bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in molecular species of triacylglycerols in developing cotton seeds under salt stress
Authors: Smaoui A. , Chérif A.
Published: January 2005

Cotton plants (Gossypium hirsutum L. cv. S4) were grown and irrigated with increasing salt concentrations: 0, 50, 100 and 150 mM NaCl. Lipids from developing seeds, at stages of 3, 4, 5 and 6 weeks after anthesis, were analysed. High salt dose (150 mM NaCl) affected triacylglycerol levels drastically at the end of ripening. HPLC analysis of triacylglycerols in control seeds showed ten molecular species. Palmitodilinolein (PLL) is the major fraction, representing about 25% of total triacylglycerols. The levels of trilinolein (LLL), palmitolinoleo-olein (PLO) and oleodilinolein (OLL) molecules varied between 13 and 16% of the total. The other molecular species: triolein (OOO), dioleopalmitin (POO) and dipalmitoolein (POP) are minor and do not exceed 5%. Moreover, the composition of triacylglycerol molecular species was almost constant during developing stages of control seeds. However, amounts of triacylglycerol species LLL, OLL and palmitodilinolein (PLL), as expressed on a drymatter basis (mg/g), decreased severely under the highest NaCl concentration, while contents of triacylglycerol species OOO, POO, POP were unchanged. These findings confirm our previous results, which indicated that the amount of linoleic acid in cotton seeds was reduced by salt stress and that the amount of oleic acid remained unchanged.
Changes in plasma-membrane lipid composition: a strategy for acclimation to copper stress
Authors: Berglund A. H. , Quartacci M. F. , Liljenberg C.
Published: January 2005

Wheat seedlings were grown hydroponically in the presence of 50 μM Cu2+. The copper stress resulted in plasma-membrane (PM) changes of the root cells as altered lipid composition, a decreased phosphatidylcholine (PC)/phosphatidylethanolamine (PE) ratio from 0.7 to 0.3, a decreased fatty acyl unsaturation and a decrease in the lipid/protein ratio. Membrane vesicles made from total lipid extracts of isolated PMs of wheat grown under copper excess showed a remarkably low permeability to polar molecules like glucose, as compared with the control, and no difference in proton permeability. Permeability studies of vesicles of plasma-membrane lipids, which were selectively modified by addition of specific lipids such as PC and PE, were also performed. The results are discussed with emphasis on the role of the increased PE proportion.
Effect of cadmium on lipid composition of pepper
Authors: Jemal F. , Zarrouk M. , Ghorbal M. H.
Published: January 2005

Seedlings (2 weeks old) of pepper (Capsicum annum) were grown in nutrient solution with added CdCl2 (10 or 50μM) for 7 days. In Cd-treated plants, changes in acyl lipids and fatty acid composition were investigated. Cd particularly lowered the amount of monogalactosyldiacylglycerol (MGDG) and enhanced accumulation of phospholipids [phosphatidylcholine (PC), phosphatidylethanolamine and phosphatidylglycerol] in leaves. In contrast, content of PC and galactolipids (MGDG and digalactosyldiacylglycerol) decreased in roots. Fatty acid composition of leaves was also changed by Cd addition to external medium, but no important changes occurred in roots. Levels of leaf polyunsaturated fatty acids, especially 18:3 and 16:3, were reduced. Lipid and fatty acid composition changes in roots are discussed in relation to Cd tolerance in pepper.
Effect of copper and lead on lipid metabolism in bryophytes and lichens
Authors: Guschina I. A. , Harwood J. L.
Published: January 2005

Bryophytes and lichens have a widespread occurrence and can survive under extreme environmental conditions, such as drought, low temperatures, continuous light or prolonged darkness. It has been shown that lipid metabolism is sensitive to both metal response and metal resistance mechanisms in many organisms, including yeast, Silene cucubalus and in the marine brown algae Fucus spp. and Ascophyllum nodosum. In the present study, the effects of lead and copper on lipid metabolism have been studied in two moss species, Rhytidiadelphus squarrosus and Dicranum scoparium and also in the lichen Peltigera horizontalis with a cyanobacterial Nostoc photobiont.
Environmental effects on acidic lipids of thylakoid membranes
Authors: Sato N. , Hagio M. , Wada H. , Tsuzuki M.
Published: January 2005

The contents of the chloroplast acidic lipids, SQDG (sulphoquinovosyldiacylglycerol) and PG (phosphatidylglycerol), were reduced in the cells of Chlamydomonas reinhartdtii with exposure to sulphur- or phosphorus-source limitation, respectively. The decrease in the content of one acidic lipid was accompanied by an increase in the content of the other acidic lipid, which resulted in the maintenance of a certain level of total acidic lipids of chloroplast membranes. On the other hand, the content of each acidic lipid was little affected by temperature stresses during cell growth.
Field assessment of plant derivative compounds for managing fungal soybean diseases
Authors: Brooker N. L. , Long J. H. , Stephan S. M.
Published: January 2005

