{Omega}-3 and {omega}-6 polyunsaturated fatty acids block HERG channels

Dietary polyunsaturated fatty acids (PUFAs) have been reported to exhibit antiarrhythmic properties, which have been attributed to their availability to modulate Na⁺, Ca²⁺, and several K⁺ channels. However, their effects on human ether-a-go-go-related gene (HERG) channels are unknown. In this study we have analyzed the effects of arachidonic acid (AA, -6) and docosahexaenoic acid (DHA, -3) on HERG channels stably expressed in Chinese hamster ovary cells by using the whole cell patch-clamp technique. At 10 µM, AA and DHA blocked HERG channels, at the end of 5-s pulses to –10 mV, to a similar extent (37.7 ± 2.4% vs. 50.2 ± 8.1%, n = 7–10, P > 0.05). 5,6,11,14-Eicosatetrayenoic acid, a nonmetabolizable AA analog, induced effects similar to those of AA on HERG current. Both PUFAs shifted the midpoint of activation curves of HERG channels by –5.1 ± 1.8 mV (n = 10, P < 0.05) and –11.2 ± 1.1 mV (n = 7, P < 0.01). Also, AA and DHA shifted the midpoint of inactivation curves by +12.0 ± 3.9 mV (n = 4; P < 0.05) and +15.8 ± 4.3 mV (n = 4; P < 0.05), respectively. DHA and AA accelerated the deactivation kinetics and slowed the inactivation kinetics at potentials positive to +40 mV. Block induced by DHA, but not that produced by AA, was higher when measured after applying a pulse to –120 mV (IO). Finally, both AA and DHA induced a use-dependent inhibition of HERG channels. In summary, block induced by AA and DHA was time, voltage, and use dependent. The results obtained suggest that both PUFAs bind preferentially to the open state of the channel, although an interaction with inactivated HERG channels cannot be ruled out for AA. K⁺ channel; membrane currents; ion channels; arrhythmia; antiarrhythmics     

Transcription of the {beta}-galactoside {alpha}2,6-sialyltransferase gene in B lymphocytes is directed by a separate and distinct promoter{dagger}

A single human gene, SIAT1, encodes the ß-galactoside     

A novel {beta}-galactosidase gene isolated from the bacterium Xanthomonas manihotis exhibits strong homology to several eukaryotic {beta}-galactosidases

The gene encoding a ß-galactosidase from Xanthomonasmanihotis was cloned into Escherichia coli. The gene resideson a 2.4 kb DNA fragment which was isolated from a partial Sau3Alibrary in the cloning vector pUC19 using 5-bromo-4-chloro-3-indolyl-ß-D-galactopyranoside(X-gal) as the selection. The enzyme produced by the clone hasa specificity for ß1-3->ß1-4-linked galactose.The nucleotide sequence of the gene was determined. The deducedprotein sequence contained 597 amino acids yielding a monomericmolecular mass of 66 kDa. The cloned ß-galactosidaseshowed no similarity to any known prokaryotic ß-galactosidase.However, extensive similarity was observed with eukaryotic ß-galactosidasesfrom animals, plants and fungi. The strongest similarity waswith the ß-galactosidases found hi the human and mouselysosomes (42 and 41% identity, respectively). Alignment ofthe X.manihotis and eukaryotic ß-galactosidase sequencesrevealed seven highly conserved domains common to each protein.Additionally, Domain 1 in X.manihotis showed similarity to regionswithin catalytic domains from seven xylanases and cellulasesbelonging to family 10 of glucosyl hydrolases. A region spanningDomain 2 showed similarity to the catalytic domain of endo ß1-3glucanases from tobacco and barley. cellulase ß-galactosidase G_M$$$gangliosidosis Morquio B syndrome Xanthomonas     

Characterization of serum {beta}-glucuronyltransferase involved in chondroitin sulfate biosynthesis

