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991.
Colussi F Garcia W Rosseto FR de Mello BL de Oliveira Neto M Polikarpov I 《European biophysics journal : EBJ》2012,41(1):89-98
Due to its elevated cellulolytic activity, the filamentous fungus Trichoderma harzianum (T. harzianum) has considerable potential in biomass hydrolysis application. Cellulases from Trichoderma reesei have been widely used in studies of cellulose breakdown. However, cellulases from T. harzianum are less-studied enzymes that have not been characterized biophysically and biochemically as yet. Here, we examined the effects
of pH and temperature on the secondary and tertiary structures, compactness, and enzymatic activity of cellobiohydrolase Cel7A
from T. harzianum (Th Cel7A) using a number of biophysical and biochemical techniques. Our results show that pH and temperature perturbations affect
Th Cel7A stability by two different mechanisms. Variations in pH modify protonation of the enzyme residues, directly affecting
its activity, while leading to structural destabilization only at extreme pH limits. Temperature, on the other hand, has direct
influence on mobility, fold, and compactness of the enzyme, causing unfolding of Th Cel7A just above the optimum temperature limit. Finally, we demonstrated that incubation with cellobiose, the product of
the reaction and a competitive inhibitor, significantly increased the thermal stability of Th Cel7A. Our studies might provide insights into understanding, at a molecular level, the interplay between structure and activity
of Th Cel7A at different pH and temperature conditions. 相似文献
992.
Bultot L Guigas B Von Wilamowitz-Moellendorff A Maisin L Vertommen D Hussain N Beullens M Guinovart JJ Foretz M Viollet B Sakamoto K Hue L Rider MH 《The Biochemical journal》2012,443(1):193-203
Recombinant muscle GYS1 (glycogen synthase 1) and recombinant liver GYS2 were phosphorylated by recombinant AMPK (AMP-activated protein kinase) in a time-dependent manner and to a similar stoichiometry. The phosphorylation site in GYS2 was identified as Ser7, which lies in a favourable consensus for phosphorylation by AMPK. Phosphorylation of GYS1 or GYS2 by AMPK led to enzyme inactivation by decreasing the affinity for both UDP-Glc (UDP-glucose) [assayed in the absence of Glc-6-P (glucose-6-phosphate)] and Glc-6-P (assayed at low UDP-Glc concentrations). Incubation of freshly isolated rat hepatocytes with the pharmacological AMPK activators AICA riboside (5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside) or A769662 led to persistent GYS inactivation and Ser7 phosphorylation, whereas inactivation by glucagon treatment was transient. In hepatocytes from mice harbouring a liver-specific deletion of the AMPK catalytic α1/α2 subunits, GYS2 inactivation by AICA riboside and A769662 was blunted, whereas inactivation by glucagon was unaffected. The results suggest that GYS inactivation by AMPK activators in hepatocytes is due to GYS2 Ser7 phosphorylation. 相似文献
993.
Caraci F Battaglia G Sortino MA Spampinato S Molinaro G Copani A Nicoletti F Bruno V 《Neurochemistry international》2012,61(4):559-565
Moving from early studies, we here review the most recent evidence linking metabotropic glutamate (mGlu) receptors to processes of neurodegeneration/neuroprotection. The use of knockout mice and subtype-selective drugs has increased our knowledge of the precise role played by individual mGlu receptor subtypes in these processes. Activation of mGlu1 and mGlu5 receptors may either amplify or reduce neuronal damage depending on the context and the nature of the toxic insults. In contrast, mGlu1 and mGlu5 receptors antagonists are consistently protective in in vitro and in vivo models of neuronal death. A series of studies suggest that mGlu1 receptor antagonists or negative allosteric modulators (NAMs) are promising candidates for the treatment of ischemic brain damage, whereas mGlu5 receptor NAMs, which have been clinically developed for the treatment of Parkinson's disease (PD) and l-DOPA-induced dyskinesias, protect nigro-striatal dopaminergic neurons against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) toxicity in mice and monkeys. Activation of glial mGlu3 receptors promotes the formation of various neurotrophic factors, such as transforming growth factor-β (TGF-β), glial-derived neurotrophic factor (GDNF), nerve growth factor (NGF), and brain-derived neurotrophic factor (BDNF). Hence, selective mGlu3 receptor agonists or positive allosteric modulators (PAMs) (not yet available) are potentially helpful in the treatment of chronic neurodegenerative disorders such as PD, Alzheimer's disease (AD), and amyotrophic lateral sclerosis. Selective mGlu2 receptor PAMs should be used with caution in AD patients because these drugs are shown to amplify β-amyloid neurotoxicity. Finally, mGlu4 receptor agonists/PAMs share with mGlu5 receptor NAMs the ability to improve motor symptoms associated with PD and attenuate nigro-striatal degeneration at the same time. No data are yet available on the role of mGlu7 and mGlu8 receptors in neurodegeneration/neuroprotection. 相似文献
994.
