bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biochemical analysis of a thermostable tryptophan synthase from a hyperthermophilic archaeon
Authors: Tang Xiao‐Feng , Ezaki Satoshi , Atomi Haruyuki , Imanaka Tadayuki 
Published: March 2003

Pyridoxal 5′‐phosphate‐dependent tryptophan synthase catalyzes the last two reactions of tryptophan biosynthesis, and is comprised of two distinct subunits, α and β. TktrpA and TktrpB, which encode the α subunit and β subunit of tryptophan synthase from a hyperthermophilic archaeon, Thermococcus kodakaraensis KOD1, were independently expressed in Escherichia coli and their protein products were purified. Tryptophan synthase complex (Tk‐TS complex), obtained by heat treatment of a mixture of the cell‐free extracts containing each subunit, was also purified. Gel‐filtration chromatography revealed that Tk‐TrpA was a monomer (α), Tk‐TrpB was a dimer (β2), and Tk‐TS complex was a tetramer (α2β2). The Tk‐TS complex catalyzed the overall αβ reaction with a specific activity of 110 µmol Trp per µmol active site per min under its optimal conditions (80 °C, pH 8.5). Individual activity of the α and β reactions of the Tk‐TS complex were 8.5 µmol indole per µmol active site per min (70 °C, pH 7.0) and 119 µmol Trp per µmol active site per min (90 °C, pH 7.0), respectively. The low activity of the α reaction of the Tk‐TS complex indicated that turnover of the β reaction, namely the consumption of indole, was necessary for efficient progression of the α reaction. The α and β reaction activities of independently purified Tk‐TrpA and Tk‐TrpB were 10‐fold lower than the respective activities detected from the Tk‐TS complex, indicating that during heat treatment, each subunit was necessary for the other to obtain a proper conformation for high enzyme activity. Tk‐TrpA showed only trace activities at all temperatures examined (40–85 °C). Tk‐TrpB also displayed low levels of activity at temperatures below 70 °C. However, Tk‐TrpB activity increased at temperatures above 70 °C, and eventually at 100 °C, reached an equivalent level of activity with the β reaction activity of Tk‐TS complex. Taking into account the results of circular dichroism analyses of the three enzymes, a model is proposed which explains the relationship between structure and activity of the α and β subunits with changes in temperature. This is the first report of an archaeal tryptophan synthase, and the first biochemical analysis of a thermostable tryptophan synthase at high temperature.
Peroxovanadate induces tyrosine phosphorylation of phosphoinositide‐dependent protein kinase‐1
Authors: Grillo Sophie , Grémeaux Thierry , Casamayor Antonio , Alessi Dario R , Le Marchand‐Brustel Yannick , Tanti Jean‐François 
Published: March 2003

Phosphoinositide‐dependent protein kinase‐1 (PDK1) is a recently identified kinase that phosphorylates and activates protein kinase B (PKB). Activation of PKB by insulin is linked to its translocation from the cytosol to the plasma membrane. However, no data are available yet concerning the localization of PDK1 in insulin‐sensitive tissue. Using isolated adipocytes, we studied the effect of insulin and of an insulin‐mimicking agent peroxovanadate on the subcellular localization of PDK1. In unstimulated adipocytes, overexpressed PDK1 was mostly cytosolic with a low amount associated to membranes. Peroxovanadate stimulation induced the redistribution of PDK1 to the membranes while insulin was without effect. This peroxovanadate effect was dependent on phosphatidylinositol 3,4,5 triphosphate [PtdIns(3,4,5)P3] production as inhibition of PtdIns 3‐kinase by wortmannin or deletion of the PH domain of PDK1 prevented the peroxovanadate‐induced translocation of PDK1. Further, peroxovanadate‐treatment induced a tyrosine phosphorylation of PDK1 which was wortmannin insensitive and did not require the PH domain of PDK1. An inhibitor of Src kinase (PP2) decreased the peroxovanadate‐induced PDK1 tyrosine phosphorylation and overexpression of v‐Src stimulated this phosphorylation. Mutation of tyrosine 373 of PDK1 abolished the v‐Src induced PDK1 tyrosine phosphorylation and partially reduced the effect of peroxovanadate. Our findings suggest that PDK1 could be a substrate for tyrosine kinases and identify Src kinase as one of the tyrosine kinases able to phosphorylate PDK1.
Characterization of the general odorant‐binding protein 2 in the molecular coding of odorants in Mamestra brassicae
Authors: Jacquin‐Joly Emmanuelle , Bohbot Jonathan , Francois Marie‐Christine , Cain Anne‐Hélène , Nagnan‐Le Meillour Patricia 
Published: March 2003