We studied a glucuronyltransferase involved in chondroitin sulfate(CS) biosynthesis in a preparation obtained from fetal bovineserum by heparin-Sepharose affinity chromatography. This enzymetransferred GlcA from UDP-GlcA to the nonreducing GalNAc residuesof polymeric chondroitin. It required Mn²⁺ for maximal activityand showed a sharp pH optimum between pH 5.5 and 6.0. The apparentKm value of the glucuronyltransferase for UDP-GlcA was 51 µM.The specificity was investigated using structurally definedacceptor substrates, which consisted of chemically synthesizedtri-, penta-, and heptasaccharide-serines and various odd-numberedoligosaccharides with a GalNAc residue at the nonreducing terminus,prepared from chondroitin and CS by chondroitinase ABC digestionfollowed by mercuric acetate treatment. The enzyme utilizeda heptasaccharide-serine GalNAcß1-4GlcAß1-3GalNAcß1-4GlcAß1-3Galß1-3Galß1-4Xylß1-O-Serand a pentasaccharide-serine GalNAcß 4GlcAß1-3Galß1-3Galß1-4Xylß1-O-Seras acceptors. In contrast, neither a trisaccharide-serine Galß1-3Galß1-4Xylß1-O-Sernor an     

Sequence Analysis of a 25-kb Segment in the 17{degrees}-19{degrees} Region of the Bacillus subtilis Chromosome Containing ada Locus

As a part of the Bacillus subtilis genome sequencing project,we have determined a 25-kb sequence covering the 17°–19°region. This region contains 26 complete open reading frames(ORFs) including the alkA and adaA/B operon, which encode genesfor adaptive response to DNA alkylation. A homology search forthe newly identified 21 ORFs revealed that 4 of them exhibita significant similarity to known proteins, e.g., methicillin-resistantStaphylococcus aureus (MRSA) protein homolog, proteins involvedin chloramphenicol resistance, glucosamine synthase and an ABCtransporter protein. The remaining 17 ORFs did not show anysignificant sequence similarities to known gene products inthe database.     

Sequence Analysis of the Bacillus subtilis 168 Chromosome Region between the sspC and odhA Loci (184{degrees}-180{degrees})

The nucleotide sequence of 45,389 bp in the 184°-;180°region of the Bacillus subtilis chromosome, containing the cgecluster, which is controlled by the sporulation regulatory proteinGerE, was determined. Fifty-four putative ORFs with putativeribosome-binding sites were recognized. Seven of them correspondto previously characterized genes: cgeB, cgeA, cgeC, cgeD, cgeE,ctpA, and odhA. The deduced products of 25 ORFs were found todisplay significant similarities to proteins in the data banks.We have identified genes involved in detoxification, cell walls,and in the metabolism of biotins, purines, fatty acids, carbohydratesand amino acids. The remaining 22 ORFs showed no similarityto known proteins. Both an attachment site of the SPßprophage and 2 new putative DNA replication terminators wereidentified in this region.     

Nature of light-induced absorbance changes at 682 m{micro} and 702 m{micro} in photosynthesis of Anacystis nidulans

Light-induced absorbance changes in the region around the redabsorption band of chlorophyll a were measured in cells andlamella fragments of Anacystis nidulans. In both materials,absorbance decreases were observed at 702 mµ and 682 mµ.(The pigments are designated as P₇₀₀ and P₆₈₀.) The nature ofP₆₈₀ was investigated with special reference to its relationshipto P₇₀₀. In the cells, light absorbed by chlorophyll a causedan absorbance decrease at 682 mµ; Simultaneous illuminationwith light absorbed by phycocyanin caused a partial recoveryof the absorbance decrease. Similar results were observed withthe light-induced absorbance change at 702 mµ. This indicatesthat P₆₈₀ is also an electron carrier in the electron transportchain and occupies a place between the two photoreactions. Inlamella fragments, both the light-induced reversible absorbancechanges of P₆₈₀ and P₇₀₀ appeared in the presence of an electrondonor system; i.e., ascorbate and 2,6-dichlorophenolindophenolor N,N,N',N'-tetramethyl-l,4-phenylenediamine. The experimentsin which the oxidation-reduction potential of the reaction mediumwas changed showed that both P₆₈₀ and P₇₀₀ are one-electroncarriers, having a normal oxidation-reduction potential of 0.44v (assuming that the normal oxidation-reduction potential ofthe ferricyanide-ferrocyanide system is 0.409 v). A possibilitywas suggested that the absorbance change observed at 682 mµis another expression of the oxidation-reduction reaction ofP₇₀₀). (Received October 30, 1968; )     

