bluuebunny/crossref_metadata_2025 huggingface dataset:
A Resource-based View of Strategic Alliances and Firm Value in the Electronic Marketplace
Authors: Park Namgyoo K. , Mezias John M. , Song Jaeyong
Published: October 2003

This study relies on the resource-based view to examine how alliances of e-commerce firms affect firm value in an emerging business sector. Using an event study method, we investigate 272 alliances of 69 e-commerce firms. Our findings show that alliances of e-commerce firms in general have a positive effect on firm value. Unlike previous studies of alliances, we find that marketing alliances generate significantly greater firm value than technology alliances. Our results also show that alliances with other e-commerce partners do not have a significantly different effect on firm value than alliances with bricks-and-mortar partners. Implications and avenues for future research are discussed.
The Fairness of Decision Rules
Authors: Conlon Donald E. , Porter Christopher O.L.H. , Parks Judi McLean
Published: October 2003

Prior work on resource allocation has generally considered only a small number of allocation rules, usually reflecting equity or equality. We use a scenario study to examine the effect of eight different allocation rules (past performance, future performance, rank, random draw, chance meetings, business need, personal need, and political reasons) on recipient reactions to the gain or loss of three different kinds of resources in an organizational setting. We find evidence that allocations based on past performance and random draw rules lead to the highest fairness perceptions and the lowest expectations that the decisions made will lead to intragroup conflict. However, fairness judgments are also influenced by a variety of other factors, such as the type of resource being allocated and whether the recipient is advantaged or disadvantaged relative to others in the workgroup (what we term the “egocentric interaction”). We discuss how our results might influence managers’ allocation decisions.
Entrepreneurs’ Decisions to Exploit Opportunities
Authors: Choi Young Rok , Shepherd Dean A.
Published: October 2003

Opportunity exploitation is a necessary step in creating a successful business in the entrepreneurial process, yet there has been little conceptual and empirical development of this issue in the literature. This study examines the decisions of entrepreneurs to begin exploiting business opportunities from a resource-based view. Our analysis of a sample of entrepreneurs whose businesses are located in incubators suggests that entrepreneurs are more likely to exploit opportunities when they perceive more knowledge of customer demand for the new product, more fully developed necessary technologies, greater managerial capability, and greater stakeholder support. Moreover, the findings of this study shed a light on a less emphasized aspect of the resource-based view: the new product’s anticipated lead time acts as an enhancing moderator in entrepreneurs’ exploitation decision policies. Implications for future research on opportunity exploitation are discussed.
Growth rate regulation of lac operon expression in Escherichia coli is cyclic AMP dependent
Authors: Kuo Jong-Tar , Chang Yu-Jen , Tseng Ching-Ping
Published: October 2003

In contrast to the ribosomal RNA gene expression increasing with growth rate, transcription of the lac operon is downregulated by cell growth rate. In continuous culture, growth rate regulation of lac promoter was independent of carbon substrate used and its location on the chromosome. Since the lac operon is activated by cyclic adenosine monophosphate (cAMP), which decreases with increasing cell growth rate, expression of plac‐lacZ reporter fusion was analyzed in cya mutant under various growth conditions. The results demonstrated that expression of plac‐lacZ in cya mutant was both lower and growth rate independent. In addition, ppGpp (guanosine tetraphosphate) was not involved in the mechanism of growth rate regulation of the lac promoter. Thus, the results of this study indicate that cAMP mediates the growth rate‐dependent regulation of lac operon expression in Escherichia coli.
T3JAM, a novel protein that specifically interacts with TRAF3 and promotes the activation of JNK1
Authors: Dadgostar Hajir , Doyle Sean E. , Shahangian Arash , Garcia Daniel E. , Cheng Genhong
Published: October 2003

Previous studies suggest that localization of tumor necrosis factor receptor (TNFR)‐associated factor (TRAF) family members is important for regulating their signal transduction. During a screen for TRAF3‐associated proteins that potentially alter TRAF3 subcellular localization and enable signal transduction, we identified a novel protein, T3JAM (TRAF3‐interacting Jun N‐terminal kinase (JNK)‐activating modulator). This protein associates specifically with TRAF3 but not other TRAF family members. Coexpression of T3JAM with TRAF3 recruits TRAF3 to the detergent‐insoluble fraction. More importantly, T3JAM and TRAF3 synergistically activate JNK but not nuclear factor (NF)‐κB. Our studies indicate that T3JAM may function as an adapter molecule that specifically regulates TRAF3‐mediated JNK activation.
Interaction of Calmodulin, a Sorting Nexin and Kinase-Associated Protein Phosphatase with the Brassica oleracea S Locus Receptor Kinase
Authors: Vanoosthuyse Vincent , Tichtinsky Gabrielle , Dumas Christian , Gaude Thierry , Cock J. Mark
Published: October 2003

Recognition of self-pollen during the self-incompatibility response in Brassica oleracea is mediated by the binding of a secreted peptide (the S locus cysteine-rich protein) to the S locus receptor kinase (SRK), a member of the plant receptor kinase (PRK) superfamily. Here, we describe the characterization of three proteins that interact with the cytosolic kinase domain of SRK. A B. oleracea homolog of Arabidopsis kinase-associated protein phosphatase was shown to interact with and dephosphorylate SRK and was itself phosphorylated by SRK. Yeast (Saccharomyces cerevisiae) two-hybrid screens identified two additional interactors, calmodulin and a sorting nexin, both of which have been implicated in receptor kinase down-regulation in animals. A calmodulin-binding site was identified in sub-domain VIa of the SRK kinase domain. The binding site is conserved and functional in several other members of the PRK family. The sorting nexin also interacted with diverse members of the PRK family, suggesting that all three of the interacting proteins described here may play a general role in signal transduction by this family of proteins.
Proteomics ofMedicago truncatulaSeed Development Establishes the Time Frame of Diverse Metabolic Processes Related to Reserve Accumulation
Authors: Gallardo Karine , Le Signor Christine , Vandekerckhove Joël , Thompson Richard D. , Burstin Judith
Published: October 2003

