Purification and characterization of two cellobiohydrolases from Chaetomium thermophile var. coprophile

Cellobiohydrolases I and II were purified to homogeneity from culture filtrates of a thermophilic fungus, Chaetomium thermophile var. coprophile, by using a combination of ion-exchange and gel filtration chromatographic procedures. The molecular weights of cellobiohydrolase I and II were estimated to be 60000 and 40000 and the enzymes were found to be glycoproteins containing 17 and 22.8% carbohydrate, respectively. The two forms differed in their amino-acid composition mainly with respect to threonine, alanine, methionine and arginine. Antibodies produced against either form of cellobiohydrolases failed to cross-react with the other. The tryptic maps of the two enzymes were found to be different. The temperature optima for cellobiohydrolase I and II were 75 and 70°C, and they were optimally active at pH 5.8 and 6.4, respectively. Both enzymes were stable at higher temperatures and were able to degrade crystalline cellulosic materals.

Purification and functional characteristics of an endocellulase from Chaetomium thermophile var. coprophile

An endocellulase (1→4)-β-d-glucan 4-glucanohydrolase was isolated from the culture filtrates of Chaetomium thermophile. The enzyme was homogeneous by PAGE and SDS-PAGE. The molecular weight was 36 000 by SDS-PAGE and 38 000 by gel filtration. It was a glycoprotein. From the amino acid composition, it was found to be rich in glycine, threonine, and aspartic and glutamic acids, but contained only low proportions of histidine and sulfur-containing amino acids. It was optimally active at pH 6 and at 60°. The enzyme did not hydrolyze cellobiose and cellotriose, but hydrolyzed cello-tetraose, -pentaose, and -hexaose at comparable rates. It was specific for molecules containing β-(1→4) linkages. It showed high activity towards amorphous cellulose, and the reaction products contained cellobiose to cellopentaose, showing that it effects random cleavage of cellulose.

Purification and characterization of an extracellular β-glucosidase from the thermophilic fungus Sporotrichum thermophile and its influence on cellulase activity

Multiple forms of beta-glucosidase (EC 3.2.1.21) of Sporotrichum thermophile were produced when the fungus was grown in a cellulose medium. One beta-glucosidase was purified 16-fold from 6-d-old culture filtrates by ion-exchange and gel-filtration chromatography. The purified enzyme was free of cellulase activity. It hydrolysed aryl beta-D-glucosides and beta-D-linked diglucosides. It was optimally active at pH 5.4, at 65-degrees-C. The apparent K(m) values for p-nitrophenyl beta-D-glucoside (PNPG) and cellobiose were 0.29 and 0.83 mm, respectively. Glucose, fucose, nojirimycin and gluconolactone inhibited beta-glucosidase competitively. At high (> 1 mm) substrate concentration, beta-glucosidase catalysed a parallel transglycosylation reaction. The transglycosylation product formed from cellobiose appeared to be a beta-linked tetramer of glucose. Admixtures of beta-glucosidase and cellulase components showed that the concept of cellobiose inhibition of cellulases was not valid for all components of the cellulase system of S. thermophile. Beta-Glucosidase supplementation also stimulated cellulose hydrolysis by cellulases when there was no accumulation of cellobiose in reaction mixture.

Localization and release of ?-glucosidase in the thermophilic and cellulolytic fungus, Sporotrichum thermophile

In a medium containing cellulose as the carbon source, the rapid growth of Sporotrichum thermophile, the secretion of cellulases and the utilization of cellulose were well-correlated events. The production of beta-glucosidase in culture medium lagged behind cellulases, coinciding with the time of extensive autolysis of mycelia. By contrast, neither apparent autolysis nor secretion of beta-glucosidase occurred when S. thermophile was grown in medium containing cellobiose; the enzyme activity remained associated with mycelia. The release of beta-glucosidase in cellulose-grown cultures was correlated with the activity of the lytic enzyme in the cell wall. Immunocytochemical localization and biochemical characterization showed that a beta-glucosidase released in the cellulose medium was the same as that which remained associated with mycelia grown on cellobiose. The results indicated that the release of beta-glucosidase in the cellulose culture is incidental to the activity of the lytic enzymes which are strongly induced by cellulose. The observations minimize a functional role of the culture fluid beta-glucosidase in cellulolysis by the fungus. Rather, the available information suggests that the cellulases and beta-glucosidases associated with the hyphal cell wall may play a role in cellulolysis by the fungus. (C) 1994 Academic Press, Inc.