The general odorant‐binding protein 2 of Mamestra brassicae males has been purified from antennal extracts and examined in binding assays with pheromone components of this species and a behavioral antagonist, cis‐11‐hexadecenol. The protein showed high affinity for the latter compound and no affinity for the pheromone components. In addition, expression of the protein, studied by in situ hybridization, was restricted to the long sensilla trichodea, which house the neuron that responds to cis‐11‐hexadecenol. The expression in a functionally defined population of sensilla, together with binding specificity and previous electrophysiological data, suggest an unsuspected role for the general odorant‐binding protein 2 in M. brassicae. It may be involved in the transduction process for the behavioral antagonist to which neurons are specifically tuned and always cocompartmentalized in long trichodeal hairs, with neurons responding to the major pheromonal compound, cis‐11‐hexadecenyl acetate. These data are consistent with the involvement of odorant‐binding proteins in the fine discrimination between pheromone and antagonist, which is related to avoidance of interspecific mating mistakes.
Glycoinositolphosphosphingolipids (basidiolipids) of higher mushrooms
Authors: Jennemann Richard , Geyer Rudolf , Sandhoff Roger , Gschwind Ruth M. , Levery Steven B. , Gröne Hermann‐Josef , Wiegandt Herbert 
Published: March 2003

The basidiolipids of six mushroom species, i.e. the basidiomycetes Amanita virosa (engl., death cup), Calvatia exipuliformis (engl., puffball), Cantharellus cibarius (engl., chanterelle), Leccinum scabrum (engl., red birch boletus), Lentinus edodes (jap., Shiitake), and Pleurotus ostreatus (engl., oystermushroom), were isolated, and their chemical structures investigated. All glycolipids are structurally related to those of the Agaricales (engl., field mushroom). They are glycoinositolphosphosphingolipids, their ceramide moiety consisting of t18:0‐trihydroxysphinganine and an α‐hydroxy long‐chain fatty acid. In contrast to a previous study [Jennemann, R., Bauer, B.L., Bertalanffy, H., Geyer, R., Gschwind, R.M., Selmer, T. & Wiegandt, H. (1999) Eur. J. Biochem.259, 331–338], the glycoside anomery of the hexose (mannose) connected to the inositol of all investigated basidiomycete glycolipids, including the basidiolipids of Agaricus bisporus, was determined unequivocally to be alpha. Therefore, the root structure of all basidiolipids consists of α‐dManp‐2Ins1‐[PO4]‐Cer. In addition, for some mushroom species, the occurrence of an inositol substitution position variant, α‐Manp‐4Ins1‐[PO4]‐Cer, is shown. The carbohydrate of chanterelle basidiolipids consists solely of mannose, i.e. Cc1, Manα‐3 or ‐6Manα; Cc2, Manα‐3(Manα‐6)Manα‐. All other species investigated show extension of the α‐mannoside in the 6‐position by β‐galactoside, which, in some instances, is α‐fucosylated in 2‐position (Fucα‐2)Galβ‐6Manα‐. Further sugar chain elongation at the β‐galactoside may be in 3‐ and/or 6‐position by α‐galactoside, e.g. Ce4, Po2, Galα‐3‐(Galα‐6)(Fucα‐2)Galβ‐6Manα‐, whereas A. virosa, Av‐3, has a more complex, highly α‐fucosylated terminus, Galα‐3 (Fucα‐2)(Fucα‐6)Galα‐2(Galα‐3)Galβ‐6Manα‐. L. edodes basidiolipids show further elongation by α‐mannoside, e.g. Le3, Manα‐2Manα‐6Galα‐3(Fucα‐2)Galβ‐6Manα‐, C. exipuliformis glycolipid by α‐glucoside, i.e. Ce3, Glcα‐6Galβ‐6Manα‐. Basidiolipid Ls1 from L. scabrum, notably, has a 3‐α‐mannosylated α‐fucose, i.e. Galα‐6(Manα‐3Fucα‐2)Galα‐6Galβ‐6Manα‐. In conclusion, basidiolipids, though identical in their ceramide constitution, display wide and systematic mushroom species dependent variabilities of their chemical structures.
Identification and characterization of SEB, a novel protein that binds to the acute undifferentiated leukemia‐associated protein SET
Authors: Minakuchi Masayoshi , Kakazu Naoki , Gorrin‐Rivas Manuel J. , Abe Tatsuo , Copeland Terry D. , Ueda Kunihiro , Adachi Yoshifumi 
Published: March 2003