We utilized a proteomic approach to investigate seed development in Medicago truncatula, cv Jemalong, line J5 at specific stages of seed filling corresponding to the acquisition of germination capacity and protein deposition. One hundred twenty proteins differing in kinetics of appearance were subjected to matrix-assisted laser desorption ionization time of flight mass spectrometry. These analyses provided peptide mass fingerprint data that identified 84 of them. Some of these proteins had previously been shown to accumulate during seed development in legumes (e.g. legumins, vicilins, convicilins, and lipoxygenases), confirming the validity of M. truncatula as a model for analysis of legume seed filling. The study also revealed proteins presumably involved in cell division during embryogenesis (β-tubulin and annexin). Their abundance decreased before the accumulation of the major storage protein families, which itself occurs in a specific temporal order: vicilins (14 d after pollination [DAP]), legumins (16 DAP), and convicilins (18 DAP). Furthermore, the study showed an accumulation of enzymes of carbon metabolism (e.g. sucrose synthase, starch synthase) and of proteins involved in embryonic photosynthesis (e.g. chlorophyll a/b binding), which may play a role in providing cofactors for protein/lipid synthesis or for CO2 refixation during seed filling. Correlated with the reserve deposition phase was the accumulation of proteins associated with cell expansion (actin 7 and reversibly glycosylated polypeptide) and of components of the precursor accumulating vesicles, which give rise to a trypsin inhibitor on maturation. Finally, we revealed a differential accumulation of enzymes involved in methionine metabolism (S-adenosyl-methionine synthetase and S-adenosylhomo-cysteine hydrolase) and propose a role for these enzymes in the transition from a highly active to a quiescent state during seed development.
Zeaxanthin Deficiency Enhances the High Light Sensitivity of an Ascorbate-Deficient Mutant of Arabidopsis
Authors: Müller-Moulé Patricia , Havaux Michel , Niyogi Krishna K.
Published: October 2003

The ascorbate content of plants is usually increased in high light (HL), implying a function for ascorbate in the acclimation of plants to HL. Nevertheless, the importance of ascorbate in HL acclimation has not yet been tested directly. Here, we report on the acclimation process of an ascorbate-deficient Arabidopsis mutant to HL. The mutant vtc2 has only 10% to 30% of wild-type levels of ascorbate, and it is also slightly deficient in feedback de-excitation (qE), a photoprotective mechanism that causes the dissipation of excess light as heat. The vtc2 mutant was unable to acclimate to HL, when transferred from low light to HL. Its mature leaves bleached, and it showed an increased degree of lipid peroxidation and photoinhibition. In parallel, we tested the photosensitivity of an ascorbate-deficient xanthophyll cycle mutant, vtc2npq1, which also lacks zeaxanthin and nearly all qE. The double mutant bleached sooner and had higher degrees of lipid peroxidation and photoinhibition than the vtc2 mutant. This was in contrast to the npq1 single mutant that showed only slight deviations from the wild-type phenotype under the conditions used. These results demonstrate the antioxidant role of ascorbate in the acclimation process to HL and point to the relative importance of ascorbate in comparison with other photoprotective processes, such as specific xanthophylls or feedback de-excitation. The results also provide further support for the proposed role of zeaxanthin as an antioxidant and lipid stabilizer.
Characterization of Salt-Regulated Mannitol-1-Phosphate Dehydrogenase in the Red Alga Caloglossa continua
Authors: Iwamoto Koji , Kawanobe Hideaki , Ikawa Tomoyoshi , Shiraiwa Yoshihiro
Published: October 2003

Mannitol-1-phosphate (M1P) dehydrogenase (M1PDH; EC 1.1.1.17), an enzyme catalyzing the reduction of Fru-6-phosphate (F6P) to M1P in algal mannitol biosynthesis, was purified to homogeneity from a cell homogenate of the eulittoral red alga Caloglossa continua (Okamura) King et Puttock. The enzyme was a monomer with an apparent molecular mass of 53 kD, as determined by gel filtration and SDS-PAGE, and exhibited an pI of approximately 5.5. The substrate specificity was very high toward F6P and M1P for respective reductive and oxidative reactions. The enzyme was found to be a sulfhydryl-type, because its activity was inhibited by N-ethylmaleimide and p-hydroxymercuribenzoate, and the inhibition by p-hydroxymercuribenzoate was rescued by 2-mercaptoethanol. Some unknown factors in the extract may also have inhibited the activity, because the total activity was greatly increased through the purification procedure. The optimum pH for F6P reduction was changed from 6.0 or lower to 7.2 by the addition of 200 mm NaCl. The reduction of F6P showed strong substrate inhibition above 0.5 mm. However, K  m(F6P) of M1PDH was increased eight times by the addition of 200 mm NaCl, whereas V  max was in a similar range with the avoidance of substrate inhibition by F6P. These results indicate that the enzyme was finely and directly regulated by the salt concentration without the requirement for gene expression. M1PDH can therefore be a key enzyme for regulating mannitol biosynthesis when the alga is stressed by a salinity change.
Transcriptional Profiling of Arabidopsis Tissues Reveals the Unique Characteristics of the Pollen Transcriptome
Authors: Becker Jörg D. , Boavida Leonor C. , Carneiro Jorge , Haury Matthias , Feijó José A.
Published: October 2003