Natural plant-derived compounds are currently being explored as alternatives for pest control in sustainable agriculture. This study explored the use of two compounds, sesamol and carbenoxolone, in the management of the fungal soybean disease charcoal rot (Macrophomina phaseolina). Previous studies have determined that sesamol and carbenoxolone compounds significantly inhibited fungal pathogen growth and plant disease in vitro. In order to assess the field efficacy of these compounds for fungal disease control, 2 years of field testing of these compounds have been conducted in southeast Kansas. Field treatments of the compounds sesamol and carbenoxolone at three concentrations, 0,500 and 1000 μg/ml, were applied foliarly at four distinct plant developmental stages. Treatments were applied to plots in random triplicate array and the experiment was repeated during the 1998 and 1999 growing seasons. Disease assessments were based on visual disease ratings, plant mortality and soybean yield analysis. Data were recorded weekly for each treatment plot and statistically analysed using analysis of variance. Results indicate that sesamol and carbenoxolone treatments significantly decreased disease symptoms (11–12%) and plant mortality (24–28%) while significantly increasing soybean yields (18–38%). These results support that plant-derived compounds can have a significant impact on soybean disease management and yield under field conditions.
Sulpholipid reflects plant resistance to stress-factor action
Authors: Taran N. , Okanenko A. , Musienko N.
Published: January 2005

The results of studying the behaviour of sulphoquinovosyldiacylglycerol (SQDG) during environmental-factor action are discussed. Low-temperature action caused SQDG accumulation in 1-year-old shoot bark of resistant apple varieties, and was especially striking in the Siberia apple, a variety of extreme hardiness. Another unfavourable factor, high temperature, induced SQDG accumulation in leaves and chloroplasts of drought-resistant plants while in sensitive plants a decrease in its content took place. Water deficit caused the same effect. SQDG increase was also observed in field experiments with artificial irrigation in the drought region of Ukraine, at the stages of stooling and milk ripeness. Besides, SQDG accumulation was observed in wheat plants infected by Puccinia graminis and kidney bean plants infected by tobacco mosaic and potato x viruses. But lead supplied at various concentrations caused an SQDG decrease in wheat seedling leaves and roots. The reasons for these phenomena seemed to be mainly the stabilization of the photosynthetic processes, particularly ATP synthesis and light-harvesting complex II functioning, but signal function also cannot be excluded.
Genetic modification of cotton seed oil using inverted-repeat gene-silencing techniques
Authors: Liu Q. , Singh S. , Green A.
Published: January 2005

Inverted-repeat-based gene constructs targeted against two key cotton seed-specific fatty acid desaturase genes, ghSAD-1 encoding stearoylacyl carrier protein Δ9-desaturase and ghFAD2-1 encoding microsomal ω-6 desaturase, were transformed into cotton. The expression of ghSAD-1 and ghFAD2-1 in the inverted-repeat orientation resulted in increased levels of stearic and oleic acids, respectively. Interestingly, the content of palmitic acid in both high-stearic and high-oleic lines was substantially reduced. These materials offer the promise of developing cotton seed oil products with greatly improved nutritional appeal to consumers.
Utility of the Arabidopsis FAEI and yeast SLCI-I genes for improvements in erucic acid and oil content in rapeseed
Authors: Katavic V. , Friesen W. , Barton D. L. , Gossen K. K. , Giblin E. M. , Luciw T. , An J. , Zou J. , MacKenzie S. L. , Keller W. A. , Males D. , Taylor D. C.
Published: January 2005

High-erucic acid (HEA) Brassica napus cultivars are regaining interest in industrial contexts. Erucic acid and its derivatives are important renewable raw materials utilized in the manufacture of plastic films, in the synthesis of Nylon 13,13, and in the lubricant and emollient industries. Theoretically, the highest level of erucic acid that can be achieved by means of classical breeding is 66 mol%; however, using new approaches on the basis of genetic engineering, it might be possible to develop a B. napus cultivar containing levels of erucic acid significantly above 66 mol% (> 80 mol%). In an attempt to increase the amounts of very-long-chain fatty acids (VLCFAs), and erucic acid in particular, in Canadian HEA B. napus cultivars, we have focused on two targets using a transgenic approach. We examined both the role/function of the Arabidopsis thaliana FAE1 (fatty acid elongase) gene by expressing it under the control of the seed-specific napin promoter in B. napus germplasm with analysis of the changes in VLCFA content in the seed oil of transgenic lines, and the performance of the yeast SLC1-1 (sphingolipid compensation mutant) in B. napus cv. Hero transgenic progeny in the field. Here, we report analyses of the contents of 22:1, total VLCFA and oil in the seed oil, as well as seed yield of the field-grown FAE1 and SLC1-1 B. napus cv. Hero progeny.
Inhibition of polyunsaturated fatty acid accumulation in plants expressing a fatty acid epoxygenase
Authors: Singh S. , Thomaeus S. , Lee M. , Green A. , Stymne S.
Published: January 2005

Earlier, we described the isolation of a Crepis palaestina cDNA (Cpal2) which encoded a Δ12-epoxygenase that could catalyse the synthesis of 12,13-epoxy-cis-9-octadecenoic acid (18:1E) from linoleic acid (18:2). When the Cpal2 gene was expressed under the control of a seed-specific promoter in Arabidopsis plants were able to accumulate small amounts 18:1E and 12,13-epoxy-cis-9,15-octadec-2-enoic acid in their seed lipids. In this report we give results obtained from a detailed analysis of transgenic Arabidopsis plants containing the Cpal2 gene. The seeds from these plants accumulate varying levels of 18:1E, but show a marked increase in 18:1 and equivalent decrease in 18:2 and 18:3. We further observed that the co-expression of a C. palaestina Δ12-desaturase in Arabidopsis appears to return the relative proportions of the C18 seed fatty acids to normal levels and results in a 2-fold increase in total epoxy fatty acids.
Biosynthesis of fatty acids in the docosahexaenoic acid-producing bacterium Moritella marina strain MP-I
Authors: Morita N. , Tanaka M. , Okuyama H.
Published: January 2005