SET, the translocation breakpoint‐encoded protein in acute undifferentiated leukemia (AUL), is a 39‐kDa nuclear phosphoprotein and has an inhibitory activity for protein phosphatase 2A (PP2A). SET is fused to a putative oncoprotein, CAN/NUP214, in AUL and is thought to play a key role in leukemogenesis by its nuclear localization, protein–protein interactions and PP2A inhibitory activity. Here, we describe the isolation and characterization of a novel cDNA encoding a protein with 1542 amino‐acid residues that specifically interacts in a yeast two‐hybrid system as well as in human cells with SET. This new protein, which we name SEB (SET‐binding protein), is identified as a 170‐kDa protein by immunoprecipitation with a specific antibody and is localized predominantly in the nucleus. SEB1238–1434 is determined as a SET‐binding region that specifically binds to SET182–223. SEB also has an oncoprotein Ski homologous region (amino acids 654–858), six PEST sequences and three sequential PPLPPPPP repeats at the C‐terminus. SEB mRNA is expressed ubiquitously in all human adult tissues and cells examined. The SEB gene locus is assigned to the chromosome 18q21.1 that contains candidate tumor suppressor genes associated with deletions in cancer and leukemia. Although the function of SEB is not known, we propose that SEB plays a key role in the mechanism of SET‐related leukemogenesis and tumorigenesis, perhaps by suppressing SET function or by regulating the transforming activity of Ski in the nucleus.
Biosynthesis of terpenoids
Authors: Rohdich Felix , Eisenreich Wolfgang , Wungsintaweekul Juraithip , Hecht Stefan , Schuhr Christoph A. , Bacher Adelbert 
Published: March 2003

The putative catalytic domain of an open reading frame from Plasmodium falciparum with similarity to the ispF gene of Escherichia coli specifying 2C‐methyl‐d‐erythritol 2,4‐cyclodiphosphate synthase was expressed in a recombinant E. coli strain. The recombinant protein was purified to homogeneity and was found to catalyze the formation of 2C‐methyl‐d‐erythritol 2,4‐cyclodiphosphate from 4‐diphosphocytidyl‐2C‐methyl‐d‐erythritol 2‐phosphate at a rate of 4.3 µmol·mg−1·min−1. At lower rates, the recombinant protein catalyzes the formation of 2‐phospho‐2C‐methyl‐d‐erythritol 3,4‐cyclophosphate from 4‐diphosphocytidyl‐2C‐methyl‐d‐erythritol 2‐phosphate and the formation of 2C‐methyl‐d‐erythritol 3,4‐cyclophosphate from 4‐diphosphocytidyl‐2C‐methyl‐d‐erythritol. Divalent metal ions such as magnesium or manganese are required for catalytic activity. The enzyme has a pH optimum at pH 7.0. Recombinant expression of the full‐length open reading frame afforded insoluble protein that could not be folded in vitro. The enzyme is a potential target for antimalarial drugs directed at the nonmevalonate pathway of isoprenoid biosynthesis.
Catalytic selenols couple the redox cycles of metallothionein and glutathione
Authors: Chen Yu , Maret Wolfgang 
Published: March 2003

Co‐ordination of zinc to the thiol group of cysteine allows mobilization of zinc through oxidation of its ligand. This molecular property links the binding and release of zinc in metallothionein (MT) to the cellular redox state [Maret W. & Vallee B.L. (1998) Proc. Natl Acad. Sci. USA95, 3483–3488]. Biological disulfides such as glutathione disulfide (GSSG) oxidize MT with concomitant release of zinc, while glutathione (GSH) reduces the oxidized protein to thionein, which then binds to available zinc. Neither of these two redox processes is very efficient, even at high concentrations of GSSG or GSH. However, the GSH/GSSG redox pair can efficiently couple with the MT/thionein system in the presence of a selenium compound that has the capacity to form a catalytic selenol(ate). This coupling provides a very effective means of modulating oxidation and reduction. Remarkably, selenium compounds catalyze the oxidation of MT even under overall reducing conditions such as those prevailing in the cytosol. In this manner, the binding and release of zinc from zinc–thiolate co‐ordination sites is linked to redox catalysis by selenium compounds, changes in the glutathione redox state, and the availability of either a zinc donor or a zinc acceptor. The results also suggest that the pharmacological actions of selenium compounds in cancer prevention and other antiviral and anti‐inflammatory therapeutic applications, as well as unknown functions of selenium‐containing proteins, may relate to coupling between the thiol redox state and the zinc state.
Roles of homocysteine in cell metabolism
Authors: Medina Miguel Á. , Urdiales José L. , Amores‐Sánchez María I. 
Published: March 2003