Pollen tubes are a good model for the study of cell growth and morphogenesis because of their extreme elongation without cell division. Yet, knowledge about the genetic basis of pollen germination and tube growth is still lagging behind advances in pollen physiology and biochemistry. In an effort to reduce this gap, we have developed a new method to obtain highly purified, hydrated pollen grains of Arabidopsis through flowcytometric sorting, and we used GeneChips (Affymetrix, Santa Clara, CA; representing approximately 8,200 genes) to compare the transcriptional profile of sorted pollen with those of four vegetative tissues (seedlings, leaves, roots, and siliques). We present a new graphical tool allowing genomic scale visualization of the unique transcriptional profile of pollen. The 1,584 genes expressed in pollen showed a 90% overlap with genes expressed in these vegetative tissues, whereas one-third of the genes constitutively expressed in the vegetative tissues were not expressed in pollen. Among the 469 genes enriched in pollen, 162 were selectively expressed, and most of these had not been associated previously with pollen. Their functional classification reveals several new candidate genes, mainly in the categories of signal transduction and cell wall biosynthesis and regulation. Thus, the results presented improve our knowledge of the molecular mechanisms underlying pollen germination and tube growth and provide new directions for deciphering their genetic basis. Because pollen expresses about one-third of the number of genes expressed on average in other organs, it may constitute an ideal system to study fundamental mechanisms of cell biology and, by omission, of cell division.
Sfp1 Plays a Key Role in Yeast Ribosome Biogenesis
Authors: Fingerman Ian , Nagaraj Vijayalakshmi , Norris David , Vershon Andrew K.
Published: October 2003

Sfp1, an unusual zinc finger protein, was previously identified as a gene that, when overexpressed, imparted a nuclear localization defect.
sfp1
cells have a reduced size and a slow growth phenotype. In this study we show that
SFP1
plays a role in ribosome biogenesis. An
sfp1
strain is hypersensitive to drugs that inhibit translational machinery.
sfp1
strains also have defects in global translation as well as defects in rRNA processing and 60S ribosomal subunit export. Microarray analysis has previously shown that ectopically expressed
SFP1
induces the transcription of a large subset of genes involved in ribosome biogenesis. Many of these induced genes contain conserved promoter elements (RRPE and PAC). Our results show that activation of transcription from a reporter construct containing two RRPE sites flanking a single PAC element is
SFP1
dependent. However, we have been unable to detect direct binding of the protein to these elements. This suggests that regulation of genes containing RRPEs is dependent upon Sfp1 but that Sfp1 may not directly bind to these conserved promoter elements; rather, activation may occur through an indirect mechanism.
Bacterial Catalase in the Microsporidian
Nosema locustae
: Implications for Microsporidian Metabolism and Genome Evolution
Authors: Fast Naomi M. , Law Joyce S. , Williams Bryony A. P. , Keeling Patrick J.
Published: October 2003

Microsporidia constitute a group of extremely specialized intracellular parasites that infect virtually all animals. They are highly derived, reduced fungi that lack several features typical of other eukaryotes, including canonical mitochondria, flagella, and peroxisomes. Consistent with the absence of peroxisomes in microsporidia, the recently completed genome of the microsporidian
Encephalitozoon cuniculi
lacks a gene for catalase, the major enzymatic marker for the organelle. We show, however, that the genome of the microsporidian
Nosema locustae
, in contrast to that of
E. cuniculi
, encodes a group II large-subunit catalase. Surprisingly, phylogenetic analyses indicate that the
N. locustae
catalase is not specifically related to fungal homologs, as one would expect, but is instead closely related to proteobacterial sequences. This finding indicates that the
N. locustae
catalase is derived by lateral gene transfer from a bacterium. The catalase gene is adjacent to a large region of the genome that appears to be far less compact than is typical of microsporidian genomes, a characteristic which may make this region more amenable to the insertion of foreign genes. The
N. locustae
catalase gene is expressed in spores, and the protein is detectable by Western blotting. This type of catalase is a particularly robust enzyme that has been shown to function in dormant cells, indicating that the
N. locustae
catalase may play some functional role in the spore. There is no evidence that the
N. locustae
catalase functions in a cryptic peroxisome.
Attachment of the Ubiquitin-Related Protein Urm1p to the Antioxidant Protein Ahp1p
Authors: Goehring April S. , Rivers David M. , Sprague George F.
Published: October 2003

Urm1p is a ubiquitin-related protein that serves as a posttranslational modification of other proteins. Urm1p conjugation has been implicated in the budding process and in nutrient sensing. Here, we have identified the first in vivo target for the urmylation pathway as the antioxidant protein Ahp1p. The attachment of Urm1p to Ahp1p requires the E1 for the urmylation pathway, Uba4p. Loss of the urmylation pathway components results in sensitivity to a thiol-specific oxidant, as does loss of Ahp1p, implying that urmylation has a role in an oxidative-stress response. Moreover, treatment of cells with thiol-specific oxidants affects the abundance of Ahp1p-Urm1p conjugates. These results suggest that the conjugation of Urm1p to Ahp1p could regulate the function of Ahp1p in antioxidant stress response in
Saccharomyces cerevisiae
.
Venture Survival in a Transitional Economy
Authors: Lyles Marjorie A. , Saxton Todd , Watson Kathleen
Published: October 2003

