A Comparative View of Alpha Crystallins: The contribution of comparative studies to understanding function

Integration between comparative biology and cellular/molecularbiology has helped advance understanding of the structure, functionand physiology of the vertebrate small heat shock proteins A-and B-crystallin. These proteins are expressed at high concentrationin the eye lens where they contribute to transparency and refractivepower. But they also function similarly to molecular chaperonesby preventing the aggregation of denatured proteins that cancause opacities, or cataracts. -crystallins also serve a numberof other roles in and out of the lens that are still not completelyunderstood. Comparative examination of -crystallins and closelyrelated small heat shock proteins from diverse taxa has helpedprovide insights into the proteins' three-dimensional shapeand structure/function relationships. Until recently, no studieshad examined the tissue specific expression or chaperone-likeactivity of -crystallins from a non-mammalian vertebrate. Ihave been investigating the -crystallins of the zebrafish, Daniorerio, as a first step towards utilizing the bony fishes asa model group for understanding the evolution of -crystallinfunction. Zebrafish A-crystallin displays similar structureand expression and increased chaperone-like activity comparedto its human orthologue. Zebrafish B-crystallin, however, hasa truncated C-terminal extension, more limited expression andlower chaperone-like activity than its human orthologue. Thesedata suggest that A-crystallin physiological function may beconserved between zebrafish and mammals, while B-crystallinphysiological function has diverged. Understanding zebrafish-crystallin physiology is necessary before this species canbe used for developmental and genetic studies, and providesa foundation for further comparative studies.     

{alpha}Melanocyte Stimulating Hormone: Chemical Nature and Mechanism of Action

Melanotropin (-MSH) is a tridecapeptide, Ac-Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH₂,synthesized and secreted by the pars intermedia of the vertebratepituitary. This peptide hormone is derived from pro-opiomelanocortin,a precursor protein which contains within its structure thesequences of other melanotropic peptides (- and rß-MSH,corticotropin), and possibly other hormones. -MSH is the physiologicallyrelevant melanotropin secreted by the pituitary and in mostvertebrates plays the essential role in adaptive color changesthrough its action on integumental chromatophores. The initial actions of -MSH are mediated at the level of themelanocyte membrane and involve signal transduction from receptorto adenylate cyclase on the intracellular surface of the membrane.This results in elevated cytosolic cyclic AMP levels followedby melanosome dispersion within dermal melanocytes and melanogenesiswithin epidermal melanocytes. The action of -MSH on dermal melanocytesrequires calcium for transduction of signal and cyclic AMP production.Melanosome dispersion per se does not, however, require extracellularcalcium. Structure-function studies of -MSH analogues and fragmentshave provided important insights relative to the structuralrequirements of the hormone for receptor binding and transduction.Substitution of certain residues within -MSH has led to thedevelopment of melanotropins that exhibit extraordinary potencyand prolonged biological activity     

The Ontogeny of Osmoregulation and Its Neurosecretory Control In the Decapod Crustacean, Rhithropanopeus harrisii (Gould)

Laboratory-hatched larvae of this estuarine crab were rearedat 25°C in seawater of 25 salinity for 18 days coveringzoeal Stages I to IV and a megalops. Three-day periods betweenzoeal stages represent intermolt stages of circadean metecdysis,diecdysis, and proecdysis.Larvae were exposed to either a seriesof seawater salinities from 5-40 in 5 increments or of 10-40in 10 increments for one hour during each day of their development.The osmoconcentrations of 20-80 nanoliter hemolymph samplesfrom each of four larvae were measured separately by determinationsof freezing point depression. Eyestalkless larvae in metecdysis of zoeal Stage II were exposedto the same osmoconcentrations as unoperated controls to testfor osmoregulation by eyestalk nerve tissue. Larvae tend to be isosmotic with seawater of 30-40 salinity(S) and to hyperregulate in more dilute media except for larvaein their first diecdysis which remain isosmotic. Larvae in thelast few hours of proecdysis hyperregulate against 40 S as well,presumably to insure inflow of water to establish a greaterbody volume during hardening of the exoskeleton. They are consequentlyisosmotic in the very early metecdysis. The presence of eyestalks at the first metecdysis (Stage II)keeps zoeas hyperosmotic to 5-30 S, but prevents them from hyperregulationagainst 40 S. Eyestalkless zoeas become isosmotic with 5-30S and hyperregulate against 40 S like late proecdysal larvae.Lack of eyestalks makes diecdysal animals hyperregulate againsta medium with which normal animals are isosmotic. The eyestalkinfluence affects second metecdysal (Stage III) larvae in away similar to those in first metecdysis except that it apparentlyalso prevents a curious tendency to hyporegulate in 5-30 S.Similarly, in this stage, the eyestalks prevent hyperosmosityin 40 S seawater as they do during the first day of zoeal StageII. Eyestalk nerve tissue reduces the degree to which diecdysallarvae of this stage remain hyperosmotic to media of 10 S and20 S and apparently causes larvae to be hypoosmotic at 40 S. Preliminary data indicate that removal of eyestalks has littleeffect on proecdysal larval osmoregulation or on regulationof Stage IV zoeas. In other experiments ablation of eyestalks caused Stage II larvaeto lose the ability to osmoregulate against 10-30 S seawaterwithin two hours after the operation. The same zoeas did nothyperregulate against 40 seawater until four hours after removalof eyestalks.     

