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91.
Dé E Saint N Glinel K Meli AC Lévy D Jacob-Dubuisson F 《Molecular membrane biology》2008,25(3):192-202
Autotransporters are a superfamily of proteins secreted by Gram-negative bacteria including many virulence factors. They are modular proteins composed of an N-terminal signal peptide, a surface-exposed 'passenger' domain carrying the activity of the protein, and a C-terminal 'translocator' domain composed of an alpha-helical linker region and a transmembrane beta-barrel. The translocator domain plays an essential role for the secretion of the passenger domain across the outer membrane; however, the mechanism of autotransport remains poorly understood. The whooping cough agent Bordetella pertussis produces an autotransporter serine-protease, SphB1, which is involved in the maturation of an adhesin at the bacterial surface. SphB1 also mediates the proteolytic maturation of its own precursor. We used SphB1 as a model autotransporter and performed the first comparisons of the biochemical and biophysical properties of an isolated translocator domain with those of the same domain preceded by the C-terminal moiety of its natural passenger. By using cross-linking and dynamic light scattering, we provide evidence that the passenger domain promotes the auto-association of SphB1, although these interactions appear rather labile. Electrophysiological studies revealed that the passenger domain of the autotransporter appears to maintain the translocator channel in a low-conductance conformation, most likely by stabilizing the alpha-helix inside the pore. That the passenger may significantly influence AT physicochemical properties is likely to be relevant for the in vivo maturation and stability of AT proteins. 相似文献
92.
There is a major need to understand the historical condition and chemical/biological functions of the ecosystems following a conversion of wetlands to agricultural functions. To better understand the dynamics of soil total organic carbon (TOC) and phosphorus (P) during beef cattle pastures to wetland reconversion, soil core samples were collected from the beef cattle pasture and from the natural wetland at Plant City, FL, during five summer seasons (2002–2007). The levels of TOC and soil P were significantly affected by changing land use and hydrology. Draining natural wetlands to grazed pastures resulted in very pronounced reduction of TOC from 180.1 to 5.4 g g?1. Cumulative concentrations of total phosphorus (TP) in soils (1134 mg kg?1) under drained condition are two to three times lower than those in soils (2752 mg kg?1) under flooded condition over the periods of land use reconversion. There was a declining trend (r = 0.82**; p ≤ 0.01) in total soil P from natural wetland (763 mg kg?1) to altered pastures (340 mg kg?1), largely as organic-bound P (natural wetland, 48%; grazed pastures, 44%; altered pastures, 29%). These results are important in establishing baseline information on soil properties in pasture and wetland prior to restoring and reconverting pasture back to wetland conditions. The results further suggest that changes in soil properties due to changing land use and hydrologic conditions (drying and re-wetting) could be long lasting. 相似文献
93.
Albano C. Meli Maria Kondratova Virginie Molle Laurent Coquet Andrey V. Kajava Nathalie Saint 《The Journal of membrane biology》2009,230(3):143-154
Attachment to host tissues is a critical step in the pathogenesis of most bacterial infections. Enterotoxigenic Escherichia coli (ETEC) remains one of the principal causes of infectious diarrhea in humans. The recent identification of additional ETEC
surface molecules suggests that new targets may be exploited in vaccine development. The EtpA protein identified in ETEC H10407
is a large glycosylated adhesin secreted via the two-partner secretion system. EtpA requires its putative partner EtpB for
translocation across the outer membrane (OM). We investigated the biochemical and electrophysiological properties of purified
EtpB. We showed that EtpB is 65-kDa heat-modifiable protein localized to the OM. Electrophysiological experiments indicated
that EtpB is able to form pores in planar lipid bilayer membranes with an asymmetric current, suggesting its functional asymmetry.
The pore of EtpB frequently assumes an opened conformation and fluctuates between three well-defined conductance states. In
silico analysis of the EtpB amino acid sequence and molecular modeling suggest that EtpB is similar to the well-known TpsB
protein FhaC from Bordetella pertussis and has a C-terminal transmembrane β-barrel domain that is occluded by an N-terminal α-helix, an extracellular loop, and
two periplasmic polypeptide-transport-associated (POTRA) domains. Together, these data confirm that EtpB is a pore-forming
protein mainly folded into a β-barrel conformation and indicate that EtpB presents typical features of the OM TpsB proteins. 相似文献
94.