Ivy RA Ranieri ML Martin NH den Bakker HC Xavier BM Wiedmann M Boor KJ 《Applied and environmental microbiology》2012,78(6):1853-1864
Psychrotolerant spore-forming bacteria represent a major challenge to the goal of extending the shelf life of pasteurized dairy products. The objective of this study was to identify prominent phylogenetic groups of dairy-associated aerobic sporeformers and to characterize representative isolates for phenotypes relevant to growth in milk. Analysis of sequence data for a 632-nucleotide fragment of rpoB showed that 1,288 dairy-associated isolates (obtained from raw and pasteurized milk and from dairy farm environments) clustered into two major divisions representing (i) the genus Paenibacillus (737 isolates, including the species Paenibacillus odorifer, Paenibacillus graminis, and Paenibacillus amylolyticus sensu lato) and (ii) Bacillus (n = 467) (e.g., Bacillus licheniformis sensu lato, Bacillus pumilus, Bacillus weihenstephanensis) and genera formerly classified as Bacillus (n = 84) (e.g., Viridibacillus spp.). When isolates representing the most common rpoB allelic types (ATs) were tested for growth in skim milk broth at 6°C, 6/9 Paenibacillus isolates, but only 2/8 isolates representing Bacillus subtypes, grew >5 log CFU/ml over 21 days. In addition, 38/40 Paenibacillus isolates but only 3/47 Bacillus isolates tested were positive for β-galactosidase activity (including some isolates representing Bacillus licheniformis sensu lato, a common dairy-associated clade). Our study confirms that Paenibacillus spp. are the predominant psychrotolerant sporeformers in fluid milk and provides 16S rRNA gene and rpoB subtype data and phenotypic characteristics facilitating the identification of aerobic spore-forming spoilage organisms of concern. These data will be critical for the development of detection methods and control strategies that will reduce the introduction of psychrotolerant sporeformers and extend the shelf life of dairy products. 相似文献
995.
Identification of Avian pathogenic Escherichia coli genes that are induced in vivo during infection in chickens 总被引:2,自引:0,他引:2
Tuntufye HN Lebeer S Gwakisa PS Goddeeris BM 《Applied and environmental microbiology》2012,78(9):3343-3351
Avian pathogenic Escherichia coli (APEC) is associated with extraintestinal infections in poultry causing a variety of diseases collectively known as colibacillosis. The host and bacterial factors influencing and/or responsible for carriage and systemic translocation of APEC inside the host are poorly understood. Identification of such factors could help in the understanding of its pathogenesis and in the subsequent development of control strategies. Recombination-based in vivo expression technology (RIVET) was used to identify APEC genes specifically expressed during infection in chickens. A total of 21 clones with in vivo-induced promoters were isolated from chicken livers and spleens, indicative of systemic infection. DNA sequencing of the cloned fragments revealed that 12 of the genes were conserved E. coli genes (metH, lysA, pntA, purL, serS, ybjE, ycdK [rutC], wcaJ, gspL, sdsR, ylbE, and yjiY), 6 of the genes were phage related/associated, and 3 genes were pathogen specific (tkt1, irp2, and eitD). These genes are involved in various cellular functions, such as metabolism, cell envelope and integrity, transport systems, and virulence. Others were phage related or have yet-unknown functions. 相似文献
996.
Alien molluscs affect the composition and diversity of native macroinvertebrates in a sandy flat of Lake Neuchâtel,Switzerland 总被引:4,自引:0,他引:4
The spread of alien molluscs is a serious threat to native biodiversity in fresh waters. Alien freshwater molluscs may deplete
the resources of native species and alter the physical structure of the habitat through their shell mass. These changes might
have both positive and negative effects on native community members. We investigated the native macroinvertebrate community
in relation to the densities of four alien mollusc species (Corbicula fluminea, Dreissena polymorpha, Potamopyrgus antipodarum and Lithoglyphus naticoides) in a sandy flat of Lake Neuchatel, Switzerland. The habitat examined was dominated by these alien mollusc species. The abundance
of the alien molluscs did not directly impact the native community assembly. However, C. fluminea and D. polymorpha influenced the composition and diversity of native macroinvertebrates by transforming the sandy substratum into a partly
hard substratum habitat. Substantial differences in community composition between shallow (<3.5 m) and (≥5 m) deep sites were
recorded. At shallow sites, the abundance of D. polymorpha was significantly reduced as a result of depth-selective feeding of ducks. A controlled shell decay study revealed that shells
of alien molluscs (C. fluminea, D. polymorpha) persist for a longer period in the sediment than those of native molluscs. Consequently, shells of alien molluscs have a
long-lasting impact by modifying the sandy habitat. This form of ecosystem engineering favours the occurrence of several native
taxa, but is disadvantageous for other taxa with specific habitat requirements, and thus can be regarded as an indirect impact
of competition. 相似文献
997.