Ecdysone Metabolism in Insects

The current status of the pathway of ecdysone biosynthesis andinactivation in insects is discussed. Evidence is presenteddemonstrating that rß-ecdysone is generated from -ecdysoneby fat body, Malpighian tubules, gut, and body wall, but notby blood, oenocytes, muscle, salivary gland, or the prothoracicgland itself (in vitro experiments with prepupal Manduca sextatissues). Since -ecdysone does not appear to have demonstrablehormonal activity at physiological concentrations in in vitrotissue systems which cannot metabolize it to rß-ecdysone,it is suggested that -ecdysone serves as a prohormone ratherthan as a hormone. The role of the prothoracic gland in theproduction of -ecdysone remains to be defined.     

{delta}15N and {delta}13C Measurements of Antarctic Peninsula Fauna: Trophic Relationships and Assimilation of Benthic Seaweeds

Measurements of ¹³C, ¹⁵N, and C/N for a variety of Antarcticpeninsula fauna and flora were used to quantify the importanceof benthic brown algae to resident organisms and determine foodweb relationships among this diverse littoral fauna. ¹³C valuesranged from–16.8 for benthic algal herbivores (limpets)to –29.8 for the krill, Euphausia superba; the averagepooled value for brown macroalgae, including their attachedfilamentous diatoms, was–20.6. There was no correlationbetween biomass ¹³C or ¹⁵N with C/N content, and consequentlyboth ¹³C and ¹⁵N values were useful in evaluating trophic relationships.¹⁵N values of the fauna ranged from 3.1 to 12.5, with lowestvalues recorded in suspension feeders (e.g., bryozoans) andhighest values in Adelie penguins (12.5) collected in 1989.The comparatively lower ¹⁵N value for a Chinstrap penguin (6.9)collected in 1997 is attributed to the different dietary foodsources consumed by these species as reflected in their respective¹³C values. Significant amounts of benthic macroalgal carbonis incorporated into the tissues of invertebrates and fishesthat occupy up to four trophic levels. For many benthic andepibenthic species, including various crustaceans and molluscs,assimilation of benthic algal carbon through detrital pathwaysranges from 30 to 100%. Consequently, the trophic importanceof benthic brown algae may well extend to many pelagic organismsthat are key prey species for birds, fishes, and marine mammals.These data support the hypothesis that benthic seaweeeds, togetherwith their associated epiphytic diatoms, provide an importantcarbon source that is readily incorporated into Antarctic peninsulafood webs.     

Contractile Proteins of a Benthic Fish.I. Effects of Temperature and Pressure on Myosin ATPase.

SYNOPSIS. Studies are described on the adenosine triphosphatase(ATPase) properties of myosin isolated from skeletal muscleof Coryphaenoides, a benthic fish captured at 2,200 meters depth.Ca²⁺-ATPase and EDTA-ATPase of Coryphaenoides myosin show thesame pH dependence as ATPase of mammalian myosin; however, ratesof ATP hydrolysis by Coryphaenoides myosin are only 5–10%of rates of ATP hydrolysis by rabbit skeletal myosin. Coryphaenoidesmyosin ATPase shows a decrease from Q₁₀ of 2.0 at 25°C toQ₁₀ of 1.4 a t 2°C, and undergoes irreversible denaturationat temperatures above 25°C. At pH 6.8 to pH 8.5, Coryphaenoidesmyosin ATPase undergoes activation by pressure at 25°C,but at 2°C shows negligible effect of pressure at valuesbelow 3,000 psi. The kinetic data on Ca²⁺-ATPase indicate valuesof 11 kcal/mole for H, –7.5 kcal/mole for TS, and –5.7cc/mole for V at 25°C, pH 7.6. Comparable data at 2°Cindicate values of 5 kcal/mole for H. –13 kcal/mole forTS, and negligible V. According to the results of 25°C,Ca²⁺-activatkm of myosin-ATP may involve disruption of fouror five hydrophobic or polar groups, presumably due to an "opening-up"of the myosin molecule at or near the site for ATP binding.It would also appear that Coryphaenoides myosin has undergonean adaptive change in the enzyme mechanism for ATPase such thatthe rate of ATP hydrolysis is relatively insensitive to pressureand temperature under conditions encountered by the living fish.     