Localization and release of β-glucosidase in the thermophilic and cellulolytic fungus, Sporotrichum thermophile

n a medium containing cellulose as the carbon source, the rapid growth of Sporotrichum thermophile, the secretion of cellulases and the utilization of cellulose were well-correlated events. The production of beta-glucosidase in culture medium lagged behind cellulases, coinciding with the time of extensive autolysis of mycelia. By contrast, neither apparent autolysis nor secretion of beta-glucosidase occurred when S. thermophile was grown in medium containing cellobiose; the enzyme activity remained associated with mycelia. The release of beta-glucosidase in cellulose-grown cultures was correlated with the activity of the lytic enzyme in the cell wall. Immunocytochemical localization and biochemical characterization showed that a beta-glucosidase released in the cellulose medium was the same as that which remained associated with mycelia grown on cellobiose. The results indicated that the release of beta-glucosidase in the cellulose culture is incidental to the activity of the lytic enzymes which are strongly induced by cellulose. The observations minimize a functional role of the culture fluid beta-glucosidase in cellulolysis by the fungus. Rather, the available information suggests that the cellulases and beta-glucosidases associated with the hyphal cell wall may play a role in cellulolysis by the fungus. (C) 1994 Academic Press, Inc.

Comparative analysis of thermophilic and mesophilic proteins using Protein Energy Networks

Background: Thermophilic proteins sustain themselves and function at higher temperatures. Despite their structural and functional similarities with their mesophilic homologues, they show enhanced stability. Various comparative studies at genomic, protein sequence and structure levels, and experimental works highlight the different factors and dominant interacting forces contributing to this increased stability. Methods: In this comparative structure based study, we have used interaction energies between amino acids, to generate structure networks called as Protein Energy Networks (PENs). These PENs are used to compute network, sub-graph, and node specific parameters. These parameters are then compared between the thermophile-mesophile homologues. Results: The results show an increased number of clusters and low energy cliques in thermophiles as the main contributing factors for their enhanced stability. Further more, we see an increase in the number of hubs in thermophiles. We also observe no community of electrostatic cliques forming in PENs. Conclusion: In this study we were able to take an energy based network approach, to identify the factors responsible for enhanced stability of thermophiles, by comparative analysis. We were able to point out that the sub-graph parameters are the prominent contributing factors. The thermophiles have a better-packed hydrophobic core. We have also discussed how thermophiles, although increasing stability through higher connectivity retains conformational flexibility, from a cliques and communities perspective.

Comparative analysis of thermophilic and mesophilic proteins using Protein Energy Networks

Background: Thermophilic proteins sustain themselves and function at higher temperatures. Despite their structural and functional similarities with their mesophilic homologues, they show enhanced stability. Various comparative studies at genomic, protein sequence and structure levels, and experimental works highlight the different factors and dominant interacting forces contributing to this increased stability. Methods: In this comparative structure based study, we have used interaction energies between amino acids, to generate structure networks called as Protein Energy Networks (PENs). These PENs are used to compute network, sub-graph, and node specific parameters. These parameters are then compared between the thermophile-mesophile homologues. Results: The results show an increased number of clusters and low energy cliques in thermophiles as the main contributing factors for their enhanced stability. Further more, we see an increase in the number of hubs in thermophiles. We also observe no community of electrostatic cliques forming in PENs. Conclusion: In this study we were able to take an energy based network approach, to identify the factors responsible for enhanced stability of thermophiles, by comparative analysis. We were able to point out that the sub-graph parameters are the prominent contributing factors. The thermophiles have a better-packed hydrophobic core. We have also discussed how thermophiles, although increasing stability through higher connectivity retains conformational flexibility, from a cliques and communities perspective.

Expanding the repertoire of DNA-mediated signaling in DNA repair

DNA damage is extremely detrimental to the cell and must be repaired to protect the genome. DNA is capable of conducting charge through the overlapping π-orbitals of stacked bases; this phenomenon is extremely sensitive to the integrity of the π-stack, as perturbations attenuate DNA charge transport (CT). Based on the E. coli base excision repair (BER) proteins EndoIII and MutY, it has recently been proposed that redox-active proteins containing metal clusters can utilize DNA CT to signal one another to locate sites of DNA damage.