Production and secretion of {alpha}-galactosidase and endo-{beta}-mannanase by carob (Ceratonia siliqua L.) endosperm protoplasts

Viable protoplasts were isolated for the first time from maturecarob (Ceratonia siliqua L.) endosperm tissue. After 5 d ofincubation 75% of the protoplasts were viable. During incubationthey underwent vacuolation and produced the carob endospermhydrolases, agalactosidase and endo-ß-mannanase, whichwere secreted in the incubation medium. The secretion of bothenzymes were under Ca²⁺ control. Many characteristics of -galactosidaseand endo-ß-mannanase production by protoplasts werethe same as those of whole endosperms: their production didnot require any hormonal signal and was inhibited in the presenceof ABA or the leachate from the carob endosperm/seed coat. Moderatewater stress (—2.0 MPa) neither affected the activityof these hydrolases nor their secretion by endosperm protoplast.However, when the osmoticum of protoplast incubation mediumwas higher, the production and secretion of both hydrolaseswere reduced. Comparison of the hydrolases activities in theincubation media of leached carob endosperms, which were incubatedunder normal and water stress (—1.5 MPa) conditions, withthe activities of the protoplast-secreted hydrolases indicatedthat (i) carob endosperm cell wall acts as a barrier for thesecreted enzymes and (ii) that water stress reduces the cellwall porosity of the carob endosperm cells, and thus the releaseof the secreted -galactosidase and endo-ß-mannanaseis inhibited. The isolation of carob endosperm protoplasts offersa potent experimental system for the study of aspects of endospermcell physiology, such as enzyme secretion Key words: Abscisic acid, carob endosperm, Ceratonia siliqua L, endo-ß-mannanase, -galactosidase, leachate, protoplasts, water stress     

Human melanoma and Chinese hamster ovary cells galactosylate n-alkyl-{beta}-glucosides using UDP gal:GlcNAc {beta}1,4 galactosyltransferase

We previously showed that human melanoma, CHO and other cellscan convert ß-xylosides into structural analogs ofganglioside G_M3. We have investigated several potential acceptorsincluding a series of n-alkyl-ß-D-glucosides (n =6–9). All were labeled with ³H-galactose when incubatedwith human melanoma cells. Octyl-ß-D-glucoside (GlcßOctyl)was the best acceptor, whereas neither octyl--D-glucoside norN-octanoyl-methylglucamine (MEGA 8) were labeled. Analysis ofthe products by a combination of chromatographic methods andspecific enzyme digestions showed that the acceptors first receiveda single Galß1,4 residue followed by an 2,3 linkedsialic acid. Synthesis of these products did not affect cellviability, adherence, protein biosynthesis, or incorporationof radio-labeled precursors into glycoprotein, glycolipid orproteoglycans. To determine which ß1,4 galactosyltransferase synthesized Galß1,4GlcßOctyl,we analyzed similar incubations using CHO cells and a mutantCHO line (CHO 761) which lacks GAG-core specific ß1,4galactosyltransferase. The mutant cells showed the same levelof incorporation as the control, eliminating this enzyme asa candidate. Thermal inactivation kinetics using melanoma cellmicrosomes and rat liver Golgi to galactosylate GlcßOctylshowed the same half-life as UDP-Gal:GlcNAc ß1,4 galactosyltransferase,whereas LacCer synthase was inactivated at a much faster rate.We show that GlcßOctyl is a substrate for purifiedbovine milk UDP-Gal:GlcNAc ß1,4 galactosyltransferaseFurthermore, the galactosylation of GlcßOctyl by CHOcell microsomes can be competitively inhibited by GlcNAc orGlcNAcßMU . These results indicate that UDP-Gal:GlcNAcß1,4 galactosyltransferase is the enzyme used forthe synthesis of the alkyl lactosides when cells or rat liverGolgi are incubated with alkyl ß glucosides. alkylglucosides galactosyltransferase glycolipid artificial acceptors     

Developmental Variation of the Neurotoxin, {beta}-N-Oxalyl-L-{alpha},{beta}-diamino propionic acid (ODAP), in Lathyrus sativus