Molecular Phylogeny of Arthropods and the Significance of the Cambrian "Explosion" for Molecular Systematics

SYNOPSIS. Accurate phylogenetic reconstruction requires charactersystems that have evolved fast enough to have kept pace withcladogenesis but slowly enough to have conveyed the resultingphylogenetic signal to the present. Because stratigraphic evidencesuggests that basal arthropod lineages arose rapidly duringan ancient (Cambrian) phylogenetic radiation, the discoveryof molecular sequences capable of resolving arthropod phylogenymay be a significant challenge for molecular systematists. Thischallenge is exemplified by our attempt to resolve arthropodphylogeny using the amino acid sequence of elongation factor-1(EF-1). Our fossil-based assessment of evolutionary rates indicatesthat EF-la should be capable of resolving Cambrian-age divergences.However, phylogenetic analysis using EF-1 fails to establishrelationships among most higher-level groups, although it doesrecover more recently derived clades. Here we propose two modelsto explain this incongruity. The Rapid Radiation Model maintainsthat fossil-based estimates of arthropod diversification areessentially accurate and that diversification occurred so rapidlyduring the Cambrian that few phylogenetically significant changesoccurred in the slowly evolving EF-1 sequence. The EnhancedPreservation Model maintains that fossil-based estimates ofCambrian-age divergences reflect enhanced preservation of pre-existinglineages and that arthropod diversification occurred beforethe Cambrian. This model attributes lack of resolution to degradationof phylogenetic signal within EF-1 by subsequent evolution.Current evidence is more consistent with the Enhanced PreservationModel, which implies that fossil-based methods can be very misleadingwhen attempting to gauge the phylogenetic information contentof molecular sequences for Cambrian- and Precambrian-age divergences.     

Isolation of Subunits of Coupling Factor 1 from Maize and Spinach Chloroplasts and Properties of Combinations of Subunits with ATPase Activity

Subunits (, ß, ) and mixtures of subunits ( ß, , ß , ß ) were isolated without denaturationfrom a chloroform extract of chloroplast coupling factor 1 (CF₁)from maize (Zea mays var. Ushiku 5-4) and from spinach by fastprotein liquid chromatography (FPLC), on an anion-exchange columnof Mono-Q in the presence of n-octylglucoside (OG) and on achromatofocusing column of Mono-P. The ß -subunitcomplex (CF¹ ß ) was the minimum unit required forATPase activity, as was confirmed by the reconstituted complexof ß and subunits. An subunit isolated from maizeinhibited the ATPase activity of CF₁ ß from bothmaize and spinach. CF₁ ß was found to contain anOG-dependent Mg²⁺-ATPase. The ATPase activity of CF₁ ß required divalent cations, such as Mg²⁺ or Mn²⁺, for its expressionin the presence of OG; its optimum pH was 8.0 and it was markedlyinhibited by NaN₃. The enzyme hydrolyzed ATP in prefernece toGTP but not CTP, UTP, ADP, AMP or pNPP. Lineweaver-Burk plotsof its activity were curvilinear in the range of 0.6–0.7mM ATP.Mg²⁺. ¹Present address: Department of Biology, School of Education,Waseda University, Shinjuku-ku, Tokyo, 160 Japan. (Received February 15, 1989; Accepted April 20, 1989)     

Control of Tissue Specificity: The Pattern of Cellular Synthetic Activities in Tissue Transformation

During transformation of the dorsal marginal iris into lenstissue after removal of the lens in the adult newt, the cellsundergo gradual changes in synthetic activities. Autoradiographicdata indicate an enhancement of RNA synthesis in the nucleusof iris cells, which is followed by enhancement of protein synthesisand onset ot DNA synthesis. After discharge of pigment granulesand a period of cellular multiplication accompanied by ribosomeproduction, the cells stop DNA synthesis and start to show detectableamounts of lens-specific proteins (-,ß-, and -crystallins).This time coincides with initiation of differentiation of primarylens fibers. In the later stages of regeneration, - and ß-crystallinsare present in the dividing cells of the lens epithelium, aswell as in the cells of the fiber area, but -crystallins aredetected only in Che cells of the fiber area. The data wereinterpreted as suggesting that the gene utilization patterntypical for the iris is not directly converted into that forthe lens, but goes through intermediate patterns before thetissue transformation is completed.     