We have isolated the fatty acid biosynthetic (fab) gene cluster taking part in the synthesis of middle-chain fatty acids and a genomic segment which was homologous with the eicosapentaenoic acid-biosynthetic gene cluster from the docosahexaenoic acid (DHA)-producing bacterium Moritella marina strain MP-1. This segment was presumed to include the DHA-biosynthetic gene cluster of M. marina strain MP-1. When M. marina strain MP-1 was cultured in medium containing cerulenin, a fatty acid synthesis inhibitor, decreases in levels of middle-chain fatty acids and remarkable increases in levels of DHA were observed. These results suggest that the synthesis of middle-chain fatty acids works independently of the synthesis of DHA.
Biochemical aspects of castor oil biosynthesis
Authors: McKeon T. A. , Chen G. Q. , Lin J.-T.
Published: January 2005

Castor oil is 90% ricinoleate (12-hydroxy-oleate) and has numerous industrial uses. Components of castor bean (Ricinus communis L.) pose serious problems to processors. We are evaluating two complementary approaches to providing a safe source of castor oil.
Papaya (Carica papaya) lipase with some distinct acyl and alkyl specificities as compared with microbial lipases
Authors: Gandhi N. N. , Mukherjee K. D.
Published: January 2005

Lipase from papaya (Carica papaya) latex (CPL), Candida antarctica lipase B (Novozym 435, NOV) and Rhizomucor miehei lipase (Lipozyme IM 20, LIP) were used as biocatalysts for the esterification of caprylic acid with straight-chain saturated C4-C18 alcohols and unsaturated C18 alcohols, such as cis-9-octadecenyl (oleyl, C18:1, n-9), cis-6-octadecenyl (petroselinyl, C18:1, n-12), cis-9, cis-12-octadecadienyl (linoleyl, C18:2, n-6), all-cis-9,12,15-octadecatrienyl (α-linolenyl, C18:3, n-3) and all-cis-6,9,12-octadecatrienyl (γ-linolenyl, C18:3, n-6) alcohols. With CPL, highest activity was found in the esterification of octanol and decanol, whereas both NOV and LIP showed a broad chain-length-specificity for the alcohols. CPL, as opposed to the microbial lipases, strongly discriminated against all the saturated long-chain (> C12 and unsaturated C18 alcohols.
Lipase-catalysed production of biodiesel fuel from some Nigerian lauric oils
Authors: Abigor R. D. , Uadia P. O. , Foglia T. A. , Haas M. J. , Jones K. C. , Okpefa E. , Obibuzor J. U. , Bafor M. E.
Published: January 2005

Fatty acids esters were produced from two Nigerian lauric oils, palm kernel oil and coconut oil, by transesterification of the oils with different alcohols using PS30 lipase as a catalyst. In the conversion of palm kernel oil to alkyl esters (biodiesel), ethanol gave the highest conversion of 72%, t-butanol 62%, 1-butanol 42%, n-propanol 42% and iso-propanol 24%, while only 15% methyl ester was observed with methanol. With coconut oil, 1-butanol and iso-butanol achieved 40% conversion, 1-propanol 16% and ethanol 35%, while only traces of methyl esters were observed using methanol. Studies on some fuel properties of palm kernel oil and its biodiesel showed that palm kernel oil had a viscosity of 32.40 mm2/s, a cloud point of 28°C and a pour point of 22°C, while its biodiesel fuel had a viscosity of 9.33 mm2/s, a cloud point of 12°C and a pour point of 8°C. Coconut oil had a viscosity of 28.58 mm2/s, a cloud point of 27°C and a pour point of 20°C, while its biodiesel fuel had a viscosity of 7.34 mm2/s, a cloud point of 5°C and a pour point of - 8°C. Some of the fuel properties compared favourably with international biodiesel specifications.
Discovery of PDKI, One of the Missing Links in Insulin Signal Transduction
Authors: Alessi D. R.
Published: January 2005

Historically, two strategies have been used to dissect the insulin signal transduction pathway. One was to start at the insulin receptor and work down the signal transduction pathway from the plasma membrane. The other was to select a physiological action of insulin, namely the mechanism by which insulin stimulates glycogen synthesis, and then work backwards towards the receptor. The hope was that eventually the groups working down from the top of the insulin signalling pathway would meet up with those working upwards from the bottom of the pathway. This has now happened, and in this lecture I will describe the recent advances that have linked the research from both ends of the insulin signal transduction pathway. I will also discuss how these findings have enabled pharmaceutical companies to embark on novel programmes to develop improved therapies for the treatment of diabetes in the future.
Structure and Assembly of the Spliceosomal snRNPs
Authors: Nagai K. , Muto Y. , Krummel D. A. Pomeranz , Kambach C. , Ignjatovic T. , Walke S. , Kuglstatter A.
Published: January 2005

The spliceosome is a macromolecular machine that carries out the excision of introns from eukaryotic pre-mRNAs and splicing together of exons. Four large RNA-protein complexes, called the U1, U2, U4/U6 and U5 small nuclear ribo-nucleoprotein particles (snRNPs), and some non-snRNP proteins assemble around three short conserved sequences within the intron in an ordered manner to form the active spliceosome. We aim to provide insight into the molecular details of the mechanism of pre-mRNA splicing through crystallographic studies of the snRNPs. We have solved the X-ray crystal structure of some snRNP proteins as part of either protein-protein complexes or RNA-protein complexes. These structures have provided an important insight into the overall architecture of the U1 and U2 snRNPs and the mechanisms of RNA-protein and protein-protein recognition.
Leptin expression in placental and fetal tissues: does leptin have a functional role?
Authors: Hoggard N. , Haggarty P. , Thomas L. , Lea R. G.
Published: January 2005