To expand our repertoire of proteins that utilize DNA-mediated signaling, we measured the DNA-bound redox potential of the nucleotide excision repair (NER) helicase XPD from Sulfolobus acidocaldarius. A midpoint potential of 82 mV versus NHE was observed, resembling that of the previously reported BER proteins. The redox signal increases in intensity with ATP hydrolysis in only the WT protein and mutants that maintain ATPase activity and not for ATPase-deficient mutants. The signal increase correlates directly with ATP activity, suggesting that DNA-mediated signaling may play a general role in protein signaling. Several mutations in human XPD that lead to XP-related diseases have been identified; using SaXPD, we explored how these mutations, which are conserved in the thermophile, affect protein electrochemistry.

To further understand the electrochemical signaling of XPD, we studied the yeast S. cerevisiae Rad3 protein. ScRad3 mutants were incubated on a DNA-modified electrode and exhibited a similar redox potential to SaXPD. We developed a haploid strain of S. cerevisiae that allowed for easy manipulation of Rad3. In a survival assay, the ATPase- and helicase-deficient mutants show little survival, while the two disease-related mutants exhibit survival similar to WT. When both a WT and G47R (ATPase/helicase deficient) strain were challenged with different DNA damaging agents, both exhibited comparable survival in the presence of hydroxyurea, while with methyl methanesulfonate and camptothecin, the G47R strain exhibits a significant change in growth, suggesting that Rad3 is involved in repairing damage beyond traditional NER substrates. Together, these data expand our understanding of redox-active proteins at the interface of DNA repair.

Carboxydothermus hydrogenoformans comme catalyseur biologique pour la conversion du monoxyde de carbone en hydrogène simultanément a la minéralisation de calcium et phosphate

