Carotenoids of Rowan Berries

The berries of Sorbus aucuparia have been investigated for theircarotenoid contents. The pigments identified were: phytofluene,-, ß-carotene, cryptoxanthin, monoepoxy--carotene,monoepoxy-ß-carotene, aurochrome, and mutatochrome.Usually when green fruits ripen the control of carotenoid synthesisis removed when the chlorophylls disappear, there is a rapidincrease of carotenoids in an over-all oxidative manner anddifferent carotenoids appear. However, the results obtainedsuggest that a different mechanism takes place in S. aucuparia.This may be the exception that proves the rule.     

Natural occurrence of phycoerythrocyanin-like pigment in cyanobacterial blooming samples dominated by Microcystis in Lake Kasumigaura

We describe the occurrence of phycocyanin and phycoerythrocyanin-likepigment in natural Microcystis colonies collected in Lake Kasumigaura.For differentiating pigments, the combination of simultaneousdetermination of molecular weights of and ß and subunitsby electrospray ionization mass spectrometry with HPLC separationand fluorescence measurements was used. It was suggested thatthe natural Microcystis colonies may contain the phycoerythrocyanin-likepigment, judged from the excitation and emission spectra. Measuredpigments consisted of different molecular weights of and ßsubunits, but the molecular weights of and ß subunitsin both phycocyanin and phycoerythrocyanin-like pigments werenot always identical.     

Release of Cell Body Agglutinins into the Medium from Gametes of Chlamydomonas reinhardtii upon Treatment with Proteases

Brief treatment of mt⁺ gametes of Chlamydomonas reinhardtiiwith trypsin or -chymotrypsin resulted in complete loss of flagellaragglutinability, without loss of cell motility, and concomitantrelease of cell body agglutinins (CBAs) into the culture medium.Release of CBAs also occurred when walled gametes without flagellawere treated with proteases. ¹Present address: Department of Biology, Washington UniversitySt. Louis, MO 63130, U.S.A.     

Chlorophyll-Carotenoid Protein Complexes from the Diatom, Phaeodactylum Tricornutum: Spectrophotometric, Pigment and Polypeptide Analyses

Chloroplast membranes of the diatom Phaeodactylum tricornutumwere dissociated by means of mild detergents, digitonin andlauryl-dimethylamide oxide. After electrophoresis on polyacrylamidegel, all the pigments were still attached to proteins, and sixpigment-protein complexes were obtained. Three Chl -ß-carotenecomplexes had the characteristics of Photosystem I and PhotosystemII antennae. The other three contained Chl , Chl c and fucoxanthinand were related to light-harvesting complexes. Chlorophyllide, a product of the hydrolysis of Chl by chlorophyllase, hasbeen found only in light-harvesting complexes. The spectralproperties, pigment and polypeptide compositions of the complexesare discussed in relation to those of other plants and to theparticular organization of the chloroplasts of diatoms. (Received December 20, 1986; Accepted April 14, 1987)     

Serum response factor mRNA induction in the hypertrophying chicken patagialis muscle

Gene expression inthe stretched chicken patagialis (Pat) muscle has not been extensivelyexamined. This study's purpose was to determine the Pat muscle'sexpression pattern of serum response factor (SRF), skeletal -actin,and MyoD mRNAs after 3 days (onset of stretch), 6 days (end of firstweek of rapid growth), and 14 days (slowed rate of stretch-inducedgrowth) of stretch. SRF mRNA demonstrated two species (B1 and B2), withB2 being more prevalent in the predominantly fast-twitch Pat muscle,compared with the slow-tonic muscle. Stretch overload increased B1 andB2 SRF mRNA concentrations, and the increase in B1 SRF mRNAconcentration was greater at day 6 compared with days 3 or14. MyoD mRNA concentration wasgreater in 3-day-stretched Pat muscles, compared withdays 6 or14 . Skeletal -actin mRNAconcentration was not changed during the study. Gel mobility shiftassays demonstrated that SRF binding with serum response element 1 ofthe skeletal -actin promoter had no altered binding patterns from6-day-stretched Pat nuclear extracts. It appears that SRF and MyoDmRNAs are induced in the stretch-overloaded Pat muscle but at differenttime points.