Regulation of Drosophila Visual System Development by Nitric Oxide and Cyclic GMP

Photoreceptors undergoing target selection in the optic lobeof Drosophila express a nitric oxide sensitive soluble guanylatecyclase (sGC). At the same time, cells in the target regionof the optic lobe express nitric oxide synthase (NOS). Pharmacologicalinhibition of NOS, NO or sGC leads to disruption of the retinalprojection pattern in vitro, and the extension of individualretinal axons beyond their appropriate targets. The disruptiveeffects of NOS inhibition in vitro are prevented by adding acGMP analog. Mutations in the sGC alpha subunit gene, Gc1, reducesGC expression and attenuate NO-sensitive retinal cGMP productionin the visual system. Although the retinal projection patternis undisturbed in Gc1 mutants, they lack positive phototaxisas adults, suggesting inappropriate connections exist betweenthe photoreceptors and optic lobe interneurons in these flies.Preliminary results show that heat-shock expression of wild-typeGc1 during metamorphosis can restore positive phototaxis insevere Gc1 mutants. These in vivo results support the in vitrofindings that NOS and sGC activity are required to promote theappropriate retinal innervation of the optic lobe.     

Molecular dynamics simulations of oligosaccharides and their conformation in the crystal structure of lectin-carbohydrate complex: importance of the torsion angle {psi} for the orientation of {alpha}1,6-arm

The conformation of the heptasaccharide Man-1,6-(Man-1,3)(Xyl-ß1,2)-Man-ß,4-GlcNAc₂-ß1,4-(L-Fuc-1,3)-GlcNAc₁,the carbohydrate moiety of Erythrina corallodendron lectin (EcorL),the hexasaccharide Man-1,6-(Man-1,3) (GlcNAc-ß1,4)-Man-ß1,4-GlcNAc-ß1,4-GlcNAcand their disaccharide fragments have been studied by moleculardynamics (MD) simulations for 1000 ps with different initialconformations. In the isolated heptasaccharide, the most frequentlyaccessed conformation during MD has a value of 180° aroundMan-1,6-Man linkage. This conformation is stabilized by theformation of a hydrogen bond between the carbonyl oxygen ofGlcNAc₂ with the O3/O4 hydroxyls of the 1,6-linked mannose residue.The conformation of the heptasaccharide found in the crystalstructure of the EcorL-lactose complex (Shaanan et al., Science,254, 862, 1991), that has a value of 76° around Man-1,6-Manlinkage, is accessed, although less frequently, during MD ofthe isolated oligosaccharide. The ,, = 58°,–134°,–60°conformation around Man-₁,6-Man fragment observed in the crystalstructure of the Lathyrus ochnrs lectin complexed with a biantennaryoctasaccharide (Table I in Homans,S.W., Glycobiology, 3, 551,1993) has also been accessed in the present MD simulations.These values for the 1,6-linkage, which are observed in theprotein-carbohydrate crystal structures and are accessed inthe MD simulations, though occasionally, have not been predictedfrom NMR studies. Furthermore, these different values of leadto significantly different orientations of the 1,6-arm for thesame value of . This contrasts with the earlier predictionsthat only different values of can bring about significant changesin the orientation of the ₁,6-arm. The MD simulations also showthat the effects of bisecting GlcNAc or ß1,2-xyloseare very similar on the ₁,3-arm and slightly different on the₁,6-arm. bisecting GlcNAc carbohydrates glycoprotein lectinsaccharide complex     

Pumpkin (Cucurbita sp.) seed globulin III. Comparison of subunit structures among seed globulins of various Cucurbita species and characterization of peptide components

Various Cucurbita seed globulins showed patterns similar toone another on SDS-gel electrophoresis, and ß bandsfor unreduced globulins and , ', and ' bands for reduced ones.On gel electrophoresis in 6 M urea, reduced globulin gave twoacidic and two basic bands. These corresponded to and ' chainsand ₁ and ₂ chains, respectively, identified by two-dimensionalurea-SDS gel electrophoresis. The compositions of the and ßsubunits were proposed. (Received September 8, 1977; )     