Several species of the tribe Viceae (Leguminosae) produce non-proteinamino acids that are toxic to man and animals. The neurotoxinß-N-oxalyl-L-,ß-diamino propionic acid (ODAP)in cultivated Lathyrus sativus causes human neurolathyrism,a neurological disease resulting in the paralysis of lower limbs.Surveys have shown that there are large scale variations betweenspecies of Lathyrus and varieties of L. sativus for the amountof cellular ODAP. In the present investigation, thin-layer chromatographyand chemical analysis were used to study developmental variationin the amount of ODAP in tissues and organs of L. sativus. Theresults confirmed that the rate of synthesis and accumulationof ODAP varied during plant development. Increased rates ofsynthesis were confirmed in young seedlings and in the developingfruits of L. sativus.Copyright 1994, 1999 Academic Press Lathyrus sativus, neurotoxin, ODAP, plant development     

Proton NMR study of triantennary complex type N-linked glycan chains: assignment of proton chemical shifts of the {beta}-Man residue in a basic unit of the triantennary glycan chain having a GlcNAc{beta}1->6Man{alpha}1->6Man{beta}->sequence

The chemical shifts of ring protons of the ß-Man residuein a triantennary complex type N-linked glycan chain havinga GlcNAcß1     

Molecular Cloning and Characterization of a cDNA for the r{beta} Subunit of a G Protein from Rice

We isolated a cDNA for the rß subunit of a heterotrimericG protein from rice (Oryza sativa L. cv. Nipponbare). The aminoacid sequence deduced from the cDNA was 76% and 94% homologusto the sequences of the rß subunits from Arabidopsisand maize (AGrß1 and ZGrß1), respectively. (Received July 28, 1995; Accepted December 25, 1995)     

Levels of {beta}-Glucan and Lignin in Elongating Internodes of Deepwater Rice

Partial submergence or treatment with either ethylene or gibberellicacid (GA₃ induces rapid growth in deepwater rice (Oryza sativaL.). We correlated the synthesis of two cell wall componentswith two phases of internodal elongation, namely (13,14)-ß-glucanformation with cell elongation and lignification with differentiationof the secondary cell wall and cessation of growth. The contentof ß-glucan was highest in the zone of cell elongationin internodes of air-grown plants and plants that were inducedto grow rapidly by submergence. In the intercalary meristemand in the differentiation zone of the internode, ß-glucanlevels were ca. 70% lower than in the zone of cell elongation.The outer cell layers, enriched in epidermis, contained moreß-glucan in submerged, rapidly growing internodesthan in air-grown, control internodes. The ß-glucancontent of the inner, parenchymal tissue was unaffected or slightlylowered by submergence. The epidermis appears to be the growth-limitingstructure of rapidly growing rice internodes. We hypothesizethat elevated levels of ß-glucan contribute to elongationgrowth by increasing the extensibility of the cell wall. Lignificationwas monitored by measuring the content of lignin and the activitiesof two enzymes of the lignin biosynthetic pathway, coniferylalcohol dehydrogenase (CAD) and phenylalanine ammonia-lyase(PAL), in growing and non-growing regions of the internode.Using submerged whole plants and GA₃-treated excised stem segments,we showed that lignin content and CAD activity were up to sixfoldlower in newly formed internodal tissue of rapidly growing ricethan in slowly growing tissue. No differences were observedin parts of the internode that had been formed prior to inductionof growth. PAL activity was reduced throughout the internodeof submerged plants. We conclude that lignification is one ofthe processes that is suppressed to permit rapid growth. ¹ This work was supported by the National Science Foundationthrough grants No. DCB-8718873 and DCB-9103747 and by the Departmentof Energy through grant No. DE-FGO2-90ER20021. M.S. was therecipient of a fellowship from the Max Kade Foundation.     

