forms, where either TyrCD1 or TyrB10 can likely coordinate the iron. This is the first example in which both TyrCD1 and TyrB10 are proposed to be the residues that are alternatively involved in heme hexacoordination by endogenous ligands. 相似文献
172.
The cell wall binding domains (CBD) of bacteriophage endolysins target the enzymes to their substrate in the bacterial peptidoglycan with extraordinary specificity. Despite strong interest in these enzymes as novel antimicrobials, little is known regarding their interaction with the bacterial wall and their binding ligands. We investigated the interaction of Listeria phage endolysin PlyP35 with carbohydrate residues present in the teichoic acid polymers on the peptidoglycan. Biochemical and genetic analyses revealed that CBD of PlyP35 specifically recognizes the N-acetylglucosamine (GlcNAc) residue at position C4 of the polyribitol-phosphate subunits. Binding of CBDP35 could be prevented by removal of wall teichoic acid (WTA) polymers from cell walls, and inhibited by addition of purified WTAs or acetylated saccharides. We show that Listeria monocytogenes genes lmo2549 and lmo2550 are required for decoration of WTAs with GlcNAc. Inactivation of either gene resulted in a lack of GlcNAc glycosylation, and the mutants failed to bind CBDP35. We also report that the GlcNAc-deficient phenotype of L. monocytogenes strain WSLC 1442 is due to a small deletion in lmo2550, resulting in synthesis of a truncated gene product responsible for the glycosylation defect. Complementation with lmo2550 completely restored display of characteristic serovar 1/2 specific WTA and the wild-type phenotype. 相似文献
173.
We present two Bayesian procedures to infer the interactions and external currents in an assembly of stochastic integrate-and-fire
neurons from the recording of their spiking activity. The first procedure is based on the exact calculation of the most likely
time courses of the neuron membrane potentials conditioned by the recorded spikes, and is exact for a vanishing noise variance
and for an instantaneous synaptic integration. The second procedure takes into account the presence of fluctuations around
the most likely time courses of the potentials, and can deal with moderate noise levels. The running time of both procedures
is proportional to the number S of spikes multiplied by the squared number N of neurons. The algorithms are validated on synthetic data generated by networks with known couplings and currents. We also
reanalyze previously published recordings of the activity of the salamander retina (including from 32 to 40 neurons, and from
65,000 to 170,000 spikes). We study the dependence of the inferred interactions on the membrane leaking time; the differences
and similarities with the classical cross-correlation analysis are discussed. 相似文献
174.
Serini S Donato V Piccioni E Trombino S Monego G Toesca A Innocenti I Missori M De Spirito M Celleno L Fasano E Ranelletti FO Calviello G 《The Journal of nutritional biochemistry》2011,22(9):874-885
The dramatic increase in the incidence of nonmelanoma skin cancer over the last decades has been related to the augmented exposure to ultraviolet (UV) radiation (UVR). It is known that apoptosis is induced as a protective mechanism after the acute irradiation of keratinocytes, whereas apoptotic resistance and carcinogenesis may follow the chronic exposure to UVR. We found that not all the human keratinocytes lines studied underwent apoptosis following acute exposure to UVR (10-60 mJ/cm2). Whereas UVR induced apoptosis in the HaCaT cells, NCTC 2544 and nr-HaCaT cells showed apoptosis resistance. The cytokeratin pattern of the apoptosis-resistant cells indicated that they possessed a degree of differentiation lower than that of HaCaT cells. They also showed an enhanced expression of cyclooxygenase-2 (COX-2), an early marker of carcinogenesis in various tissues, including skin. n-3 polyunsaturated fatty acids have drawn increasing interest as nutritional factors with the potential to reduce UVR carcinogenesis, and since they are apoptosis inducers and COX-2 inhibitors in cancer cells, we investigated the ability of n-3 polyunsaturated fatty acids to influence the resistance to UVR-induced apoptosis in keratinocytes. We observed that docosahexaenoic acid (DHA) reverted the resistance of nr-HaCaT cells to UVR-induced apoptosis, increasing the Bax/Bcl-2 ratio and caspase-3 activity, and reduced COX-2 levels by inhibiting the expression of the human antigen R (HuR), a known COX-2 mRNA stabilizer in keratinocytes. The transfection of nr-HaCaT cells with HuR siRNA mimicked the proapoptotic effect of DHA. Overall, our findings further support the role of DHA as a suitable anticarcinogenic factor against nonmelanoma skin cancers. 相似文献
175.
Lloyd AJ William Allwood J Winder CL Dunn WB Heald JK Cristescu SM Sivakumaran A Harren FJ Mulema J Denby K Goodacre R Smith AR Mur LA 《The Plant journal : for cell and molecular biology》2011,67(5):852-868
In Arabidopsis, resistance to the necrotrophic fungus Botrytis cinerea is conferred by ethylene via poorly understood mechanisms. Metabolomic approaches compared the responses of the wild‐type, the ethylene‐insensitive mutant etr1‐1, which showed increased susceptibility, and the constitutively active ethylene mutants ctr1‐1 and eto2 both exhibited decreased susceptibility to B. cinerea. Fourier transform–infrared (FT‐IR) spectroscopy demonstrated reproducible biochemical differences between treatments and genotypes. To identify discriminatory mass‐to‐charge ratios (m/z) associated with resistance, discriminant function analysis was employed on spectra derived from direct injection electrospray ionisation‐mass spectrometry on the derived principal components of these data. Ethylene‐modulated m/z were mapped onto Arabidopsis biochemical pathways and many were associated with hydroxycinnamate and monolignol biosynthesis, both linked to cell wall modification. A high‐resolution linear triple quadrupole‐Orbitrap hybrid system confirmed the identity of key metabolites in these pathways. The contribution of these pathways to defence against B. cinerea was validated through the use of multiple Arabidopsis mutants. The FT‐IR microspectroscopy indicated that spatial accumulation of hydroxycinnamates and monolignols at the cell wall to confine disease was linked ot ethylene. These data demonstrate the power of metabolomic approaches in elucidating novel biological phenomena, especially when coupled to validation steps exploiting relevant mutant genotypes. 相似文献
176.