La gazéification est aujourd'hui l'une des stratégies les plus prometteuses pour valoriser les déchets en énergie. Cette technologie thermo-chimique permet une réduction de 95 % de la masse des intrants et génère des cendres inertes ainsi que du gaz de synthèse (syngaz). Le syngaz est un combustible gazeux composé principalement de monoxyde de carbone (CO), d'hydrogène (H2) et de dioxyde de carbone (CO2). Le syngaz peut être utilisé pour produire de la chaleur et de l'électricité. Il est également la pierre angulaire d'un grand nombre de produits à haute valeur ajoutée, allant de l'éthanol à l'ammoniac et l'hydrogène pur. Les applications en aval de la production de syngaz sont dictées par son pouvoir calorifique, lui-même dépendant de la teneur du gaz en H2. L’augmentation du contenu du syngaz en H2 est rendu possible par la conversion catalytique à la vapeur d’eau, largement répandu dans le cadre du reformage du méthane pour la production d'hydrogène. Au cours de cette réaction, le CO est converti en H2 et CO2 selon : CO + H2O → CO2 + H2. Ce processus est possible grâce à des catalyseurs métalliques mis en contact avec le CO et de la vapeur. La conversion catalytique à la vapeur d’eau a jusqu'ici été réservé pour de grandes installations industrielles car elle nécessite un capital et des charges d’exploitations très importantes. Par conséquent, les installations de plus petite échelle et traitant des intrants de faible qualité (biomasse, déchets, boues ...), n'ont pas accès à cette technologie. Ainsi, la seule utilisation de leur syngaz à faible pouvoir calorifique, est limitée à la génération de chaleur ou, tout au plus, d'électricité. Afin de permettre à ces installations une gamme d’application plus vaste de leurs syngaz, une alternative économique à base de catalyseur biologique est proposée par l’utilisation de bactéries hyperthermophiles hydrogénogènes. L'objectif de cette thèse est d'utiliser Carboxydothermus hydrogenoformans, une bactérie thermophile carboxydotrophe hydrogénogène comme catalyseur biologique pour la conversion du monoxyde de carbone en hydrogène. Pour cela, l’impact d'un phénomène de biominéralisation sur la production d’H2 a été étudié. Ensuite, la faisabilité et les limites de l’utilisation de la souche dans un bioréacteur ont été évaluées. Tout d'abord, la caractérisation de la phase inorganique prédominante lorsque C. hydrogenoformans est inoculé dans le milieu DSMZ, a révélé une biominéralisation de phosphate de calcium (CaP) cristallin en deux phases. L’analyse par diffraction des rayons X et spectrométrie infrarouge à transformée de Fourier de ce matériau biphasique indique une signature caractéristique de la Mg-whitlockite, alors que les images obtenues par microscopie électronique à transmission ont montré l'existence de nanotiges cristallines s’apparentant à de l’hydroxyapatite. Dans les deux cas, le mode de biominéralisation semble être biologiquement induit plutôt que contrôlé. L'impact du précipité de CaP endogène sur le transfert de masse du CO et la production d’H2 a ensuite été étudié. Les résultats ont été comparés aux valeurs obtenues dans un milieu où aucune précipitation n'est observée. Dans le milieu DSMZ, le KLa apparent (0.22 ± 0.005 min-1) et le rendement de production d’H2 (89.11 ± 6.69 %) étaient plus élevés que ceux obtenus avec le milieu modifié (0.19 ± 0.015 min-1 et 82.60 ± 3.62% respectivement). La présence du précipité n'a eu aucune incidence sur l'activité microbienne. En somme, le précipité de CaP offre une nouvelle stratégie pour améliorer les performances de transfert de masse du CO en utilisant les propriétés hydrophobes de gaz. En second lieu, la conversion du CO en H2 par la souche Carboxydothermus hydrogenoformans fut étudiée et optimisée dans un réacteur gazosiphon de 35 L. Parmi toutes les conditions opérationnelles, le paramètre majeur fut le ratio du débit de recirculation du gaz sur le débit d'alimentation en CO (QR:Qin). Ce ratio impacte à la fois l'activité biologique et le taux de transfert de masse gaz-liquide. En effet, au dessus d’un ratio de 40, les performances de conversion du CO en H2 sont limitées par l’activité biologique alors qu’en dessous, elles sont limitées par le transfert de masse. Cela se concrétise par une efficacité de conversion maximale de 90.4 ± 0.3 % et une activité spécifique de 2.7 ± 0.4 molCO·g–1VSS·d–1. Malgré des résultats prometteurs, les performances du bioréacteur ont été limitées par une faible densité cellulaire, typique de la croissance planctonique de C. hydrogenoformans. Cette limite est le facteur le plus contraignant pour des taux de charge de CO plus élevés. Ces performances ont été comparées à celles obtenues dans un réacteur à fibres creuses (BRFC) inoculé par la souche. En dépit d’une densité cellulaire et d’une activité volumétrique plus élevées, les performances du BRFC à tout le moins cinétiquement limitées quand elles n’étaient pas impactées par le transfert de masse, l'encrassement et le vieillissement de la membrane. Afin de parer à la dégénérescence de C. hydrogenoformans en cas de pénurie de CO, la croissance de la bactérie sur pyruvate en tant que seule source de carbone a été également caractérisée. Fait intéressant, en présence simultanée de pyruvate et de CO, C. hydrogenoformans n’a amorcé la consommation de pyruvate qu’une fois le CO épuisé. Cela a été attribué à un mécanisme d'inhibition du métabolisme du pyruvate par le CO, faisant ainsi du pyruvate le candidat idéal pour un système in situ de secours.

The mechanism of bacterial indigo reduction

The reduction of water-insoluble indigo by the recently isolated moderate thermophile, Clostridium isatidis, has been studied with the aim of developing a sustainable technology for industrial indigo reduction. The ability to reduce indigo was not shared with C. aurantibutyricum, C. celatum and C. papyrosolvens, but C. papyrosolvens could reduce indigo carmine (5,5-indigosulfonic acid), a soluble indigo derivative. The supernatant from cultures of C. isatidis, but not from cultures of the other bacteria tested, decreased indigo particle size to one-tenth diameter. Addition of madder powder, anthraquinone-2,6-disulfonic acid, and humic acid all stimulated indigo reduction by C. isatidis. Redox potentials of cultures of C. isatidis were about 100 mV more negative than those of C. aurantibutyricum, C. celatum and C. papyrosolvens, and reached –600 mV versus the SCE in the presence of indigo, but potentials were not consistently affected by the addition of the quinone compounds, which probably act by modifying the surface of the bacteria or indigo particles. It is concluded that C. isatidis can reduce indigo because (1) it produces an extracellular factor that decreases indigo particle size, and (2) it generates a sufficiently reducing potential.