     

Molecular dynamics simulations of high-mannose oligosaccharides

Conformations of several high-mannose-type oligosaccharidesthat are generated during the biosynthetic degradation of Man₉GlcNAc₂to Man₅GlcNAc₂ have been studied by molecular dynamics (MD).Simulations were performed on NCI-FCRDC's Cray Y-MP 8D/8128supercomputer using Biosym's CVFF force field for 1000 Ps withdifferent initial conformations. The conformations of the two1,3- and the two 1,6-linkages in each oligomannose were different,suggesting that deriving oligosaccharide conformations basedon the conformational preferences of the constituent disaccharidefragments will not always yield correct results. Unlike otheroligomannoses, Man₉GlcNAc₂ appears to take more than one distinctconformation around the core 1,6-linkage. These various conformationsmay play an important role in determining the processing pathways.Using the data on the preferred conformations of these oligomannosesand the available experimental results, possible pathways forprocessing Man₉GlcNAc₂ to Man₅GlcNAc₂ by 1,2-linkage-specificmannosidases have been proposed. Conformational analysis ofMan₅GlcNAc₂ indicates that the addition of ß1,2-GlcNActo the 1,3-linked core mannose, besides serving as a prerequisitefor mannosidase II action as suggested earlier, may also preventthe removal of 1,3-mannose. The MD simulations also suggestthat the processing of the precursor oligosaccharide duringAsn-linked complex and hybrid glycan biosynthesis proceeds ina well-defined pathway involving more than one 1,2-linkage-specificmannosidase. Knowledge of the conformation of the processingintermediates obtained from the present study can be used todesign highly specific substrate analogues to inhibit a particularmannosidase, thereby blocking one processing pathway withoutinterfering with the others. carbohydrates conformation glycosidase inhibitors mannosidase oligosaccharide processing     

Xyloglucan and r{beta}-D-Glucan in Cell Walls of Rice Seedlings

Cell walls of 4-day old rice seedlings were extracted successivelywith ammonium oxalate-oxalic acid, 4% KOH and 24% KOH. A rß-D-glucanpreparation and a xyloglucan preparation were isolated fromthe 4% KOH extract and 24% KOH extract, respectively. Methylationanalysis and enzymic degradation studies of the polysaccharidesshowed that the former was built up predominantly of repeating-oligosaccharideunits of 3-O-rß-cellobiosyl-D-glucose and 3-O-rß-cellotriosyl-D-glucosein a molar ratio of 2.6 : 1.0, and the latter was of repeating-oligosaccharideunits of -D-xylosyl-(16)-rß-D-glucosyl-(14)-[-D-xylosyl-(16)]-rß-D-glucosyl-(14)-D-glucose,-D-xylosyl-(16)-rß-D-glucosyl-(14)-D-glucose and cellobiose. ¹ Present address: Department of Botany, Iowa State University,Ames, Iowa 50011, U.S.A. (Received August 29, 1981; Accepted January 12, 1982)     

Sialylation of intestinal microvillar membranes in newborn, sucking and weaned pigs

Affinity cytochemistry and biochemistry revealed distinctivetemporal changes in the expression of sialylated and compositionallyrelated membrane glycoconjugates in the pig small intestinebetween birth and weaning. The expression of membrane NeuAc2,6moieties, recognized by Sambucus nigra agglutinin-1, was highin newborn pigs, declined slightly during sucking and was verylow in weaned animals. Conversely, the expression of membraneNeuAc2r3 moieties, recognized by Maackia amurensis agglutinin-2,was low at birth but higher in sucking and weaned animals. Histobloodgroup O- and A-antigen expression was first detected in a minorityof sucking pigs, but was evident in all weaned pigs examined.Lactase glycoforms were isolated from solubilized microvillarmembranes of newborn and weaned pigs. The newborn (predominantly2,6-sialylated) and weaned (predominantly 1,2-fucosylated) glycoformsexhibited similar specific activity, indicating that postnatallactase decline in the pig intestine is unrelated to temporalchanges in membrane sialylation and fucosylation. fucosylation lactase lectins intestine sialylation     

An electrogenic Na(+)-HCO(-)(3) cotransporter (NBC) with a novel COOH-terminus, cloned from rat brain