Many formerly controlled economies have undergone discontinuous transformations in their approach to markets, institutional environments, and the role of government in economic activity. We study the factors that affect venture survival in a transitional economy through a two-stage study of private ventures in Hungary. We find that ventures survive under uncertainty, even without significant government support. Industry experience, networking activities, and the strategic orientation of the firms predict survival. Contrary to our predictions, SOE experience, access to infrastructure, and differentiation strategies do not significantly differentiate survivors.
Posttranslational Modifications Required for Cell Surface Localization and Function of the Fungal Adhesin Aga1p
Authors: Huang Guohong , Zhang Mingliang , Erdman Scott E.
Published: October 2003

Adherence of fungal cells to host substrates and each other affects their access to nutrients, sexual conjugation, and survival in hosts. Adhesins are cell surface proteins that mediate these different cell adhesion interactions. In this study, we examine the in vivo functional requirements for specific posttranslational modifications to these proteins, including glycophosphatidylinositol (GPI) anchor addition and O-linked glycosylation. The processing of some fungal GPI anchors, creating links to cell wall β-1,6 glucans, is postulated to facilitate postsecretory traffic of proteins to cell wall domains conducive to their functions. By studying the yeast sexual adhesin subunit Aga1p, we found that deletion of its signal sequence for GPI addition eliminated its activity, while deletions of different internal domains had various effects on function. Substitution of the Aga1p GPI signal domain with those of other GPI-anchored proteins, a single transmembrane domain, or a cysteine capable of forming a disulfide all produced functional adhesins. A portion of the cellular pool of Aga1p was determined to be cell wall resident. Aga1p and the α-agglutinin Agα1p were shown to be under glycosylated in cells lacking the protein mannosyltransferase genes
PMT1
and
PMT2
, with phenotypes manifested only in MATα cells for single mutants but in both cell types when both genes are absent. We conclude that posttranslational modifications to Aga1p are necessary for its biogenesis and activity. Our studies also suggest that in addition to GPI-glucan linkages, other cell surface anchorage mechanisms, such as transmembrane domains or disulfides, may be employed by fungal species to localize adhesins.
Sulfonated human immunoglobulin enhances CD16‐linked CD11b expression on human neutrophils
Authors: Kimura Hirokazu , Kato Masahiko , Ikeda Miyuki , Nagai Akira , Okada Yasunori , Naito Shigeto , Oshima Shigeru , Taniguchi Koichi , Kozawa Kunihisa , Morikawa Akihiro
Published: October 2003

Intravenous human immunoglobulin therapy infrequently results in excessive inflammatory responses in vivo; these effects are not fully understood. We assessed whether sulfonated human immunoglobulin (SHIG) or polyethylene glycol‐treated human immunoglobulin (PHIG) enhanced expression of inflammatory receptors on peripheral blood neutrophils in vitro, such as αMβ2 (CD11b/CD18) and Fc gamma receptor type III (FcγRIII). CD11b and CD16 expression on neutrophils was measured by fluorescence flow cytometry. Various cytokines were assessed using a highly sensitive fluorescence microsphere system. SHIG enhanced/induced CD11b expression and partial aggregations on neutrophils, but PHIG did not. No detection of aggregation IgG was observed in SHIG and PHIG. SHIG‐induced CD11b expression was inhibited by treatment of corticosteroid (dexamethasone) and by anti‐CD16 monoclonal antibody. Concentrations of various cytokines such as interleukin (IL)‐1β, IL‐2, IL‐4, IL‐5, IL‐6, IL‐8, IL‐10, RANTES, tumor necrosis factor (TNF)‐α, and interferon (INF)‐γ in culture supernatant were not significantly changed by SHIG or PHIG. SHIG and PHIG did not enhance CD16 on neutrophils. SHIG enhanced CD16‐linked CD11b expression on neutrophils in vitro. CD11b induction was inhibited by dexamethasone and by anti‐CD16 antibody. These in vitro results suggest that aggregations and enhancement of CD11b on neutrophils by SHIG may induce excessive inflammatory responses in vivo.
Loss of hepatocyte co‐operative activity after inhibition of ganglioside GM1 synthesis and shedding
Authors: Brodsky Vsevolod , Zvezdina Natalia , Nechaeva Natalia , Novikova Tatjana , Gvasava Inessa , Fateeva Valentina , Gracheva Helena
Published: October 2003

Pretreatment of hepatocyte cultures with 1 μM d‐l‐threo‐1‐phenyl‐2‐hexadecanoylamino‐3‐pyrrolidino‐1‐propanol‐HCL (PPPP) for 24 h decreased the ganglioside GM1 content of the cells by ∼50% and that of the conditioned medium by 90%. No rhythm in the rate of protein synthesis was detected in dense cultures pretreated with PPPP, but was observed in control dense cultures. Conditioned medium from control dense cultures induced synchrony in sparse cultures, which were non‐synchronous in their own medium. In contrast, conditioned medium from dense cultures pretreated with PPPP did not synchronize sparse cultures. Since protein synthesis rhythm is a marker of cell synchronization, i.e. their co‐operative activity, then non‐oscillatory behavior means loss of cell co‐operation. The protein synthesis rhythm was restored 24 h after hepatocytes were transferred to PPPP‐free medium. Restoration was more rapid when 0.9 μM gangliosides (standard mixture from bovine brain) were added to the medium just after the withdrawal of PPPP. These novel results concerning the loss of rhythm of protein synthesis in low GM1 ganglioside medium support the conclusion that ganglioside is implicated in the regulation of cell co‐operative activity.
Pioglitazone reduces monocyte adhesion to vascular endothelium under flow by modulating RhoA GTPase and focal adhesion kinase
Authors: Toriumi Yasutoshi , Hiraoka Megumi , Watanabe Mamoru , Yoshida Masayuki
Published: October 2003