Leptin is expressed in the placenta and in certain fetal tissues; however, little is known with regard to the function of this hormone in these tissues. To date, most evidence suggests that placental and/or fetal leptin acts as a fetal growth factor, but this is far from clear. Leptin may also have physiological effects on the placenta, including angiogenesis, growth and immunomodulation. The effects of placental leptin, if any, on the mother may contribute to endocrine-mediated alterations in energy balance, such as the mobilization of maternal fat, which occurs during the second half of pregnancy. In this review we will address these and other issues related to the expression of both placental and fetal leptin.
Gene expression of leptin and uncoupling proteins: molecular end-points of fetal development
Authors: Villarroya F. , Brun S. , Giralt M. , Cámara Y. , Solanes G. , Iglesias R.
Published: January 2005

Uncoupling proteins (UCPs) are considered to be major determinants of energy expenditure in mammals. During development in rodents, the expression of the UCP genes occurs sequentially. UCP2 mRNA is expressed long before birth. UCP1 mRNA expression in brown adipose tissue (BAT) starts in the late fetal period, and the expression of UCP3 mRNA begins immediately after birth in BAT and skeletal muscle. The postnatal induction of UCP1 gene expression is due mainly to cold stimuli, whereas the switch-on of UCP3 mRNA expression after birth requires the stimulus of food intake, specifically of lipids in the mother's milk. However, UCP3 mRNA expression after birth is also highly sensitive to leptin, and administration of a single injection of leptin to neonatal mice that were not allowed to suckle partly mimicked the natural induction of UCP3 gene expression in BAT and skeletal muscle. The speed of the effects of leptin on UCP3 mRNA expression suggests a direct action on skeletal muscle and BAT. The injection of leptin produced minor effects on UCP1 mRNA expression, and no effects were observed on UCP2 mRNA. In summary, leptin appears to contribute to the regulation of UCP3 gene expression in the perinatal period. Whatever the mechanism of action of leptin in BAT and skeletal muscle, it is already functional at birth.
Physiological and pathological regulation of feto/placento/maternal leptin expression
Authors: Linnemann K. , Malek A. , Schneider H. , Fusch C.
Published: January 2005

There is clear evidence of placental leptin production, as shown recently in trophoblast cultures and by dual in vitro placenta perfusion (median production of 225 pg/min per g of tissue; 98.4% released into the maternal and 1.6% into the fetal circulation). However, the physiological impact for the mother and the fetus is unclear. The classical role of leptin is to provide information about energy stores to the central nervous system, and to reduce appetite if the energy stores are full. In pregnancy, maternal plasma leptin concentrations are elevated, and lack the well established correlation with body fat energy stores that is observed in non-pregnant women, indicating an alternative function for leptin during pregnancy and fetal development. Maternal and fetal plasma leptin levels are dysregulated in pathological conditions such as gestational diabetes, pre-eclampsia and intra-uterine growth retardation, representing an effect or a cause of disturbances in the feto/placento/maternal unit.
The role of distal tryptophan in the bifunctional activity of catalase-peroxidases
Authors: Regelsberger G. , Jakopitsch C. , Furtmüller P. G. , Rueker F. , Switala J. , Loewen P. C. , Obinger C.
Published: January 2005

Catalase-peroxidases are bifunctional peroxidases exhibiting an overwhelming catalase activity and a substantial peroxidase activity. Here we present a kinetic study of the formation and reduction of the key intermediate compound I by probing the role of the conserved tryptophan at the distal haem cavity site. Two wild-type proteins and three mutants of Synechocystis catalase-peroxidase (W122A and W122F) and Escherichia coli catalase-peroxidase (W105F) have been investigated by steady-state and stopped-flow spectroscopy. W122F and W122A completely lost their catalase activity whereas in W105F the catalase activity was reduced by a factor of about 5000. However, the mutations did not influence both formation of compound I and its reduction by peroxidase substrates. It was demonstrated unequivocally that the rate of compound I reduction by pyrogallol or o-dianisidine sometimes even exceeded that of the wild-type enzyme. This study demonstrates that the indole ring of distal Trp in catalase-peroxidases is essential for the two-electron reduction of compound I by hydrogen peroxide but not for compound I formation or for peroxidase reactivity (i.e. the one-electron reduction of compound I).
Lignin peroxidase structure and function
Authors: Piontek K. , Smith A. T. , Blodig W.
Published: January 2005

Lignin peroxidase (LiP) plays a central role in the biodegradation of the plant cell wall constituent lignin. LiP is able to oxidize aromatic compounds with redox potentials higher than 1.4 V (NHE) by single electron abstraction, but the exact redox mechanism is still poorly understood. The finding in our laboratory that the Cβ-atom of Trp171 carries a unique modification led us to initiate experiments to investigate the role of this residue. These experiments, employing crystallography, site-directed mutagenesis, protein chemistry, spin-trapping and spectroscopy, yielded the following results: (i) Trp171 is stereospecifically hydroxylated at its Cβ-atom as the result of an auto-catalytic process, which occurs under turnover conditions in the presence of hydrogen peroxide, (ii) Evidence for the formation of a Trp171 radical intermediate has been obtained using spin-trapping, in combination with peptide mapping and protein crystallography. (iii) Trp171 is very likely to be involved in electron transfer from natural substrates to the haem cofactor via LRET. (iv) Mutagenetic substitution of Trp171 abolishes completely the oxidation activity for veratryl alcohol, but not for artificial substrates. (v) Structural changes in response to the mutation are marginal. Therefore the lack of activity is due to the absence of the redox active indole side chain.
A new versatile peroxidase from Pleurotus
Authors: Ruiz-Dueñas F. J. , Camarero S. , Pérez-Boada M. , Martínez M. J. , Martínez A. T.
Published: January 2005