We screened rat brain cDNA libraries and used 5'rapid amplification of cDNA ends to clone two electrogenicNa⁺-HCO₃ cotransporter(NBC) isoforms from rat brain (rb1NBC and rb2NBC). At the amino acidlevel, one clone (rb1NBC) is 96% identical to human pancreas NBC. Theother clone (rb2NBC) is identical to rb1NBC except for 61 uniqueCOOH-terminal amino acids, the result of a 97-bp deletion near the3' end of the open-reading frame. Using RT-PCR, we confirmed thatmRNA from rat brain contains this 97-bp deletion. Furthermore, wegenerated rabbit polyclonal antibodies that distinguish between theunique COOH-termini of rb1NBC (rb1NBC) and rb2NBC (rb2NBC).rb1NBC labels an ~130-kDa protein predominantly from kidney, andrb2NBC labels an ~130-kDa protein predominantly from brain.rb2NBC labels a protein that is more highly expressed in corticalneurons than astrocytes cultured from rat brain; rb1NBC exhibits theopposite pattern. In expression studies, applying 1.5%CO₂/10 mM HCO₃ toXenopus oocytes injected with rb2NBC cRNA causes 1)pH_i to recover from the initial CO₂-inducedacidification and 2) the cell to hyperpolarize. Subsequently,removing external Na⁺ reverses the pH_i increaseand elicits a rapid depolarization. In the presence of 450 µM DIDS,removing external Na⁺ has no effect on pH_i andelicits a small hyperpolarization. The rate of the pH_idecrease elicited by removing Na⁺ is insensitive toremoving external Cl. Thus rb2NBC is aDIDS-sensitive, electrogenic NBC that is predominantly expressed inbrain of at least rat.

     

A novel alpha1,2-fucosyltransferase (CE2FT-2) in Caenorhabditis elegans generates H-type 3 glycan structures

The 1,2-fucosyltransferase family (1,2FT) is the largest familyof glycosyltransferases in the genome of the free-living nematodeCaenorhabditis elegans, and early evidence suggests that eachmember may have a unique activity. Here we describe a C. elegansgene (designated CE2FT-2) encoding an 1,2FT that has the potentialto generate the sequence Fuc1-2Galβ1-3GalNAc-R, which isthe H-type 3 blood group structure. The CE2FT-2 cDNA encodesa putative transmembrane protein that shows 42% amino acid identityto a previously cloned C. elegans 1,2FT (termed CE2FT-1), buthas a very low identity (16–20%) to 1,2FT sequences inhumans, rabbits, and mice. A recombinant form of CE2FT-2 expressedin human 293T cells has a high 1,2FT activity toward Galβ1-3GalNAc-O-pNP,but unexpectedly, the enzyme is inactive toward the acceptorGalβ-O-phenyl. Thus, CE2FT-2 differs from all other 1,2FTspreviously described from animals that all utilize Galβ-O-phenyl.CE2FT-2 is expressed at all stages of worm development, butremarkably, promoter analysis of the CE2FT-2 gene using greenfluorescent protein reporter constructs indicates that the CE2FT-2is expressed exclusively in pharyngeal cells of the worm fromembryo to an adult stage. Because pharyngeal cells are knownto secrete their glycoconjugates to the nematode surface, theseresults may indicate that products of CE2FT-2 contribute tointeractions of the nematode with its environment or are usedas ligands for bacterial attachment. These findings, along withthose on other 1,2FTs in C. elegans, suggest that each 1,2FTin this organism may have a unique acceptor specificity, expressionpattern, and biological function.     

Pigment synthesis in Cucurbita moschata cotyledons as influenced by CPTA and several inhibitors

2-(4-Chlorophenylthio) triethylamine hydrochloride (CPTA) inducedthe accumulation of a number of carotenes in pumpkin (Cucurbitamoschata) cotyledons, a tissue which does not normally accumulatethese pigments. Lycopene accumulated concomitantly with a decreasein -carotene and ß-carotene. CPTA appeared to inhibitcyclases involved in the synthesis of -carotene and ß-caroteneand to stimulate enzymes involved in lycopene synthesis. Cycloheximidereduced this CPTA induced enzyme synthesis while diphenylaminereduced CPTA induced carotene accumulation. Actinomycin D alonereduced accumulation of carotenes, but it did not affect CPTAinduced carotene accumulation. Rather lutein, violoxanthin andneoxanthin decreased and -carotene and ß-caroteneaccumulated. ¹Present address: Morioka Branch, Vegetable and Ornamental CropsResearch Station, Ministry of Agriculture and Forestry, Shimokuriyagawa,Morioka, Japan. (Received August 12, 1974; )     

Colonic H-K-ATPase alpha- and beta-subunits express ouabain-insensitive H-K-ATPase