Thiazolidinediones (TZDs), potent peroxisome proliferator‐activated receptor γ ligands, have been shown to improve endothelial function in vascular diseases. We investigated the effects of pioglitazone, a TZD, on monocyte–endothelial interaction under flow and found that pretreatment (20 μmol/l, 48 h) significantly reduced U937 adhesion to human umbilical vein endothelial cells. Integrin expression was not altered, however, the activation of RhoA GTPase was significantly reduced after treatment. Further, pioglitazone treatment significantly reduced phosphorylation of focal adhesion kinase (FAK) at 925Y, but not at 397Y, suggesting a specific role in FAK‐dependent signaling. These results indicate a novel anti‐inflammatory role for this compound.
Anhydrobiosis without trehalose in bdelloid rotifers
Authors: Lapinski Jens , Tunnacliffe Alan
Published: October 2003

Eukaryotes able to withstand desiccation enter a state of suspended animation known as anhydrobiosis, which is thought to require accumulation of the non‐reducing disaccharides trehalose (animals, fungi) and sucrose (plants), acting as water replacement molecules and vitrifying agents. We now show that clonal populations of bdelloid rotifers Philodina roseola and Adineta vaga exhibit excellent desiccation tolerance, but that trehalose and other disaccharides are absent from carbohydrate extracts of dried animals. Furthermore, trehalose synthase genes (tps) were not found in rotifer genomes. This first observation of animal anhydrobiosis without trehalose challenges our current understanding of the phenomenon and calls for a re‐evaluation of existing models.
MALS is a binding partner of IRSp53 at cell–cell contacts
Authors: Hori Kei , Konno Daijiro , Maruoka Hisato , Sobue Kenji
Published: October 2003

Insulin receptor substrate p53 (IRSp53) is a key player in cytoskeletal dynamics, interacting with the actin modulators WAVE2 and Mena. Here, we identified a PDZ protein, MALS, as an IRSp53‐interacting protein using a yeast two‐hybrid screen. A pull‐down assay showed that IRSp53 and MALS interact through the PDZ domain of MALS and the C‐terminal PDZ‐binding sequence of IRSp53. Their interaction in MDCK cells was also demonstrated by co‐immunoprecipitation. Immunocytochemistry showed the colocalization of IRSp53 and MALS at cell–cell contacts. Cytochalasin D induced the redistribution of both proteins to the cytosol. Thus, MALS is a partner of IRSp53 anchoring the actin‐based membrane cytoskeleton at cell–cell contacts.
Plant PIP2‐dependent phospholipase D activity is regulated by phosphorylation
Authors: Novotná Zuzana , Linek Jan , Hynek Radovan , Martinec Jan , Potocký Martin , Valentová Olga
Published: October 2003

Phospholipase D (PLD) forms the major family of phospholipases that was first discovered and cloned in plants. In this report we have shown, for the first time, that C2 phosphatidylinositol‐4,5‐bisphosphate (PIP2)‐dependent PLD(s) from 5 day hypocotyls of Brassica oleracea associated with plasma membrane is covalently modified‐phosphorylated. Pre‐incubation of the plasma membrane fraction with acid phosphatase resulted in concentration‐dependent inhibition of PIP2‐dependent PLD activity. Using matrix‐assisted laser desorption/ionization time of flight mass spectrometry of tryptic in‐gel digests, the BoPLDγ1,2 isoform was identified. Comparing the spectra of the proteins obtained from the plasma membrane fractions treated and non‐treated with acid phosphatase, three peptides differing in the mass of the phosphate group (80 Da) were revealed: TMQMMYQTIYK, EVADGTVSVYNSPR and KASKSRGLGK which possess five potential Ser/Thr phosphorylation sites. Our findings suggest that a phosphorylation/dephosphorylation mechanism may be involved in the regulation of plant PIP2‐dependent PLDγ activity.
Mechanics of coupling proton movements to c‐ring rotation in ATP synthase
Authors: Fillingame Robert H , Angevine Christine M , Dmitriev Oleg Y
Published: October 2003

F1F0 ATP synthases generate ATP by a rotary catalytic mechanism in which H+ transport is coupled to rotation of an oligomeric ring of c subunits extending through the membrane. Protons bind to and then are released from the aspartyl‐61 residue of subunit c at the center of the membrane. Subunit a of the F0 sector is thought to provide proton access channels to and from aspartyl‐61. Here, we summarize new information on the structural organization of Escherichia coli subunit a and the mapping of aqueous‐accessible residues in the second, fourth and fifth transmembrane helices (TMHs). Aqueous‐accessible regions of these helices extend to both the cytoplasmic and periplasmic surface. We propose that aTMH4 rotates to alternately expose the periplasmic or cytoplasmic half‐channels to aspartyl‐61 of subunit c during the proton transport cycle. The concerted rotation of interacting helices in subunit a and subunit c is proposed to be the mechanical force driving rotation of the c‐rotor, using a mechanism akin to meshed gears.
A large-mesh salmon trap: a way of mitigating seal impact on a coastal fishery
Authors: Lunneryd Sven Gunnar , Fjälling Arne , Westerberg Håkan
Published: October 2003