Amari M Laguerre S Vuillemin M Robert H Loux V Klopp C Morel S Gabriel B Remaud-Siméon M Gabriel V Moulis C Fontagné-Faucher C 《Journal of bacteriology》2012,194(6):1608-1609
Weissella confusa is a rod-shaped heterofermentative lactic acid bacterium from the family of Leuconostocaceae. Here we report the draft genome sequence of the strain W. confusa LBAE C39-2 isolated from a traditional French wheat sourdough. 相似文献
998.
Emmanuel Serrano Ferron Hélène Verheyden Jürgen Hummel Bruno Cargnelutti Bruno Lourtet Joel Merlet Mónica González-Candela Jean Marc Angibault Aidan Jonathan Mark Hewison Marcus Clauss 《Ecological Research》2012,27(1):77-82
Digestive plasticity, which refers to changes in digestive features due to changes in both internal and external environmental
conditions, is a crucial factor for understanding the ability of species to cope with environmental changes. In Europe, agricultural
intensification and the loss of forests have been major challenges for original forest dwellers, however some species, such
as the European roe deer (Capreolus capreolus), have been able to successfully colonize these new habitats. In this work, we investigated the adaptation of some digestive
features of roe deer to the agricultural landscapes. We assessed whether changes in local landscape structure influenced the
mass of both reticulorumen (RR) and distal fermentation chamber (DFC) of 47 juvenile and adult roe deer inhabiting an agro-ecosystem
in southwest France. Woodland cover had a clear effect on diet quality (estimated by the rate of gas production of digestive
contents) and DFC weight of animals. In fact, deer from the most forested landscapes showed heavier DFCs and fed on poorer
quality diet (lower gas production) than their counterparts from the most open landscapes. RR mass was less influenced by
the landscape openness, being the age of animals the main factor for understanding the variations of this digestive feature
in our study area. We can conclude that colonizing agricultural landscapes increases the access to highly energetic and digestive
resources. 相似文献
999.
In mammals, milk provision is crucial to offspring survival and growth from birth to weaning. Milk deficiency early in life may cause death or changes in the progeny metabolism that later may lead to obesity and metabolic disorders. This study investigates milk ejection (ME) the first day after birth (D1) in F2 females from the intercross of LG/J and SM/J inbred mice strains. The absence of milk in F3 pups?? stomach at D1 is directly associated with their survival (p?<?0.001) and growth pattern (p?<?0.001) in the early stages of life. Furthermore, late growth pattern is also affected by this lack of nutrients at D1 because pups that survive this absence, mostly males, are heavier at weaning (p?<?0.001) which, after necropsy, is shown to be due to significant higher total fat deposition (p?<?0.01). We performed QTL analysis for ME at D1 in these F2 females. Maternal performance of ME revealed a complex genetic architecture which even though it contains only a single QTL (accounting for 8?% of the variation in ME), it is totally context-dependent on the genetic background. We discovered many regions involved in epistatic interactions that together with the single QTL explain 19?% of the genetic variation for this trait. Milk ejection is an important component of maternal care, and understanding the mechanisms modulating its variation, along with other maternal features, may help to disentangle the complexity that is the mother/offspring relationship. 相似文献
1000.
Gualano B Everaert I Stegen S Artioli GG Taes Y Roschel H Achten E Otaduy MC Junior AH Harris R Derave W 《Amino acids》2012,43(1):21-24
Carnosine is present in high concentrations in skeletal muscle where it contributes to acid buffering and functions also as a natural protector against oxidative and carbonyl stress. Animal studies have shown an anti-diabetic effect of carnosine supplementation. High carnosinase activity, the carnosine degrading enzyme in serum, is a risk factor for diabetic complications in humans. The aim of the present study was to compare the muscle carnosine concentration in diabetic subjects to the level in non-diabetics. Type 1 and 2 diabetic patients and matched healthy controls (total n=58) were included in the study. Muscle carnosine content was evaluated by proton magnetic resonance spectroscopy (3 Tesla) in soleus and gastrocnemius. Significantly lower carnosine content (-45%) in gastrocnemius muscle, but not in soleus, was shown in type 2 diabetic patients compared with controls. No differences were observed in type 1 diabetic patients. Type II diabetic patients display a reduced muscular carnosine content. A reduction in muscle carnosine concentration may be partially associated with defective mechanisms against oxidative, glycative and carbonyl stress in muscle. 相似文献