Lignin peroxidase (LiP) and manganese peroxidase (MnP) have been investigated in Phanero-chaete chrysosporium. A third ligninolytic peroxidase has been described in Pleurotus and Bjerkandera. Two of these versatile peroxidases (VPs) have been cloned, sequenced and characterized. They have high affinity for Mn2+, hydro-quinones and dyes, and also oxidize veratryl alcohol, dimethoxybenzene and lignin dimers. The deduced sequences show higher identity with Ph. chrysosporium LiP than MnP, but the molecular models obtained include a Mn2+-binding site. Concerning aromatic substrate oxidation, Pl. eryngii VP shows a putative long-range electron transfer pathway from an exposed trytophan to haem. Mutagenesis and chemical modification of this tryptophan and the acidic residues forming the Mn2+-binding site confirmed their role in catalysis. The existence of several substrate oxidation sites is supported further by biochemical evidence. Residue conservation in other fungal peroxidases is discussed.
Evolution of bioinorganic motifs in P450-containing systems
Authors: Degtyarenko K. N. , Kulikova T. A.
Published: January 2005

The choice of bioinorganic motifs by Nature results in a spectacular variety of active-site structures even within the same protein family. Here, we use the concept of the bioinorganic motif to discuss the function and evolution of P450-containing and other related systems. Apart from P450, these systems include a FAD flavoprotein or domain, a FMN domain, ferredoxins and cytochrome b5. Analysis of available complete genomes can shed light on what an ancestral P450-containing system could be.
Control of electron transfer in neuronal NO synthase
Authors: Daff S. , Noble M. A. , Craig D. H. , Rivers S. L. , Chapman S. K. , Munro A. W. , Fujiwara S. , Rozhkova E. , Sagami I. , Shimizu T.
Published: January 2005

The nitric oxide synthases (NOSs) are dimeric flavocytochromes consisting of an oxygenase domain with cytochrome P450-like Cys-ligated haem, coupled to a diflavin reductase domain, which is related to cytochrome P450 reductase. The NOSs catalyse the sequential mono-oxygenation of arginine to N-hydroxyarginine and then to citrulline and NO. The constitutive NOS isoforms (cNOSs) are regulated by calmodulin (CaM), which binds at elevated concentrations of free Ca2+, whereas the inducible isoform binds CaM irreversibly. One of the main structural differences between the constitutive and inducible isoforms is an insert of 40–50 amino acids in the FMN-binding domain of the cNOSs. Deletion of the insert in rat neuronal NOS (nNOS) led to a mutant enzyme which binds CaM at lower Ca2+ concentrations and which retains activity in the absence of CaM. In order to resolve the mechanism of action of CaM activation we determined reduction potentials for the FMN and FAD cofactors of rat nNOS in the presence and absence of CaM using a recombinant form of the reductase domain. The results indicate that CaM binding does not modulate the reduction potentials of the flavins, but appears to control electron transfer primarily via a large structural rearrangement. We also report the creation of chimaeric enzymes in which the reductase domains of nNOS and flavo-cytochrome P450 BM3 (Bacillus megaterium III) have been exchanged. Despite its very different flavin redox potentials, the BM3 reductase domain was able to support low levels of CaM-dependent NO synthesis, whereas the NOS reductase domain did not effectively substitute for that of cytochrome P450 BM3.
Regulation of sialomucin complex/Muc4 in the female rat reproductive tract
Authors: Carraway K. L. , Idris N.
Published: January 2005

Sialomucin complex (SMC/rat Muc4) is a hetero-dimeric glycoprotein complex composed of an anti-adhesive mucin subunit ascites sialoglyco-protein (ASGP)-1 and a transmembrane subunit ASGP-2. SMC expression is tightly regulated in the uterus, and its expression appears to block blastocyst implantation. Expression is controlled by steroid hormone levels in the uterine luminal epithelium, but not the uterine glandular epithelium, oviduct, cervix or vagina. Increased progesterone levels lead to downregulation of SMC in the uterine luminal epithelium at the time of receptivity for implantation. Transforming growth factor β (TGF-β) has been implicated as a factor in uterine progesterone responses. Studies on primary rat uterine luminal epithelial cells showed that both SMC protein and transcript are downregulated by TGF-β1, although SMC expression is not altered by treatments with oestrogen or progesterone. SMC is also down-regulated when epithelial cells are co-cultured with isolated uterine stromal cells. Oestradiol and anti-TGF-β block the stromal cell effect. These data indicate that uterine epithelial cells respond to hormones to downregulate SMC via an indirect effect on stromal cells involving paracrine action of TGF-β.
UNC-52/perlecan isoform diversity and function in Caenorhabditis elegans
Authors: Rogalski T. M. , Mullen G. P. , Bush J. A. , Gilchrist E. J. , Moerman D. G.
Published: January 2005