Mild hyperhomocysteinemia has been suggested as a new, independent risk factor for cardiovascular disease. This fact has produced a new, increased interest in the study of homocysteine metabolism and its relation to pathogenesis. This emergent area of biomedical research is reviewed here, stressing the biochemical and metabolic basis of the pathogenicity of increased levels of homocysteine.
Philopatry, Site Fidelity and Local Kin Associations within Grey Seal Breeding Colonies
Authors: Pomeroy P. P. , Twiss S. D. , Redman P. 
Published: March 2003

Abstract Colonially breeding animals such as grey seals typically have a discrete number of breeding sites. The extent to which offspring are philopatric (return to breed at their natal site) and the prevalence of philopatry by sex of pup has fundamental consequences for the social and genetic structure within and between each colony.Grey seals born and marked by tagging and cohort brands at colonies on North Rona, Outer Hebrides since 1960 and at the Isle of May, Firth of Forth since 1981 have shown philopatry. Overall re‐sight rates of 1620 pups tagged at North Rona and 1667 pups at the Isle of May ranged from 0 to 17%. Although most evidence of philopatry relates to females, males at each colony displayed philopatry. In addition, females born at N. Rona pupped closer to their natal sites than would be expected by chance (p = 0.005), providing evidence of fine scale natal site fidelity. Females born at the Isle of May did not show the same degree of fine scale natal site fidelity, but there was considerable individual variation. The spatial scale of philopatry shown by seals differed according to the local area within each island. Fidelity of known adult females to pupping sites at both colonies was high. In addition, we found an instance of mother and daughter pupping together away from the daughter's natal site.These data: (i) provide evidence of philopatry in both sexes at each site; (ii) describe occurrences of fine scale philopatry at both sites; (iii) show that mothers and offspring occupied the same areas on the colony, suggesting the possibility of highly related groups within colonies, which would provide conditions for kin‐specific altruistic behaviours; (iv) suggest the possibility of individual or kin recognition, even though contact between mothers and offspring has been thought to cease after the 18 d lactation period.
Memory of Location and Site Recognition in the Ant Formica uralensis (Hymenoptera: Formicidae)
Authors: Salo Outi , Rosengren Rainer 
Published: March 2003

Spatial recognition cues used in site fidelity in the ant Formica uralensis Ruzsky were studied using outdoor and laboratory arenas. Ant workers visiting symmetrically spaced feeders were colour‐marked corresponding to the initial feeder visited during sampling. The effect of manipulating environmental cues on the mean ‘spatial specialization’ of the population was measured. Site recognition appears to be based on visual landmark/canopy cues. However, ants maintained some fidelity when shielded from these cues, suggesting the involvement of additional cues. When ridding our experimental device of olfactory deposits and shielding visual cues, site fidelity was lost. Idiothetic and/or geomagnetic cues are thought to provide spatial references to visual or olfactory landmarks. Altering nest position relative to the arena and changing the geomagnetic field within the arena in our study, however, did nothing to the site fidelity of visually deprived and non‐deprived foragers.We conclude that site fidelity is developed in a visually structured environment but supplemented by an olfactory backup system that is probably based on discrete home range markings rather than radial odour trails. We demonstrate furthermore that the visual component involved in site location can be stored in the memory of individual F. uralensis foragers during a 6‐month hibernation period.
Olfactory Discrimination of Individual Scents in the Subterranean Rodent Ctenomys talarum (tuco‐tuco)
Authors: Zenuto Roxana R. , Fanjul María Sol 
Published: March 2003