Active K absorption in the rat distal colon is energizedby an apical H-K-ATPase, a member of the gene family of P-type ATPases. The H-K-ATPase -subunit (HKc) has been cloned and characterized (together with the -subunit of either Na-K-ATPase or gastric H-K-ATPase) in Xenopus oocytes as ouabain-sensitive⁸⁶Rb uptake. In contrast, HKc, when expressed in Sf9cells without a -subunit, yielded evidence of ouabain-insensitiveH-K-ATPase. Because a -subunit (HKc) has recently been clonedfrom rat colon, this present study was initiated to determine whetherH-K-ATPase and its sensitivity to ouabain are expressed when these twosubunits (HKc and HKc) are transfected into a mammalian cellexpression system. Transfection of HEK-293 cells with HKc and HKccDNAs resulted in the expression of HKc and HKc proteins andtheir delivery to plasma membranes. H-K-ATPase activity was identified in crude plasma membranes prepared from transfected cells and was1) saturable as a function of increasing K concentration with aK_m for K of 0.63 mM; 2) inhibited byorthovanadate; and 3) insensitive to both ouabain andSch-28080. In parallel transfection studies with HKc and Na-K-ATPase1 cDNAs and with HKc cDNA alone, there was expression ofouabain-insensitive H-K-ATPase activity that was 60% and 21% of thatin HKc/HKc cDNA transfected cells, respectively. Ouabain-insensitive ⁸⁶Rb uptake was also identified incells transfected with HKc and HKc cDNAs. These studies establishthat HKc cDNA with HKc cDNA express ouabain-insensitiveH-K-ATPase similar to that identified in rat distal colon.

     

STEROLS OF CHLORELLA. I. THE NATURALLY OCCURRING STEROLS OF CHLORELLA VULGARIS, C. ELLIPSOIDEA, AND C. SACCHAROPHILA

The characteristics of the sterols naturally occurring in threespecies of Chlorella were examined. The algae were grown heterotrophicallyon glucose. Sterols were extracted and isolated from the lipidfraction and were characterized by means of chemical and physicaltests. Chlorella vulgaris contained three sterols. Only the principalone, chondrillasterol, was identified. Chondrillasterol hasbeen isolated previously from the genus Scenedesmus. Chlorella ellipsoidea and Chlorella saccharophila were foundto contain sterols with ß-oriented alkyl groups atC-24 in contrast to the -oriented groups commonly found in higherplants. Poriferasterol was identified as the principal sterolof both algae. Clionasterol and 22-dihydrobrassicasterol wereidentified as the two secondary sterols present. None of thesesterols have previously been reported to occur in plants. Theisolation of 22-dihydrobrassicasterol has not been previouslyreported from any natural source. ¹Scientific Article A1153, Contribution No. 3623 of the Universityof Maryland Agricultural Experiment Station. ²This work has been supported in part by a grant from the NationalAeronautics and Space Administration.     

A Transient Stimulation of Net Photosynthesis of Rye Leaves by {alpha}-Hydroxy-2-pyridinemethanesulphonic Acid ({alpha}-HPMS) due to Inhibition of Photorespiratory CO2 Release

The effects of -hydroxy-2-pyridinemethanesulphonic acid (-HPMS)upon net photosynthesis (P_n, the CO₂ compensation point (),post-lower illumination burst of CO₂ (PLIB) and post-lower temperatureburst of CO₂ (PLTB) in detached rye (Secale cereale L.) leaveswere investigated. At low concentrations ( 0.5 mol m^–3),-HPMS initially stimulated P_n and decreased the magnitude ofboth PLIB and PLTB. The decreased at all concentrations of-HPMS (0.05–5.0 mol m^–3. The effects of -HPMS onP_n and were time-dependent and, after a few minutes, the P_nwas inhibited while values increased considerably. At a higherconcentration (5.0 mol m ^–3), the transient effects of-HPMS were shorter () or not observed at all (P_n. Both PLIBand PLTB, when expressed in relation to P_n, increased at higherlevels of this compound. Similar data with respect to the effectsof -HPMS on PLIB and PLTB were found for leaves of dandelion(Taraxacum officinale L.). The results suggest that -HPMS may stimulate P_n by inhibitingphotorespiration, as originally suggested by Zelitch (1966),but only at low concentrations and over a short time span. Thedecrease of PLIB and PLTB values at low -HPMS levels is consistentwith these processes being a residual activity of the glycolatepathway. Key words: CO₂ compensation point, -hydroxy-2-pyridinemethanesulphonic acid, photorespiration, photosynthesis     

An NTP-Binding Protein That Cross with a Ras-Specific Antibody in the Myceia of Neurospora crassa