Environmental shaping of sponge associated archaeal communities 总被引:1,自引:0,他引:1
Turque AS Batista D Silveira CB Cardoso AM Vieira RP Moraes FC Clementino MM Albano RM Paranhos R Martins OB Muricy G 《PloS one》2010,5(12):e15774
Background
Archaea are ubiquitous symbionts of marine sponges but their ecological roles and the influence of environmental factors on these associations are still poorly understood.Methodology/Principal Findings
We compared the diversity and composition of archaea associated with seawater and with the sponges Hymeniacidon heliophila, Paraleucilla magna and Petromica citrina in two distinct environments: Guanabara Bay, a highly impacted estuary in Rio de Janeiro, Brazil, and the nearby Cagarras Archipelago. For this we used metagenomic analyses of 16S rRNA and ammonia monooxygenase (amoA) gene libraries. Hymeniacidon heliophila was more abundant inside the bay, while P. magna was more abundant outside and P. citrina was only recorded at the Cagarras Archipelago. Principal Component Analysis plots (PCA) generated using pairwise unweighted UniFrac distances showed that the archaeal community structure of inner bay seawater and sponges was different from that of coastal Cagarras Archipelago. Rarefaction analyses showed that inner bay archaeaoplankton were more diverse than those from the Cagarras Archipelago. Only members of Crenarchaeota were found in sponge libraries, while in seawater both Crenarchaeota and Euryarchaeota were observed. Although most amoA archaeal genes detected in this study seem to be novel, some clones were affiliated to known ammonia oxidizers such as Nitrosopumilus maritimus and Cenarchaeum symbiosum.Conclusion/Significance
The composition and diversity of archaeal communities associated with pollution-tolerant sponge species can change in a range of few kilometers, probably influenced by eutrophication. The presence of archaeal amoA genes in Porifera suggests that Archaea are involved in the nitrogen cycle within the sponge holobiont, possibly increasing its resistance to anthropogenic impacts. The higher diversity of Crenarchaeota in the polluted area suggests that some marine sponges are able to change the composition of their associated archaeal communities, thereby improving their fitness in impacted environments. 相似文献95.
Jacob B Landis Christopher M Miller Amanda K Broz Alexandra A Bennett Noelia Carrasquilla-Garcia Douglas R Cook Robert L Last Patricia A Bedinger Gaurav D Moghe 《Molecular biology and evolution》2021,38(8):3202
Evolutionary dynamics at the population level play a central role in creating the diversity of life on our planet. In this study, we sought to understand the origins of such population-level variation in mating systems and defensive acylsugar chemistry in Solanum habrochaites—a wild tomato species found in diverse Andean habitats in Ecuador and Peru. Using Restriction-site-Associated-DNA-Sequencing (RAD-seq) of 50 S. habrochaites accessions, we identified eight population clusters generated via isolation and hybridization dynamics of 4–6 ancestral populations. Detailed characterization of mating systems of these clusters revealed emergence of multiple self-compatible (SC) groups from progenitor self-incompatible populations in the northern part of the species range. Emergence of these SC groups was also associated with fixation of deleterious alleles inactivating acylsugar acetylation. The Amotape-Huancabamba Zone—a geographical landmark in the Andes with high endemism and isolated microhabitats—was identified as a major driver of differentiation in the northern species range, whereas large geographical distances contributed to population structure and evolution of a novel SC group in the central and southern parts of the range, where the species was also inferred to have originated. Findings presented here highlight the role of the diverse ecogeography of Peru and Ecuador in generating population differentiation, and enhance our understanding of the microevolutionary processes that create biological diversity. 相似文献
96.