Crystallization of the secondary alcohol dehydrogenase from Thermoanaerobacter ethanolicus 39E.

The secondary alcohol dehydrogenase from the thermophile Thermoanaerobacter ethanolicus 39E has been crystallized at 40 degrees C by vapour difussion using polyethelene glycol as a precipitant. The orthorhombic crystals belong to the space group P 2(1)2(1)2 with cell constants of a=170.0 Angstrom, b=125.7 Angstrom and c=80.5 Angstrom. A native X-ray diffraction data set has been collected to 2.7 Angstrom resolution.

Online Dictionary of Invertebrate Zoology: T

tabula tabular tachyauxesis tachyblastic tachygen tachygenesis tachytelic tactic tactile tactoreceptors taenia taeniate taenidium taenioglossate tagma tagmata tagmosis tail tailfan Takakura's talon talus tandem tangent tangoreceptor tanylobous tapetal tapetum tapinoma-odor Tardigrada tardigrades tarsal tarsation tarsite tarsomere tarsungulus tarsus taste tautonomy tautonym taxa taxes taxis taxis taxodont taxometrics taxon taxonomic taxonomist taxonomy tectiform tectostracum tectum teeth teges tegillum tegmen tegmentum tegula tegular tegulum tegumen tegument tegumentary tela telaform telamon telegonic teleiochrysalis telenchium teleoconch teleodont teleology teleotrocha telepod telescope telescopic teletrophic telioderma teliophan telmophage telocentric telodendria telofemur telogonic telolecithal telomitic telophase telophragma telopod telopodite telorhabdions telosonic telostome telosynapsis telosyndesis telotarsus telotaxis telotroch telson template temporal tenacipeds tenaculum tenent teneral tensor tentacle tentacular tentaculocyst tentaculozooid tentilla tentorial tentorium tenuous teratocyte teratogen teratogenesis teratogyne teratology terebella terebra terebrant terebrate teres terete terga tergal tergite tergolateral tergopleural tergopore tergum tergum termen terminal terminalia termitarium termitophile terranes terrestrial terricolous territory tertiary tertibrach tertibrachial tessellate test testaceology testaceous test-cross testes testis testisac testudinate tetanus tetany tetractinal tetractine tetrad tetradelphic tetramerous tetramorphic tetraploid tetrapod tetrapterous tetrasomic tetrathyridial tetrathyridium tetraxon tetraxonid thalassophilous thallus thamnophilous thanatocoenosis thanatosis theca thecae thecal thecate thelycum thelygenesis thelygenous thelyotokous thelyotoky theory thermocline thermophile thermophobe thermoreceptor thermotaxis thickness thigmotactic thigmotaxis thigmotropism third-form thoraces thoracic thoracomere thoracopod(ite) thorax thoraxes thread thylacium thylacogen thyridial thyridium thyroid thysanuriform tibia tibial tibiotarsal tibiotarsus Tiedemann's tiled timbal tinctorial tine tissue tissue titilla titillae titillator tocopherol tocospermal tocospermia tocostome tokostome tomentose tomentum Tomosvary tone tonic tonofibrillae tonus topochemical topogamodeme topomorph topomorphic toponym topotype tori torma tormogen tornote tornus torose torpid torqueate torsion tortuose torulose torus totipotent totomount toxa toxicognath toxicology toxin toxinosis toxoglossate toxoid trabecula trabeculate trabeculated trachea tracheae tracheal tracheate tracheoblast tracheolar tracheoles trachychromatic tract Tragardh's tragus transad transcoxa transcurrent transect transection transformation transient transitional translocation translucent transmission transposed transscutal transstadial transtilla transverse trapeziform trapezium trapezoid trema tremata Trematoda trenchant trepan triact triactinal triad triaene triage triangle triangular triangulate triaulic triaxial triaxon tribe tribocytic trichite trichobothrium trichobranchia trichobranchiate trichocerous trichodes trichodeum trichodragmata trichogen trichoid trichomes trichophore trichopore trichosors trichostichal trichotomous trichroism tricolumella tricomes tricostate tricrepid tricuspid tricuspidate tridactyl trident tridentate trifid trifurcate triglycerides trignathan trigonal trigoneutism trilabiate trilateral trilobate trilocular trimorphic trimorphism Trinominal triordinal tripartite tripectinate triplet triploblastic triploid triquetral triquetrous triradiate triradiates tritocerebral tritocerebrum tritocerebrum tritonymph tritosternum triturate triungulin triungulinid trivial trivium trivoltine trixenic troch trochal trochalopodous trochantellus trochanter trochanteral trochantin trochi trochiform trochlea trocholophous trochophore trochosphere trochus troglobiont troglodytic troglophile trogloxene tropeic trophal trophallactic trophallaxis trophamnion trophi trophic trophidium trophobiont trophobiont trophobiosis trophobiotic trophocytes trophodisc trophogeny trophoporic trophorhinium trophosome trophotaxis trophothylax trophozooid trophus tropis tropism tropotaxis trumpet truncate truncation trunk trypsin tryptic tryptophan tryptophane T-tubule tube tube-feet tubercle tubercula tuberculate tuberculose tuberiferous tubicolous tubifacient tubule tubulus tubus tuft Tullgren tumefaction tumescence tumid tumulus tunic tunica tunicary tunicate turbinate turgid turreted turriculate tychoparthenogenesis tylasters tylenchoid tyli tyloid tyloides tylosis tylostyle tylote tylus tymbal tympanal tympanal tympanic tympanum Tyndall type typhlosole typologist typolysis typostasis