The unc-52 gene encodes the nematode homologue of mammalian perlecan, the major heparan sulphate proteoglycan of the extracellular matrix. This is a large complex protein with regions similar to low-density lipoprotein receptors, laminin and neural cell-adhesion molecules. Three major classes of UNC-52/perlecan isoforms are produced through alternative splicing, and these distinct proteins exhibit complex spatial and temporal expression patterns throughout development. The unc-52 gene plays an essential role in myofilament assembly in body-wall muscle during embryonic development.
Biochemical characterization of human DNA polymerase i provides clues to its biological function
Authors: Tissier A. , Frank E. G. , McDonald J. P. , Vaisman A. , Henestrosa A. R. Fernàndez deHenestrosa , Boudsocq F. , McLenigan M. P. , Woodgate R.
Published: January 2005

The human RAD30B gene has recently been shown to encode a novel DNA polymerase, DNA polymerase i (poli). The role of poli within the cell is presently unknown, and the only clues to its cellular function come from its biochemical characterization in vitro. The aim of this short review is, therefore, to summarize the known enzymic activities of poli and to speculate as to how these biochemical properties might relate to its in vivo function.
Eukaryotic mutagenesis and translesion replication dependent on DNA polymerase ζ and Rev I protein
Authors: Lawrence C. W. , Maher V. M.
Published: January 2005

Translesion replication is a mechanism that employs specialized DNA polymerases for promoting continued nascent strand extension at forks blocked by the presence of unrepaired DNA damage. In Saccharomyces cerevisiae at least, this process contributes only modestly to the ability of cells to tolerate DNA damage, but is a major source of DNA-damage-induced substitutions and frameshifts, and of spontaneous mutations. Translesion replication past many types of DNA damage in yeast depends on the activities of DNA polymerase ζ (pol ζ) and Revlp. Pol ζ is found in most, but not all, eukaryotes investigated, whereas Revlp appears to be universal. Genes encoding these enzymes are found in humans, and appear to perform functions similar to those in yeast.
New advances in the understanding of the role of steroids and steroid receptors in disease
Authors: Wiseman H. , Duffy R.
Published: January 2005

Steroids and related compounds are important in disease development and prevention, via steroid receptor-mediated and receptor-independent mechanisms. Interaction of endogenous oestrogens with the oestrogen receptor has unfortunate mitogenic effects in breast cancer. However, dietary consumption of non-steroidal weak oestrogens, such as the soy isoflavone phytoestrogens genistein and diadzein, is associated with a decreased breast cancer risk. This may arise in part from the suboptimal configuration induced in the transactivation helix of oestrogen receptor-β.
Structural and functional alterations in the androgen receptor in spinal bulbar muscular atrophy
Authors: McEwan I. J.
Published: January 2005

The androgen receptor is a member of the nuclear receptor superfamily, and regulates gene expression in response to the steroid hormones testosterone and dihydrotestosterone. Mutations in the receptor have been correlated with a diverse range of clinical conditions, including androgen insensitivity, prostate cancer and spinal bulbar muscular atrophy, a neuromuscular degenerative condition. The latter is caused by expansion of a polyglutamine repeat within the N-terminal domain of the receptor. Thus the androgen receptor is one of a growing number of neurodegenerative disease-associated proteins, including huntingtin (Huntington's disease), ataxin-1 (spinocerebellar ataxia, type 1) and ataxin-3 (spinocerebellar ataxia, type 3), which show expansion of CAG triplet repeats. Although widely studied, the functions of huntingtin, ataxin-1 and ataxin-3 remain unknown. The androgen receptor, which has a well-recognized function in gene regulation, provides a unique opportunity to investigate the functional significance of poly(amino acid) repeats in normal and disease states.
Oestrogens and their promiscuous receptors: confronting reality
Authors: Barnes S.
Published: January 2005

The binding sites of the oestrogen receptors α and β have a structural requirement for ligands with two oxygen atoms (one of which is phenolic) spaced 11–12 Å apart. They are open to many non-steroidal compounds, such as those from plants and the chemical industry. The importance of this interaction is the subject of current food safety research. This article examines the methods of assessment of oestrogenicity and their relationship to physiological events.
Co-ordinate regulation of genes involved in storage lipid mobilization in Arabidopsis thaliana
Authors: Rylott E. L. , Hooks M. A. , Graham I. A.
Published: January 2005

Molecular genetic approaches in the model plant Arabidopsis thaliana (ColO) are shedding new light on the role and control of the pathways associated with the mobilization of lipid reserves during oilseed germination and post-germinative growth. Numerous independent studies have reported on the expression of individual genes encoding enzymes from the three major pathways: β-oxidation, the glyoxylate cycle and gluconeogenesis. However, a single comprehensive study of representative genes and enzymes from the different pathways in a single plant species has not been done. Here we present results from Arabidopsis that demonstrate the co-ordinate regulation of gene expression and enzyme activities for the acyl-CoA oxidase- and 3-ketoacyl-CoA thiolasemediated steps of β-oxidation, the isocitrate lyase and malate synthase steps of the glyoxylate cycle and the phosphoenolpyruvate carboxykinase step of gluconeogenesis. The mRNA abundance and enzyme activities increase to a peak at stage 2, 48 h after the onset of seed germination, and decline thereafter either to undetectable levels (for malate synthase and isocitrate lyase) or low basal levels (for the genes of β-oxidation and gluconeogenesis). The co-ordinate induction of all these genes at the onset of germination raises the possibility that a global regulatory mechanism operates to induce the expression of genes associated with the mobilization of storage reserves during the heterotrophic growth period.
Regulation of liver carnitine palmitoyltransferase I gene expression by hormones and fatty acids
Authors: Louet J.-F. , Le May C. , Pégorier J.-P. , Decaux J.-F. , Girard J.
Published: January 2005