Mark R.J. Elsegood Noelia M. Sanchez-Ballester Martin B. Smith 《Inorganica chimica acta》2011,379(1):115
The three-step synthesis of new mixed P/N/N′/O-donor ligands C6H3(OH){2-NHC(O)CH2NCHC6H4PPh2}(4-CH3) 3a·HH and C6H4(OH){3-NHC(O)CH2NCHC6H4PPh2} 3b·HH, by Schiff base condensation of the 1° amines C6H3(OH){2-NHC(O)CH2NH2}(4-CH3) 2a or C6H4(OH){3-NHC(O)CH2NH2} 2b with C6H4(CHO)(2-PPh2) in refluxing EtOH, is described. Reaction of 1 equiv. of 3a·HH or 3b·HH with MCl2(cod) (M = Pt, Pd; cod = cycloocta-1,5-diene) affords the κ2-PN-chelate complexes MCl2(3a·HH) (M = Pd 4a; M = Pt 4b) and MCl2(3b·HH) (M = Pt 4c). The dichlorometal(II) complexes 4d and 4e, bearing instead a pendant 4-phenolic group, were similarly prepared (in >90% yield). Chloro-bridge cleavage of [Pd(μ-Cl)(η3-C3H5)]2 with 3a·HH or 3b·HH gave the monocationic κ2-PN-chelate complexes [Pd(η3-C3H5)(3a·HH)]Cl 5a or [Pd(η3-C3H5)(3b·HH)]Cl 5b, respectively. Elimination of cod, and single CH3 protonation, from Pt(CH3)2(cod) upon reaction with 1 equiv. of 3a·HH or 3b·HH in C7H8 at room temperature afforded the neutral complexes C6H3(OH){2-NC(O)CH2NCHC6H4PPh2Pt(CH3)}(4-CH3) 6a and C6H4(OH){3-NC(O)CH2NCHC6H4PPh2Pt(CH3)} 6b, respectively bearing a monoanionic (3a·H− or 3b·H−) κ3-PNN′-tridentate ligand. Amide and phenol deprotonation were readily achieved, using KOtBu as base, to give high yields of the κ4-PNN′O-tetradentate complexes C6H3(O){2-NC(O)CH2NCHC6H4PPh2Pd}(4-CH3) 7a and C6H3(O){2-NC(O)CH2NCHC6H4PPh2Pt}(4-CH3) 7b bearing the dianionic ligand 3a2−. All new compounds have been characterised by multinuclear NMR, FTIR, mass spectroscopy and microanalysis. Single crystal X-ray studies have been performed on compounds 1b·1.5CH2Cl2, 3b·HH·0.5Et2O, 6b·CHCl3 and 7b·0.5Et2O. 相似文献
97.
98.
Martín MC Pant N Ladero V Günaydin G Andersen KK Alvarez B Martínez N Alvarez MA Hammarström L Marcotte H 《Applied and environmental microbiology》2011,77(6):2174-2179
A series of expression cassettes which mediate secretion or surface display of antibody fragments was stably integrated in the chromosome of Lactobacillus paracasei. L. paracasei producing surface-anchored variable domain of llama heavy chain (VHH) (ARP1) directed against rotavirus showed efficient binding to rotavirus and protection in the mouse model of rotavirus infection. 相似文献
99.
Arcucci A Ruocco MR Amatruda N Riccio A Tarantino G Albano F Mele V Montagnani S 《Journal of biological regulators and homeostatic agents》2011,25(4):647-654
Systemic sclerosis (SSc) is a chronic disease of connective tissue characterized by vascular damage, autoantibody production and extensive fibrosis of skin, skeletal muscles, vessels and visceral organs. Fibrosis is a biological process involving inflammatory response and reactive oxygen species (ROS) accumulation leading to fibroblast activation. Extracellular superoxide dismutase (SOD3), a copper and zinc superoxide dismutase, which is expressed in selected tissues, is secreted into the extracellular space and catalyzes the dismutation of superoxide radical to hydrogen peroxide and molecular oxygen. Moreover, SOD3 is associated to inflammatory responses in some experimental models. In this paper we analysed, by RT-PCR and immunofluorescence, SOD3 expression and intracellular localization in dermal fibroblasts from both healthy donors and patients affected by diffuse form of SSc. Moreover, we determined SOD3 enzymatic activity in fibroblast culture medium with the xanthine/xanthine oxidase method. Increased expression of SOD3 mRNA was detected in systemic sclerosis fibroblasts (SScF), as compared to control healthy fibroblasts (HF), and SOD3 immunofluorescence staining displayed a characteristic pattern of secretory proteins in both HF and SScF. Superoxide dismutase assay demonstrated that SOD3 enzymatic activity in SScF culture medium is four times more than in HF culture medium. These data suggest that an alteration in SOD3 expression and activity could be associated to SSc fibrosis. 相似文献
100.
E. Albano Pérez J.A. Coetzee T. Ruiz Téllez M.P. Hill 《South African Journal of Botany》2011,77(3):795-800
We investigated water hyacinth seed banks in several aquatic systems in South Africa. Fifteen sites, mainly in the Eastern and Western Cape provinces, were surveyed from August to October 2009. Soil seed density varied between 0 and 2534 seeds/m2 but did not differ significantly between the type of waterbody (impoundment vs. river) or the history of control carried out at a site. Average germination was 54.17% with very fast velocities (Vigour Index = 36.66) and maximum germination around three days. Although we demonstrated the existence of an important reservoir of seeds, results from this study indicated that a combination of factors such as water fluctuation, eutrophication and seed decomposition might have had a great influence on dispersal and persistence of seeds. 相似文献