Development of {beta}-amylase activity and polymorphism in wheat seedling shoot tissues8

Increasing ß-amylase activity in wheat (Triticum aestlvum,var. Star) seedling shoot tissues was consistently accompaniedby the development of a characteristic polymorphism of the enzyme,as shown by electrophoresis employing amylopectin-containingpolyacrylamide gels. Very young shoot tissue contained one principalform of the enzyme (ß1), whereas two other major forms(ß2, ß3) appeared complementary to thisupon further growth. In vitro incubation experiments indicatedthat the polymorphism arose via a probably proteolytic conversionof ß1 into ß2 and ß3. The conversioninvolved neither an activation of ß-amylase nor asignificant modification of ß-amylase component plvalues. The electrophoretic ß-amylase patterns ofsubcellular leaf compartments suggested that ß1 issynthesized in the cytoplasm of leaf mesophyfi cells and thatthe other forms arise upon transfer of this ‘primary’form into the vacuole. The development of shoot ß-amylaseactivity did not require light, but appeared to be under thenegative control of the chloroplast and was stimulated by mineralnutrients. No clear relationship between ß-amylaseactivity and starch metabolism was evident, since the leaf activitywas largely absent from mesophyll protoplasts, could not beunequivocally demonstrated in the mesophyll chioroplasts, anddeveloped regardless of whether the tissues contained significantamounts of starch or not. Key words: Wheat, leaves, ß-amylase, polymorphism, compartmentation     

Effect of light treatment and endogenous growth hormones on {alpha}-and {beta}-amylase activities in cotyledons of Phaseolus vulgaris L.

The influence of light and endogenous plant-growth regulatorson the evolution of - and ß-amylases in cotyledonsof Phaseolus vulgaris L. was investigated. Both enzymes, whichare not present in ungerminated seeds, appear during germinationof intact seedlings or incubation of excised cotyledons. -Amylaseactivity decreases upon exposure to light. This inhibition iscorrelated with a drastic increase in chlorophyll content anda change in the endogenous gibberellin-inhibitor balance. ß-Amylaseactivity was not affected by light treatment but was by thepresence of endogenous cytokinins. (Received February 3, 1977; )     

Expression of {beta}-galactoside {alpha}2,6 sialyltransferase blocks synthesis of polysialic acid in Xenopus embryos

Polysialic acid is a developmentally regulated carbohydratestructure found on neural cell adhesion molecules (NCAM). Expressionof ß-galactoside 2,6-sialyltransferase in Xenopusembryos, by injection of mRNA, prevents the polysialylationof NCAM, presumably by introducing a different type of sugarlinkage that terminates chain elongation. Abnormalities in neuraldevelopment result from this treatment, but in general the bodyplan of the injected embryos is not severely affected. The resultsprovide evidence that the mis-expression of glycosyltransferasescan be used to interfere with the normal pattern of glycosylationin whole organisms. glycosylation NCAM polysialic acid Xenopus development     

Column Chromatographic Separation of Chlorophyllide {alpha} and Pheophorbide {alpha}

Chlorophyllide a, pheophorbide a, chlorophyll a and pheophytina were separated in a short time by anion-exchange chromatographywith a short column of DEAE-Sepharose CL-6B. (Received February 16, 1984; Accepted April 13, 1984)     

r{beta}Carotene Hydroxylase Gene from the Cyanobacterium Synechocystis sp. PCC6803

The ORF sll1468 of Synechocystis sp. PCC6803 was identifiedas a gene for rß-carotene hydroxylase by functionalcomplementation in a rß-carotene-producing Escherichiacoll. The gene product of ORF sll11468 added hydroxyl groupsto the rß-ionone rings of rß-carotene (rß,rß-carotene)to form zeaxanthin (rß,rß-carotene-3,3'-diol).This newly identified rß-carotene hydroxylase doesnot show overall amino acid sequence similarity to the knownrß-carotene hydroxylases. However, it showed significantsequence similarity to rß-carotene ketolases of marinebacteria and a green alga. (Received November 29, 1997; Accepted March 6, 1998)     

Studies on the {beta}-glucosidase System of Trifolium repens L.

Using DEAE-cellulose two distinct ß-glucosidase enzymeshave been identified in white clover; one form is primarilyassociated with the seed, the other with young leaves. Evidenceis presented for the separate nature of ß-glucosidaseand ß-galactosidase activity in dry seed flour andin young leaf tissue. These results are considered in relationto the function of the Li locus in white clover, which is shownto control both ß-glucosidase and ß-galactosidaseactivity in expanding leaves.