This brief review focuses on the transcriptional regulation of liver carnitine palmitoyltransferase I (L-CPT I) by pancreatic and thyroid hormones and by long-chain fatty acids (LCFA). Both glucagon and 3,3′,5-tri-iodothyronine (T3) enhanced the transcription of the gene encoding L-CPT I, whereas insulin had the opposite effect. Interestingly, the transcriptional effect of T3 required, in addition to the thyroid-responsive element, the co-operation of a sequence located in the first intron of L-CPT I gene. Non-esterified fatty acids rather than acyl-CoA ester or intramitochondrial metabolite were responsible for the transcriptional effect on the gene encoding LCPT I. It was shown that LCFA and peroxisome proliferators stimulated L-CPT I gene transcription by distinct mechanisms. Peroxisome proliferator stimulated L-CPT I gene transcription through a peroxisome-proliferator-responsive element (PPRE) located at -2846 bp, whereas LCFA induced L-CPT I gene transcription through a peroxisome-proliferator-activated receptor α (PPARα)-independent mechanism owing to a sequence located in the first intron of the gene.
Mitochondrial respiration on rumenic and linoleic acids
Authors: Clouet P. , Demizieux L. , Gresti J. , Degrace P.
Published: January 2005

Rumenic acid (cis-9, trans-11-C18:2) represents approx. 80% of conjugated linoleic acid (CLA) in dairy products. CLA has been shown to exert beneficial effects on health, but little work has been devoted to the ability to oxidize CLA isomers and the role of these isomers in the modulation of β-oxidation flux. In the present study, respiration on rumenic acid was compared with that on linoleic acid (cis-9, cis-12-C18:2) with the use of rat liver mitochondria. In state-3, respiration was decreased by half with rumenic acid in comparison with linoleic acid. In the uncoupled state, respiration on CLA remained 30% lower. The lower ability to oxidize CLA was investigated through characterization of the enzymic steps. Rumenic acid was 33% less activated by acyl-CoA synthase than was linoleic acid. However, after such activation, the transfer of both acyl moieties to carnitine by carnitine acyltransferase I (CAT I) was of the same order. Moreover, CAT II activity was comparable with either isomer. After prior incubation with rumenic acid, oxidation of octanoic acid by re-isolated mitochondria was unimpaired, but that of palmitoleic acid was impaired unless linoleic acid was used in the prior incubation. The slower respiration on cis-9, trans-11-C18:2 is suggested to arise from lower carnitine-acylcarnitine translocase activity towards the acylcarnitine form, causing an upstream increase in the corresponding acyl-CoA.
Role of reactive oxygen species in cell signalling pathways
Authors: Hancock J. T. , Desikan R. , Neill S.J.
Published: January 2005

Reactive oxygen species (ROS) were originally thought to only be released by phagocytic cells during their role in host defence. It is now clear that ROS have a cell signalling role in many biological systems, both in animals and in plants. ROS induce programmed cell death or necrosis, induce or suppress the expression of many genes, and activate cell signalling cascades, such as those involving mitogen-activated protein kinases.
Regulation of clathrin-coated vesicle formation
Authors: Hill E. , Olusanya O. , van der Kaay J. , Downes C. P. , Andrews P. D. , Swedlow J. R. , Smythe E.
Published: January 2005

The formation of clathrin-coated pits at the plasma membrane requires the concerted action of many different molecules. The real challenge lies in determining the hierarchy of these interactions. We are using assays in both intact and permeabilized cells to dissect the temporal requirements for clathrin-coated vesicle formation, and also to examine the role of phosphorylation of the coat proteins.
Molecular determinants in pleckstrin homology domains that allow specific recognition of phosphoinositides
Authors: Lemmon M. A. , Ferguson K. M.
Published: January 2005

More than 250 pleckstrin homology (PH) domains have been identified in the human proteome. All PH domains studied to date appear to bind phosphoinositides, most binding only weakly and non-specifically. Members of a small subclass of PH domains show both high affinity and specificity for particular phosphoinositides, and recent structural studies have provided detailed views of these specific interactions. We discuss the architecture of the specific phosphoinositide-binding sites of PH domains, and how selectivity can be modulated by sequence changes.
HMG1 and 2: architectural DNA-binding proteins
Authors: Thomas J. O.
Published: January 2005

HMG1 and 2 (high mobility group proteins 1 and 2; renamed HMGB1 and 2) contain two DNA-binding HMG-box domains (A and B) and a long acidic C-terminal domain. They bind DNA without sequence specificity, but have a high affinity for bent or distorted DNA, and bend linear DNA. The individual A and B boxes (which, although broadly similar, show both structural and functional differences) exhibit many of the structure-specific properties of the whole protein. The acidic tail modulates the affinity of the tandem HMG boxes in HMG1 and 2 for a variety of DNA targets, including four-way junctions, but not distorted DNA minicircles, to which the proteins bind with very high affinity. HMG1 and 2 appear to play important architectural roles in the assembly of nucleoprotein complexes in a variety of biological processes, for example V(D)J recombination, the initiation of transcription, and DNA repair.
Redox signalling in chloroplasts and mitochondria: genomic and biochemical evidence for two-component regulatory systems in bioenergetic organelles
Authors: Forsberg J. , Rosenquist M. , Fraysse L. , Allen J. F.
Published: January 2005