AbstractBiological odours that convey cues regarding individual identity can provide valuable information mediating many aspects of mammalian social relationships such us dominance hierarchies, group memberships, territorial and mating activities. The ability of the subterranean rodent, tuco‐tuco (Ctenomys talarum), to discriminate between soiled shavings, urine and faeces from different individuals was investigated using the habituation–discrimination paradigm. Discrimination by both males and females was tested using scents obtained from same‐ and opposite‐sex individuals. Each test subject was habituated for three consecutive days to odour samples from the same individual; on the fourth day a scent from a novel individual was provided. For all odour sources, animals spent significantly less time investigating the habituation scent over successive trials, indicating that animals perceived the stimulus as familiar. For all stimuli, test subjects spent more time investigating the novel odour, rather than the familiar one. Animals spent more time investigating soiled shavings than urine or faeces. Both males and females discriminated novel from familiar odours in shavings and urine regardless of the gender of the odour donors. In contrast, test animals discriminated between familiar and novel odours in feces only when the fecal donors were of different sex from subjects. Possible territorial and reproductive functions of individual scent discrimination are discussed.
Intra‐Colonial Variability in the Dance Communication in Honeybees (Apis mellifera)
Authors: Arnold Gérard , Quenet Brigitte , Papin Christian , Masson Claudine , Kirchner Wolfgang H. 
Published: March 2003

AbstractHoneybees have evolved numerous mechanisms for increasing colony‐level foraging efficiency, mainly the combined system of scout‐recruit division of labour and recruitment communication. A successful forager performs waggle dances on the surface of the comb where it interacts with nectar receivers and dance followers. A forager uses tremble dance when it experiences difficulty finding a receiver bee to unload food upon return to the hive. A bee colony containing numerous subfamilies may increase its efficiency in dance communication if dances are realized by particular groups of specialized individuals or subfamilies rather than by undifferentiated workers. In this study, we determined the subfamily frequencies of waggle and tremble dancers in a colony headed by a naturally mated queen, where the 17 subfamilies can be identified by microsatellite genetic markers. Our results demonstrate that a genetic component is associated with the dance communication in honeybees. More than half of the waggle dances and the tremble dances were performed by workers from only four subfamilies in each case.
Responses of Snow Voles, Chionomys nivalis, Towards Conspecific Cues Reflect Social Organization during Overwintering Periods
Authors: Luque‐Larena Juan J. , López Pilar , Gosálbez Joaquim 
Published: March 2003

AbstractAmong microtine rodents, reaction to chemical cues from conspecifics is assumed to reflect social and spatial relationships. Generally, strong attraction of particular odours correlates with non‐aggressive behaviour and high spatial tolerance towards odour donors, whereas weak attraction correlates with greater levels of aggression and spatial segregation. In the present study, we examined whether winter odour preferences of the snow vole Chionomys nivalis, a rock‐dwelling microtine principally found at high‐mountainous regions, differ from that of other vole species, owing to their different social organization during overwintering periods. The social structure of C. nivalis over the winter period is relatively unusual among vole species in that they become nomadic and solitary. In odour choice trials under laboratory conditions, we found that both males and females avoided zones with conspecific odours of both sexes in comparison with unscented control zones or own odours. These results are consistent with the elevated levels of intraspecific aggression and spatial isolation of C. nivalis during overwintering periods. Furthermore, scent‐elicited self‐grooming increased when their own odour was offered against conspecific cues. This, in combination with an active avoidance of conspecific odours, might functionally contribute to minimize direct confrontations between solitary individuals, thereby reducing the risks of aggressive encounters during overwintering periods.
Individual and Contextual Variation in Thomas Langur Male Loud Calls
Authors: Wich Serge A. , Koski Sonja , de Vries Han , van Schaik Carel P. 
Published: March 2003

AbstractIndividual and contextual differences in male loud calls of wild Thomas langurs (Presbytis thomasi) were studied in northern Sumatra, Indonesia. Loud calls were given in the following contexts: morning calls, vocal responses to other groups, between‐group encounter calls and alarm calls. Loud call spectrograms were analysed for a large number of variables. With discriminant analyses, 14 variables were found to be important in distinguishing individuals and contexts. Loud calls were assigned to the correct individual in 95.6% of the cases (91.8% with ‘leave‐one‐out’ validation) and to the correct context in 52.2% of the cases (39.0% with ‘leave‐one‐out’ validation). Further analyses with two‐way anovas showed significant differences in both temporal and frequency variables between individuals and contexts. Loud calls seemed to differ between the contexts in functionally meaningful ways, relating to the distance of the intended receivers and to the urgency of the message. Observation showed that females in the caller's group collected infants more often in the between‐group encounter context and in the alarm call context than in the vocal exchange context. These differential responses suggest that the monkeys also perceive the measurable differences in loud call characteristics between the various contexts.