A new design for a salmon trap aimed at minimizing damage to catch and gear caused by grey seals was tested. The traditional trap design used in the northern Baltic permits an efficient hunting strategy by seals, whereby chased fish entangle themselves in the side panels and can then easily be taken, with associated damage to the net. The side panels of the test trap (excluding the fish chamber) are made of large-mesh (400 mm) netting compared to ≤200 mm in traditional traps. This should allow seal-chased and panicking salmon to pass through, while less stressed individuals should still be guided efficiently towards the fish chamber. Trials with the two trap types were performed at the mouth of the river Indal (northern Sweden) in a comparative test programme. Catches of salmon and trout in the test trap were larger than in the standard trap. We estimated that 65% of the potential catch was lost in the standard trap owing to seal predation, while escape rate through the large meshes in the test trap was 52%. The standard trap had a total of 269 holes owing to seal damage, while only six holes were found in the test trap. Seal activity in and around the standard trap was up to 16 times higher compared with the test trap and decreased considerably during the following year when only large-meshed traps were used in the area. We suggest that seals are difficult to deter from fishing gear as long as they get a reward in terms of food and propose that a strategy that deprives seals of a reward will make the gear uninteresting to them and may have long-term mitigation effects.
Group A Streptococcus and Streptococcal Toxic Shock Syndrome: A Postpartum Case Report
Authors: Golden Sara
Published: October 2003

Streptococcal toxic shock syndrome from group A streptococcal disease is rare in the postpartum period, yet it is associated with high morbidity and mortality. Early diagnosis and treatment can lessen complications. Midwives can improve provision of postpartum care by being adequately educated about signs and symptoms of this disease, thereby enhancing their ability to recognize it and obtain the appropriate referral or collaborative medical care. A clinical presentation of postpartum streptococcal toxic shock syndrome, including provider follow‐up, is presented.
Isolation of a Gene Encoding a Copper Chaperone for the Copper/Zinc Superoxide Dismutase and Characterization of Its Promoter in Potato
Authors: Trindade Luisa M. , Horvath Beatrix M. , Bergervoet Marjan J.E. , Visser Richard G.F.
Published: October 2003

Gene expression during the potato (Solanum tuberosum) tuber lifecycle was monitored by cDNA-amplified fragment-length polymorphism, and several differentially expressed transcript-derived fragments were isolated. One fragment, named TDFL431, showed high homology to a copper (Cu) chaperone for Cu/zinc superoxide dismutase (CCS). The Ccs protein is responsible for the delivery of Cu to the Cu/zinc superoxide dismutase enzyme. The potato CCS (StCCS) full-length gene was isolated, and its sequence was compared with CCSs from other species. The promoter region of this gene was isolated, fused to the firefly luciferase coding sequence, and used for transformation of potato plants. The highest level of StCCS-luciferase expression was detected in the cortex of stem (like) tissues, such as stem nodes, stolons, and tubers; lower levels were detected in roots and flowers. The StCCS promoter contains regions highly homologous to several plant cis-acting elements. Three of them are related to auxin response, whereas four others are related to response to various stresses. Induction of the StCCS promoter was analyzed on 18 media, differing in hormone, sugar, and Cu content. StCCS expression was induced by auxin, gibberellins (GA4 + 7), fructose, sucrose, and glucose and was inhibited by relatively high concentrations of Cu.
Candida albicansResponse Regulator GeneSSK1Regulates a Subset of Genes Whose Functions Are Associated with Cell Wall Biosynthesis and Adaptation to Oxidative Stress
Authors: Chauhan Neeraj , Inglis Diane , Roman Elvira , Pla Jesus , Li Dongmei , Calera Jose A. , Calderone Richard
Published: October 2003

Ssk1p ofCandida albicansis a putative response regulator protein of the Hog1 two-component signal transduction system. InSaccharomyces cerevisiae, the phosphorylation state of Ssk1p determines whether genes that promote the adaptation of cells to osmotic stress are activated. We have previously shown thatC. albicans SSK1does not complement thessk1mutant ofS. cerevisiaeand that thessk1mutant ofC. albicansis not sensitive to sorbitol. In this study, we show that theC. albicans ssk1mutant is sensitive to several oxidants, including hydrogen peroxide,t-butyl hydroperoxide, menadione, and potassium superoxide when each is incorporated in yeast extract-peptone-dextrose (YPD) agar medium. We used DNA microarrays to identify genes whose regulation is affected by thessk1mutation. RNA from mutant cells (strain CSSK21) grown in YPD medium for 3 h at 30°C was reverse transcribed and then compared with similarly prepared RNA from wild-type cells (CAF2). We observed seven genes from mutant cells that were consistently up regulated (three-fold or greater compared to CAF2). InS. cerevisiae, three (AHP1,HSP12, andPYC2) of the seven genes that were up regulated provide cells with an adaptation function in response to oxidative stress; another gene (GPH1) is regulated under stress conditions by Hog1p. Three other genes that are up regulated encode a cell surface protein (FLO1), a mannosyl transferase (MNN4-4), and a putative two-component histidine kinase (CHK1) that regulates cell wall biosynthesis inC. albicans. Of the down-regulated genes,ALS1is a known cell adhesin inC. albicans. Verification of the microarray data was obtained by reverse transcription-PCR forHSP12,AHP1,CHK1,PYC2,GPH1,ALS1,MNN4-4, andFLO1. To further determine the function of Ssk1p in the Hog1p signal transduction pathway inC. albicans, we used Western blot analysis to measure phosphorylation of Hog1p in thessk1mutant ofC. albicanswhen grown under either osmotic or oxidative stress. We observed that Hog1p was phosphorylated in thessk1mutant ofC. albicanswhen grown in a hyperosmotic medium but was not phosphorylated in thessk1mutant when the latter was grown in the presence of hydrogen peroxide. These data indicate thatC. albicansutilizes the Ssk1p response regulator protein to adapt cells to oxidative stress, while its role in the adaptation to osmotic stress is less certain. Further,SSK1appears to have a regulatory function in some aspects of cell wall biosynthesis. Thus, the functions ofC. albicans SSK1differ from those ofS. cerevisiae SSK1.
Role of Second-Largest RNA Polymerase I Subunit Zn-Binding Domain in Enzyme Assembly
Authors: Naryshkina Tatyana , Bruning Adrian , Gadal Olivier , Severinov Konstantin
Published: October 2003