A Ras-related NTP-binding protein was partially purified froma membrane fraction derived from the mycelia of Neurospora crassa.[-³²P]ATP and [-³²P]GTP were incubated with mem brane and solublefractions which were then irradiated with UV light to inducecrosslinking of tightly bound nucleotides. After SDS-polyacrylamidegel electrophoresis, blotting onto a nitrocellulose filter andautoradiography it was apparent that most of the proteins thatbound [-³²P]-GTP also bound [-³²P]ATP. Pretreatment of the membranefraction with Ras-specific antibody effectively blocked thebinding of [-³²P]ATP and [-³²P]GTP to several ATP-GTP-bindingproteins. The band of a protein with a molecular weight of 26kDa on the SDS-polyacrylamide gel cross-reacted strongly withthe Ras-specific antibody. The protein was extracted from thegel and further purified by repeated gel electrophoresis. Thepurified protein bound [-³²P]ATP, [-³²P]-GTP, [-³²P]CTP and[-³²P]UTP at 1.6x10^– M and was autophosphorylated in thepresence of [-³²P]ATP and [-³²P]GTP at 1.7x10 M. Pretreatmentof the protein with Ras-specific antibody partially blockedthe autophosphorylation in the presence of these nucleotides.The binding of [-³²P]ATP to the NTP-binding protein was blockedby addition of ATP at 10^–4–10^–3 M. ATP ata concentration of 10^–4 M prevented the binding of [-³²P]to a greater extent than did GTP at the same concentration.Binding of [-³²P]CTP and [-³²P]UTP to the protein was also observed. (Received October 7, 1991; Accepted July 14, 1992)     

Inhibition of Gibberellic Acid-induced Starch Mobilization by Salicylhydroxamic acid in Avena fatua L. Seed

Inhibition of GA₃-induced endosperm mobilization in Avena fatuaL. by salicylhydroxamic acid (SHAM), a widely used alternativerespiration inhibitor, was studied. SHAM strongly inhibitedthe GA₃-induced release of reducing sugars in the incubationmedium by 3 mm de-embryonated endosperm segments; at 4 mM SHAM,GA₃-induced sugar release was inhibited by 66–79 per cent.Extracts prepared from segments incubated in 0.05 mM GA₃ with2, 5 and 10 mM SHAM showed 30, 53 and 71 per cent lower -amylaseactivity, respectively, compared to the GA₃-alone treatment.Addition of SHAM (0.5–5 mM) during the enzyme assay hadno effect on the activity of -amylase. Thus, the inhibitionof starch mobilization in endosperm by SHAM is due to inhibitionof the production and not the activity of -amylase. The inhibitionof Avena fatua seedling growth by SHAM reported earlier may,in part, be due to its effect on endosperm mobilization. Since (1) Avena fatua seeds have been shown to have little orno SHAM-sensitive respiration, and (2) concentrations of SHAMnecessary for inhibiting endosperm mobilization were significantlyhigher than those generally necessary for inhibiting alternativerespiration, the inhibition of endosperm mobilization by thiscompound does not appear to involve its effect on alternativerespiration. Avena fatua L., wild oat, -amylase, endosperm, gibberellic acid, salicylhydroxamic acid, seed     

Differential distribution of ERalpha and ERbeta mRNA in intrauterine tissues of the pregnant rhesus monkey

Twoestrogen receptor (ER) isoforms, ER and ER, have been described.However, no information is available in any species regarding thecomparison of ER and ER levels in pregnant intrauterine tissues.We investigated 1) distribution of ER and ER mRNA in myometrium, amnion, choriodecidua, and placenta; 2) theirabundance in intrauterine tissues at term not in labor (NIL) and inspontaneous term labor (STL); and 3) immunolocalization ofER and ER in pregnant rhesus monkey myometrium. Myometrium,amnion, choriodecidua, and placenta were obtained at cesarean sectionfrom monkeys in STL at 156-166 days gestational age(GA) (n = 4) and from control monkeys NIL at140-152 days GA (n = 4). RT-PCR was conducted to determineER and ER and glyceraldehyde-3-phosphate dehydrogenase mRNAabundance in four intrauterine tissues of the pregnant rhesus monkey.The cloned ER PCR fragment was subjected to sequence analysis. ERand ER were localized in the myometrium by immunohistochemistry. Wedemonstrated that 1) rhesus monkey ER shares >97%identity with human ER in the region sequenced; 2) both ERswere expressed in myometrium, amnion, and choriodecidua but not inplacenta in the current study; 3) ER and ER weredifferentially distributed in myometrium and amnion; 4) ERand ER were immunolocalized in myometrial smooth cells and smoothmuscle and endothelial cells of the myometrial blood vessels. Thebiological significance of these quantitative differences in ERsubtypes merits further study.