Bindeprotein-abhängige DctS-Sensorkinasen aus Bacillus subtilis und Geobacillus kaustophilus

Das Enterobakterium Escherichia coli sowie das Bodenbakterium Bacillus subtilis können C4-Dicarbonsäuren als aerobe Kohlenstoffquelle zur Energiekonservierung nutzen. Die Regulation des C4-Dicarboxylatstoffwechsels erfolgt in E. coli und B. subtilis durch das Zweikomponentensystem DcuSREc bzw. DctSRBs, bestehend aus einer Sensorkinase und einem Responseregulator. Diese kontrollieren die Expression des C4-Dicarboxylat-Transporters DctA. Der Sensor DcuSEc benötigt für seine Funktion im aeroben Stoffwechsel den Transporter DctA als Cosensor. Für das DctSRBs-System gibt es Hinweise aus genetischen Untersuchungen, dass DctSBs das Bindeprotein DctBBs und möglicherweise auch DctABs als Cosensoren für seine Funktion benötigt. In dieser Arbeit sollte ein direkter Nachweis geführt werden, ob DctBBs und DctABs gemeinsam oder nur jeweils eine der Komponenten als Cosensoren für DctSBs fungieren. Sowohl für DctBBs als auch für DctABs wurde eine direkte Protein-Protein-Interaktion mit DctSBs durch zwei in vivo Interaktionsmethoden nachgewiesen. Beide Methoden beruhen auf der Co-Reinigung der Interaktionspartner mittels Affinitätschromatographie und werden je nach Affinitätssäule als mSPINE oder mHPINE (Membrane Strep/His-Protein INteraction Experiment) bezeichnet. Die Interaktion von DctSBs mit DctBBs wurde zusätzlich über ein bakterielles Two-Hybrid System nachgewiesen. Nach Coexpression mit DctSBs interagieren DctABs und DctBBs in mSPINE-Tests gleichzeitig mit der Sensorkinase. DctSBs bildet somit eine sensorische DctS/DctA/DctB-Einheit in B. subtilis und das Bindeprotein DctBBs agiert nur als Cosensor, nicht aber als Transport-Bindeprotein. Eine direkte Interaktion zwischen dem Transporter DctABs und dem Bindeprotein DctBBs besteht nicht. Transportmessungen belegen, dass der DctA-vermittelte Transport von [14C]-Succinat unabhängig ist von DctBBs. Außerdem wurde untersucht, ob Zweikomponentensysteme aus anderen Bakteriengruppen nach einem ähnlichen Schema wie DcuSREc bzw. DctSRBs aufgebaut sind. Das thermophile Bakterium Geobacillus kaustophilus verfügt über ein DctSR-System, welches auf genetischer Ebene mit einem Transporter des DctA-Typs und einem DctB-Bindeprotein geclustert vorliegt. Die Sensorkinase DctSGk wurde in E. coli heterolog exprimiert und gereinigt. Diese zeigt in einer E. coli DcuS-Insertionsmutanten Komplementation der DcuS-Funktion und besitzt dabei Spezifität für die C4-Dicarbonsäuren Malat, Fumarat, L-Tartrat und Succinat sowie für die C6-Tricarbonsäure Citrat. In Liposomen rekonstituiertes DctSGk zeigt Autokinase-Aktivität nach Zugabe von [γ-33P]-ATP. Der KD-Wert für [γ-33P]-ATP der Kinasedomäne von DctSGk liegt bei 43 μM, die Affinität für ATP ist damit etwa 10-fach höher als in DcuSEc.