Redox chemistry is central to the primary functions of chloroplasts and mitochondria, that is, to energy conversion in photosynthesis and respiration. However, these bioenergetic organelles always contain very small, specialized genetic systems, relics of their bacterial origin. At huge cost, organellar genomes contain, typically, a mere 0.1 % of the genetic information in a eukaryotic cell. There is evidence that chloroplast and mitochondrial genomes encode proteins whose function and biogenesis are particularly tightly governed by electron transfer. We have identified nuclear genes for ‘bacterial’ histidine sensor kinases and aspartate response regulators that seem to be targeted to chloroplast and mitochondrial membranes. Sequence similarities to cyano-bacterial redox signalling components indicate homology and suggest conserved sensory and signalling functions. Two-component redox signalling pathways might be ancient, conserved mechanisms that permit endogenous control over the biogenesis, in situ, of bioenergetic complexes of chloroplasts and mitochondria.
Can we identify the forces that drive the folding of integral membrane proteins?
Authors: Booth P. J. , Templer R. H. , Curran A. R. , Allen S. J.
Published: January 2005

Protein folding has been at the forefront of molecular cell biology research for several years. However, integral membrane proteins have eluded detailed molecular level study until recently. One reason is the often apparently insurmountable problem of mimicking the natural membrane bilayer with lipid or detergent mixtures. There is nevertheless a large body of information on lipid properties and in particular on phosphatidylcholine and phosphatidylethanolamine lipids, which are common to many biological membranes. We have exploited this knowledge to design efficient in vitro, lipid-bilayer folding systems for membrane proteins. Bacteriorhodopsin has been used as a model system for our initial studies: we have shown that a rate-limiting apoprotein folding step and the overall folding efficiency seem to be controlled by particular properties of the lipid bilayer. The properties of interest are the stored curvature elastic energy within the bilayer and the lateral pressure that the lipid chains exert on their neighbouring folding protein. These are generic properties of the bilayer that can be achieved with simple mixtures of many types of biological lipid and seem to be important in vivo.
Possible role for molecular chaperones in assembly and repair of photosystem II
Authors: Schroda M. , Kropat J. , Oster U. , Rüdiger W. , Vallon O. , Wollman F.-A. , Beck C. F.
Published: January 2005

Genes of the HSP70 chaperone family are induced by light. In Chlamydomonas reinhardtii, the induction of HSP70 (70 kDa heat shock protein) chaperones by light results in a partial protection of photosystem II against damage by photoinhibitory conditions. Underexpression of a chloroplast-localized HSP70 protein caused an increased sensitivity of photosystem II to light. Overexpression of this protein had a protective effect. Fluorescence measurements and studies of the turnover of photosystem II core components suggest that this HSP70 might function in both the protection and the regeneration of photosystem II. This concept is supported by fractionation studies in which the plastid HSP70 was found associated with chloroplast membranes. Because the light-induced elevation of HSP70 levels provides protection for photosystem II, we examined whether the chloroplast is involved in this regulation and found that mutants defective in plastid-localized chlorophyll synthesis, i.e. the insertion of Mg2+ into protoporphyrin IX are impaired in the induction of HSP70 by light. Exogenous addition of Mg-protoporphyrin in the dark induced the genes. The combined results support a model in which chlorophyll precursors are essential in the signalling from chloroplast to nucleus that regulates the chaperone genes.
AAA proteases of mitochondria: quality control of membrane proteins and regulatory functions during mitochondrial biogenesis
Authors: Langer T. , Käser M. , Klanner C. , Leonhard K.
Published: January 2005

An ubiquitous and conserved proteolytic system regulates the stability of mitochondrial inner membrane proteins. Two AAA proteases with catalytic sites at opposite membrane surfaces form a membrane-integrated quality control system and exert crucial functions during the biogenesis of mitochondria. Their activity is modulated by another membrane-protein complex that is composed of prohibitins. Peptides generated upon proteolysis in the matrix space are transported across the inner membrane by an ATP-binding cassette transporter. The function of these conserved components is discussed in the present review.
Mutations inactivating mitochondrial genes in Chlamydomonas reinhardtii
Authors: Remacle C. , Duby F. , Cardol P. , Matagne R. F.
Published: January 2005

Chlamydomonas reinhardtii is now becoming a useful model for the study of mitochondrial genetics in a photosynthetic organism. The small (15.8 kb) mitochondrial genome C. reinhardtii has been sequenced completely and all the genes have been identified. Several mutants inactivated in mitochondrial genes encoding components of the respiratory complexes I, III and IV have been characterized at the molecular level. Assembly of complex I in several mutant strains and mapping of mitochondrial mutations by recombinational analysis are also described.
Auxiliary functions in photosynthesis: the role of the FtsH protease
Authors: Bailey S. , Silva P. , Nixon P. , Mullineaux C. , Robinson C. , Mann N.
Published: January 2005

Oxygenic photosynthesis can be described effectively by using two long-standing models: the Z-scheme and the chemiosmotic hypothesis. However, these models do not reveal the dynamic nature of the thylakoid membrane and the four major complexes that it binds. The composition of the photosynthetic apparatus is continually changing in response to a range of environmental stimuli. In addition, many photosynthetic components have some of the highest turnover rates in Nature. Changes in composition and turnover of photosynthetic components require the degradation of existing and damaged polypeptides and the resynthesis and co-ordinated assembly of new polypeptides and their associated cofactors. This is achieved by several auxiliary functions, including proteolysis, protein targeting and the action of molecular chaperones. Some of the components involved in these functions, such as translocons, chaperones and proteases, have been identified but many of the auxiliary functions of photosynthesis remain uncharacterized. Among the proteases known to be associated with the thylakoids is the zinc metalloprotease FtsH, which might also act as a chaperone. Here we provide an overview of the thylakoid FtsH protease and discuss its role in the maintenance and assembly of the photosynthetic apparatus.