     

Inner core assembly and structure of the lipooligosaccharide of Neisseria meningitidis: capacity of strain NMB to express all known immunotype epitopes

Neisseria meningitidis expresses a heterogeneous populationof lipooligosaccharide (LOS) inner cores variously substitutedwith 1-3-linked glucose and O-3, O-6, and O-7 linked phosphoethanolamine(PEA), as well as glycine, attached to HepII. Combinations ofthese attachments to the LOS inner core represent immunodominantepitopes that are being exploited as future vaccine candidates.Historically, each LOS immunotype was structurally assessedand prescribed a certain unique inner core epitope. We reportthat a single isolate, strain NMB, possesses the capacity toproduce all of the known neisserial LOS inner core immunotypestructures. Analysis of the inner cores from parental LOS revealedthe presence or absence of 1,3-linked glucose, O-6 and/or O-7linked PEA, in addition to glycine attached at the 7 positionof the HepII inner core. Identification and inactivation oflpt-6 in strain NMB resulted in the loss of both O-6 and O-7linked PEA groups from the LOS inner core, suggesting that Lpt-6of strain NMB may have bifunctional transferase activities orthat the O-6 linked PEA groups once attached to the inner coreundergo nonenzymatic transfer to the O-7 position of HepII.Although O-3 linked PEA was not detected in parental LOS innercores devoid of 1-3-linked glucose residues, LOS glycoformsbearing O-3 PEA groups accumulated in a truncated mutant, NMBlgtK(Hep₂Kdo₂-lipid A). Because these structures disappeared uponinactivation of the lpt-3 locus, strain NMB expresses a functionalO-3 PEA transferase. The LOS glycoforms expressed by NMBlgtKwere also devoid of glycine attachments, indicating that glycinewas added to the inner core after the completion of the -chainby LgtK. In conclusion, strain NMB has the capability to expressall known inner core structures, but in in vitro culture L2and L4 immunotype structures are predominantly expressed.     

Mycobacterial arabinan biosynthesis: the use of synthetic arabinoside acceptors in the development of an arabinosyl transfer assay

Information on the biosynthesis of the D-arabinans of the cellwall of Mycobacterium tuberculosis is rapidly emerging, withthe promise of new targets for drug development against tuberculosis.Accordingly, arabinosyl transferase assays were developed utilizingsynthesized [1–¹⁴C]-β-D-arabinofuranosyl-1-monophosphoryldecaprenolas donor and a variety of O- and S-alkyl arabinosides as acceptors.These were: -D-Araf-(15)--D-Araf-O- and -S-alkyl di-arabinosidesand -D-Araf-(15)--D-Araf-(15)--D-Araf-O- and -S-alkyl triarabinosides.Whereas the O- and S-alkyl monosaccharide acceptors were inactive,the O- and S-alkyl disaccharide and the O- and S-alkyl trisaccharideacceptors (<C12) possessed considerable acceptor activity,and the trisaccharide acceptors were more potent than the correspondingdisaccharides. The O-alkyl disaccharide acceptors with a C8alkyl chain were more active than those containing the C6 orC10 analogs. Chemical analysis of the enzymatically synthesizedproducts of the reactions demonstrated that β-D-arabinofuranosyl-1-monophosphoryldecaprenolwas an effective donor for two of the three potential arabinosyltransferases: β-D-arabinofuranosyl-1-monophosphoryldecaprenol:arabinan (15) arabinosyl transferase and β-D-arabinofuranosyl-1-monophosphoryl-decaprenol:arabinan β(12) arabinosyl transferase. The β(12) arabinosyltransferase activity was more in evidence in the presence ofthe O-alkyl disaccharide acceptor, whereas both transferaseswere about equivalent in the presence of the S-alkyl trisaccharideacceptor. The tuberculosis drug, ethambutol, a known mycobacterialarabinosyl transferase inhibitor, was inactive within thesearabinosyl transferase/acceptor based assay systems, supportingother evidence that a third activity, responsible for the formationof 13 linkage, is the drug target. acceptor arabinan biosynthesis glycosyltrans-ferase assay mycobacteria