Analysis of the Heat-Shock Response Displayed by Two Chaetomium Species Originating from Different Thermal Environments

Three features of the heat shock response, reorganization of protein expression, intracellular accumulation of trehalose, and alteration in unsaturation degree of fatty acids were investigated in the thermophilic fungus Chaetomium thermophile and compared to the response displayed by a closely related mesophilic species, C. brasiliense. Thermophilic heat shock response paralleled the mesophilic response in many respects like (i) the temperature difference observed between normothermia and the upper limit of translational activity, (ii) the transient nature of the heat shock response at the level of protein expression including both the induction of heat shock proteins (HSPs) as well as the repression of housekeeping proteins, (iii) the presence of representatives of high-molecular-weight {HSPs} families, (iv) intracellular accumulation of trehalose, and finally (v) modifications in fatty acid composition. On the other hand, a great variability between the two organisms was observed for the proteins expressed during stress, in particular a protein of the {HSP60} family that was only observed in C. thermophile. This peptide was also present constitutively at normal temperature and may thus fulfil thermophilic functions. It is shown that accumulation of trehalose does not play a part in thermophily but is only a stress response. C. thermophile contains less polyunsaturated fatty acids at normal temperature than C. brasiliense, a fact that can be directly related to thermophily. When subjected to heat stress, both organisms tended to accumulate shorter and less unsaturated fatty acids.

North Atlantic (Rockall Plateau) coccolith assemblage data for MIS 5 of ODP Hole 162-980B

Calcareous nannoplankton analyses on late quaternary sediments from the eastern North Atlantic ODP Site 980 (55°29'N, 14°42'W) provide detailed insight into palaeoceanographic and palaeoclimatic changes that occurred throughout the Termination II and the adjacent interglacial of the Marine Isotope Stage (MIS) 5. This study presents the development of the coccolith assemblage throughout the interglacial MIS 5 towards the beginning of the glacial MIS 4 in the vicinity of the Rockall Plateau and investigates and characterises the impact of climatic and environmental variations on the coccolith assemblage distribution between 135 and 65 ky. In general, the coccolith assemblage is dominated by Gephyrocapsa muellerae and Emiliania huxleyi, whilst significant changes in palaeoceanographic and palaeoclimatic conditions are mainly shown by variations of subordinate species. A drastic increase in coccolith accumulation rates and a change from a less to a higher diverse species assemblage indicate a rapid increase in surface water temperatures during the onset of MIS 5 from c. 127.5 ky on. Highest coccolith numbers, high numbers of taxa and a large diversity indicate highest coccolithophore primary productivity and peak interglacial conditions during MIS 5.5, which are due to the high influence of relatively warm surface water to this region. Coccolith numbers peak again around 120 ky and decline afterwards but stay above glacial levels. The two cooling events of MIS 5.4 and 5.2 interrupt the generally warm conditions and are indicated by lowered coccolith numbers, a drop of thermophile species and a reduction of the species diversity. Decreasing coccolith numbers and a slightly reduced diversity indicate that environmental conditions deteriorated towards the onset of MIS 4. The analysis of the coccolith assemblage reveals that not only the stadial events MIS 5.4 and 5.2 are characterised by colder conditions, but furthermore confirms the upcoming notion that MIS 5.5 was terminated by a slight short-term cooling of the surface water which occurred around 124 ky.