The second-largest subunits of eukaryal RNA polymerases are similar to the β subunits of prokaryal RNA polymerases throughout much of their lengths. The second-largest subunits from eukaryal RNA polymerases contain a four-cysteine Zn-binding domain at their C termini. The domain is also present in archaeal homologs but is absent from prokaryal homologs. Here, we investigated the role of the C-terminal Zn-binding domain of Rpa135, the second-largest subunit of yeast RNA polymerase I. Analysis of nonfunctional Rpa135 mutants indicated that the Zn-binding domain is required for recruitment of the largest subunit, Rpa190, into the RNA polymerase I complex. Curiously, the essential function of the Rpa135 Zn-binding domain is not related to Zn
2+
binding per se, since replacement of only one of the four cysteine residues with alanine led to the loss of Rpa135 function. Even more strikingly, replacement of all four cysteines with alanines resulted in functional Rpa135.
EngineeredControl of Cell Morphology In Vivo Reveals Distinct Roles for Yeast andFilamentous Forms of
Candida albicans
duringInfection
Authors: Saville Stephen P. , Lazzell Anna L. , Monteagudo Carlos , Lopez-Ribot Jose L.
Published: October 2003

It
is widely assumed that the ability of
Candida albicans
to
switch between different morphologies is required for pathogenesis.
However, most virulence studies have used mutants that are permanently
locked into either the yeast or filamentous forms which are avirulent
but unsuitable for discerning the role of morphogenetic conversions at
the various stages of the infectious process. We have constructed a
strain in which this developmental transition can be externally
modulated both in vitro and in vivo. This was achieved by placing one
copy of the
NRG1
gene (a negative regulator of filamentation)
under the control of a tetracycline-regulatable promoter. This modified
strain was then tested in an animal model of hematogenously
disseminated candidiasis. Mice injected with this strain under
conditions permitting hyphal development succumbed to the infection,
whereas all of the animals injected under conditions that inhibited
this transition survived. Importantly, fungal burdens were almost
identical in both sets of animals, indicating that, whereas filament
formation appears to be required for the mortality resulting from a
deep-seated infection, yeast cells play an important role early in the
infectious process by extravasating and disseminating to the target
organs. Moreover, these infecting
Candida
yeast cells still
retained their pathogenic potential, as demonstrated by allowing this
developmental transition to occur at various time points postinfection.
We demonstrate here the importance of morphogenetic conversions in
C. albicans
pathogenesis. This engineered strain should
provide a useful tool in unraveling the individual contributions of the
yeast and filamentous forms at various stages of the infectious
process.
Chitin Synthesis in
Saccharomyces cerevisiae
in Response to Supplementation of Growth Medium withGlucosamine and Cell WallStress
Authors: Bulik Dorota A. , Olczak Mariusz , Lucero Hector A. , Osmond Barbara C. , Robbins Phillips W. , Specht Charles A.
Published: October 2003

In
Saccharomyces cerevisiae
most chitin is synthesized by Chs3p,
which deposits chitin in the lateral cell wall and in the bud-neck
region during cell division. We have recently found that addition of
glucosamine (GlcN) to the growth medium leads to a three- to fourfold
increase in cell wall chitin levels. We compared this result to the
increases in cellular chitin levels associated with cell wall stress
and with treatment of yeast with mating pheromone. Since all three
phenomena lead to increases in precursors of chitin, we hypothesized
that chitin synthesis is at least in part directly regulated by the
size of this pool. This hypothesis was strengthened by our finding that
addition of GlcN to the growth medium causes a rapid increase in chitin
synthesis without any pronounced change in the expression of more than
6,000 genes monitored with Affymetrix gene expression chips. In other
studies we found that the specific activity of Chs3p is higher in the
total membrane fractions from cells grown in GlcN and from mutants with
weakened cell walls. Sucrose gradient analysis shows that Chs3p is
present in an inactive form in what may be Golgi compartments but as an
active enzyme in other intracellular membrane-bound vesicles, as well
as in the plasma membrane. We conclude that Chs3p-dependent chitin
synthesis in
S. cerevisiae
is regulated both by the levels of
intermediates of the UDP-GlcNAc biosynthetic pathway and by an increase
in the activity of the enzyme in the plasma
membrane.
A
Phytophthora infestans
G-Protein β Subunit Is Involved in Sporangium Formation
Authors: Latijnhouwers Maita , Govers Francine
Published: October 2003

The heterotrimeric G-protein pathway regulates cellular responses to a wide range of extracellular signals in virtually all eukaryotes. It also controls various developmental processes in the oomycete plant pathogen
Phytophthora infestans
, as was concluded from previous studies on the role of the G-protein α-subunit PiGPA1 in this organism. The expression of the
P. infestans
G-protein β-subunit gene
Pigpb1
was induced in nutrient-starved mycelium before the onset of sporangium formation. The gene was hardly expressed in mycelium incubated in rich growth medium. The introduction of additional copies of
Pigpb1
into the genome led to silencing of the gene and resulted in transformants deficient in PiGPB1. These
Pigpb1
-silenced mutants formed very few asexual spores (sporangia) when cultured in rye sucrose medium and produced a denser mat of aerial mycelium than the wild type. Partially
Pigpb1
-silenced mutants showed intermediate phenotypes with regard to sporulation, and a relatively large number of their sporangia were malformed. The results show that PiGPB1 is important for vegetative growth and sporulation and, therefore, for the pathogenicity of this organism.
A novel feature of microsatellites in plants: a distribution gradient along the direction of transcription
Authors: Fujimori Shigeo , Washio Takanori , Higo Kenichi , Ohtomo Yasuhiro , Murakami Kazuo , Matsubara Kenichi , Kawai Jun , Carninci Piero , Hayashizaki Yoshihide , Kikuchi Shoshi , Tomita Masaru
Published: October 2003