Biagio D’Aniello Irene Stanislao Simona Bonelli Emilio Balletto 《Biodiversity and Conservation》2011,20(8):1731-1744
Grasslands are usually the most suitable environment for butterflies, but have been also traditionally used for productive
activities. This paper compares the impact of mowing and grazing on butterfly biodiversity in two S Italian (Campania) grasslands,
at Campo Somma (CS) and Pianoro di Prada (PP) located at an identical altitude of 850 m. These grasslands have an area of
approximately 6 ha each and are at a 3 km distance from each other. They share similar climate and are both surrounded by
woods, mainly of sweet chestnut. CS is managed for haying and is mown once a year, in June. PP is used for sheep and cattle
grazing. Weekly transects were made from April to September in 2008 and 2009, during the butterfly flight activity. We analysed
data from eight monthly transects by Kruskal–Wallis and Mann–Whitney tests. We observed 45 butterfly species at PP, and 28
at CS. Diversity indexes were significantly higher at PP, whereas evenness was similar. The monthly comparisons of species
richness showed that, except for April, PP values were always significantly higher. Species abundance was significantly higher
at PP in June, July and August. In all months, except in April, the Shannon–Wiener index was also significantly higher at
PP, as was Simpson’s index in May, June and September. Dominance index differed significantly only in May, June and September,
whereas evenness was never significantly different between the two grasslands. These data show that, as concerns butterflies,
the impact of mowing was much stronger than that of grazing. 相似文献
177.
The study investigated the effect of feeding regime and sludge age on starch utilization. For this purpose, parallel sequencing batch reactors were operated with pulse and continuous feeding of soluble starch at sludge ages of 8 and 2 days. Pulse feeding induced almost complete conversion of starch to glycogen, while storage was lowered and accompanied with direct growth under continuous feeding, regardless of sludge age. Low sludge age did not alter simultaneous storage and utilization for direct growth but it slightly favoured direct utilization due to faster growing biomass. Experimental results suggested adsorption of starch onto biomass as a preliminary removal mechanism prior to hydrolysis at sludge age of 8 days. Adsorption was not noticeable as substrate removal, glycogen generation and dissolved oxygen decrease were synchronous at sludge age of 2 days. Bacterial community always included fractions storing glycogen although sludge age only affected the relative magnitude of filamentous growth. 相似文献
178.
In seed plant ovules, the diploid maternal sporophytic generation embeds and sustains the haploid generation (the female gametophyte);
thus, two independent generations coexist in a single organ. Many independent studies on Arabidopsis ovule mutants suggest that embryo sac development requires highly synchronized morphogenesis of the maternal sporophyte surrounding
the gametophyte, since megagametogenesis is severely perturbed in most of the known sporophytic ovule development mutants.
Which are the messenger molecules involved in the haploid–diploid dialogue? And furthermore, is this one way communication
or is a feedback cross talk? In this review, we discuss genetic and molecular evidences supporting the presence of a cross
talk between the two generations, starting from the first studies regarding ovule development and ending to the recently sporophytic
identified genes whose expression is strictly controlled by the haploid gametophytic generation. We will mainly focus on Arabidopsis studies since it is the species more widely studied for this aspect. Furthermore, possible candidate molecules involved in
the diploid–haploid generations dialogue will be presented and discussed. 相似文献
179.
180.
Ziv-Av A Taller D Attia M Xiang C Lee HK Cazacu S Finniss S Kazimirsky G Sarid R Brodie C 《Cellular signalling》2011,23(12):1936-1943
Gliomas are characterized by increased infiltration into the surrounding normal brain tissue. We recently reported that RTVP-1 is highly expressed in gliomas and plays a role in the migration of these cells, however the regulation of RTVP-1 expression in these cells is not yet described. In this study we examined the role of PKC in the regulation of RTVP-1 expression and found that PMA and overexpression of PKCα and PKCε increased the expression of RTVP-1, whereas PKCδ exerted an opposite effect. Using the MatInspector software, we identified a SRF binding site on the RTVP-1 promoter. Chromatin immunoprecipitation (ChIP) assay revealed that SRF binds to the RTVP-1 promoter in U87 cells, and that this binding was significantly increased in response to serum addition. Moreover, silencing of SRF blocked the induction of RTVP-1 expression in response to serum. We found that overexpression of PKCα and PKCε increased the activity of the RTVP-1 promoter and the binding of SRF to the promoter. In contrast, overexpression of PKCδ blocked the increase in RTVP-1 expression in response to serum and the inhibitory effect of PKCδ was abrogated in cells expressing a SRFT160A mutant. SRF regulated the migration of glioma cells and its effect was partially mediated by RTVP-1. We conclude that RTVP-1 is a PKC-regulated gene and that this regulation is at least partly mediated by SRF. Moreover, RTVP-1 plays a role in the effect of SRF on glioma cell migration. 相似文献