A computer‐based analysis was conducted to assess the characteristics of microsatellites in transcribed regions of rice and Arabidopsis. In addition, two mammals were simultaneously analyzed for a comparative analysis. Our analyses confirmed a novel plant‐specific feature in which there is a gradient in microsatellite density along the direction of transcription. It was also confirmed that pyrimidine‐rich microsatellites are found intensively near the transcription start sites, specifically in the two plants, but not in the mammals. Our results suggest that microsatellites located at high frequency in the 5′‐flanking regions of plant genes can potentially act as factors in regulating gene expression.
Motif CXCC in nitrile hydratase activator is critical for NHase biogenesis in vivo
Authors: Lu Jun , Zheng Yujuan , Yamagishi Hiromi , Odaka Masafumi , Tsujimura Masanari , Maeda Mizuo , Endo Isao
Published: October 2003

Nitrile hydratase (NHase) activator from Rhodococcus sp. N‐771 is required for NHase functional expression. The motif 73CXCC76 in the NHase activator sequence was here revealed to be vital for its function by site‐directed mutagenesis. All three substitutions of the cysteines by serines resulted in a much lower level of expression of active NHase. Furthermore, interaction between NHase activator and NHase was detected and the critical role of NHase activator was not exhibited in the cysteine oxidization process of NHase. These findings suggest NHase activator mainly participates in iron trafficking in NHase biogenesis as an iron type metallochaperone.
The oxidant‐responsive diaphorase of Rhodobacter capsulatus is a ferredoxin (flavodoxin)‐NADP(H) reductase
Authors: Bittel Cristian , Tabares Leandro C. , Armesto Martín , Carrillo Néstor , Cortez Néstor
Published: October 2003

Challenge of Rhodobacter capsulatus cells with the superoxide propagator methyl viologen resulted in the induction of a diaphorase activity identified as a member of the ferredoxin (flavodoxin)‐(reduced) nicotinamide adenine dinucleotide phosphate (NADP(H)) reductase (FPR) family by N‐terminal sequencing. The gene coding for Rhodobacter FPR was cloned and expressed in Escherichia coli. Both native and recombinant forms of the enzyme were purified to homogeneity rendering monomeric products of ∼30 kDa with essentially the same spectroscopic and kinetic properties. They were able to bind and reduce Rhodobacter flavodoxin (NifF) and to mediate typical FPR activities such as the NADPH‐driven diaphorase and cytochrome c reductase.
Osgstu3 and osgtu4, encoding tau class glutathione S‐transferases, are heavy metal‐ and hypoxic stress‐induced and differentially salt stress‐responsive in rice roots1
Authors: Moons Ann
Published: October 2003

Glutathione S‐transferases (GSTs) have poorly understood roles in plant responses to environmental stresses. A polyethylene glycol (PEG)‐induced tau class GST was identified in rice roots by protein microsequencing. PEG and the heavy metals Cd (20 μM), Zn (30 μM), Co and Ni rapidly and markedly induced osgstu4 and osgstu3 in rice seedling roots. Osgstu4 and osgstu3 were also induced in roots by hypoxic stress but not by cold nor heat shock. Salt stress and abscisic acid (ABA) rapidly induced osgstu3 in rice roots, whereas osgstu4 exhibited a late salt stress and no ABA response. Salicylic acid, jasmonic acid and the auxin α‐naphthalene acetic acid triggered osgstu4 and osgstu3 expression. Osgstu4 and osgstu3 were rapidly and markedly induced by the antioxidant dithiothreitol and the strong oxidant hydrogen peroxide, which suggested that redox perturbations and reactive oxygen species are involved in their stress response regulations.
Multidrug resistance ABC transporters
Authors: Chang Geoffrey
Published: October 2003

Clinical multidrug resistance is caused by a group of integral membrane proteins that transport hydrophobic drugs and lipids across the cell membrane. One class of these permeases, known as multidrug resistance ATP binding cassette (ABC) transporters, translocate these molecules by coupling drug/lipid efflux with energy derived from the hydrolysis of ATP. In this review, we examine both the structures and conformational changes of multidrug resistance ABC transporters. Together with the available biochemical and structural evidence, we propose a general mechanism for hydrophobic substrate transport coupled to ATP hydrolysis.
Identification of genes involved in growth inhibition of breast cancer cells transduced with estrogen receptor
Authors: Licznar Anne , Caporali Simona , Lucas Annick , Weisz Alessandro , Vignon Françoise , Lazennec Gwendal
Published: October 2003

Estrogen receptor α (ERα)‐negative breast cancer cells display an aggressive phenotype. We previously showed that adenoviral expression of ERα in ER‐negative breast cancer cells leads to an estrogen‐dependent down‐regulation of the proliferation, which could be of interest to control the growth of such cells. In this study, we observed an increase in protein levels of p21 and p27 cyclin‐dependent kinase inhibitors, whereas pRb phosphorylation is strongly decreased. Flow cytometry experiments showed a slower transit of cells in G1 (hormone‐independent), a hormone‐induced accelerated transit through S phase and a possible arrest in G2/M phase. In addition, ERα‐expressing cells were undergoing apoptosis. By using cDNA macroarrays, we identified a novel collection of genes regulated by liganded ERα potentially regulating cell cycle, apoptosis, cell signalling, stress response and DNA repair.