Hydrophobic mannosides act as acceptors for trypanosome {alpha}-mannosyltransferases

A series of hydrophobic mannosides were synthesized and testedfor their ability to act as acceptor substrates for mannosyltransferasesin a Trypanosoma brucei cell-free system. The thiooctyl -mannosidesand octyl -mannosides all accepted single mannose residues in-linkage, as judged by thin layer chromatography of the productsbefore and after jack bean -mannosidase digestion. The mannosylationreactions were inhibited by amphomycin, suggesting that theimmediate donor was dolicholphosphate-mannose (Dol-P-Man) inall cases. The transferred -mannose residues were shown to beboth 1-2 and 1-6 linked by Aspergillus phoenicis -mannosidaseand acetolysis treatments, respectively. These data suggestthat the compounds can act as acceptor substrates for the Dol-P-Mandependent 1-2 and 1-6 mannosyltransferases of the GPI biosyntheticpathway and/or the dolichol-cycle of protein N-glycosylation.One of the compounds, Man1-6Man1-O-(CH₂)₇CH₃, inhibited endogenousGPI biosynthesis in the cell-free system, suggesting that itcould be a substrate for the trypanosome Dol-P-Man:Man₂GlcN-Pl1-2 mannosyltransferase. dolichol glycosylphosphatidylinositol mannosyltransferase trypanosome     

Temperature-Dependent Inhibitive Actions of {alpha},{alpha}'-Dipyridyl and Cycloheximide on the Senescence of Maize Leaves

Temperature-dependent inhibitive actions of ,'-dipyridyl andcycloheximide on the senescence of maize leaves were studied.,'-Dipyridyl effectively inhibited the loss of chlorophyll at25?C but not at 35?C. Gycloheximide was highly effective inpreserving chlorophyll at both of 25 and 35?C. Spectral analysisof senescent leaves at 35?C in ,'-dipyridyl showed simultaneousbleaching the carotenoid and chlorophyll. (Received February 20, 1984; Accepted June 14, 1984)     

An Assessment of Gibberellin Structure-activity Relationships

Information on the biological activities of gibberellins (GAs)in the barley aleurone, Tangin-bozu dwarf rice, dwarf pea, lettucehypocotyl and cucumber hypocotyl bioassays is reviewed and discussedin the context of GA structure-activity relationships. The barley aleurone bioassay exhibits a limited response toGAs and it is suggested that this may be because the aleuronecells are able to carry out few GA interconversions. Consequentlyactivity is determined by the degree of compatibility betweenthe GAs and a receptor site. In this assay high biological activityis associated with GAs having a 3ß-hydroxy--lactonestructure. This activity is substantially enhanced by the additionalpresence of a 13-hydroxyl group. The substitution of a -lactoneor a -lactol for a -lactone results in reduced activity while3ß,13-dihydroxy GAs with either 20-carboxyl or 20-methylfunctions are completely inactive. The Tanginbozu dwarf ricebioassay responds to many more GAs than the barley aleuronesystem possibly because the rice seedlings can carry out extensiveGA interconversions. Under these circumstances GAs that areinactive per se can be metabolically converted to active forms.There is no interaction between the 3ß- and 13-hydroxyfunctions of GA molecules in the rice assay. Activity appearsto be determined by the degree oxidation of the C-20 group.The order of activity is usually -lactone > -lactol >-lactone > methyl > carboxyl. It is suggested this mayindicate that in rice seedlings C₂₀-GAs are converted to C₁₉-GAsvia a Baeyer-Villiger type oxidation. Activity in the dwarfpea bioassay is dependent upon GAs possessing both 3ß-and 13-hydroxyl groups and is again related to the state ofoxidation at the C-20 locus. In the lettuce bioassay activityis restricted to GAs with a -lactone function. In some instancesa -lactone, but not a -lactol, can substitute effectively. Thismay imply that the applied C₂₀-GAs are not converted to C₁₉-GAsand that the response to the -lactone results from the six-memberedring mimicking the -lactone at the receptor site. Only GAs havinga 19,10 or a 19,20 lactonic bridge show substantial activityin the cucumber bioassay. The additional presence of eithera 12- or a 13-hydroxyl group severely reduces activity.     

Glycosidases in Carrot Cells in Suspension Culture: Localization and Activity Change during Growth

Localization of four glycosidases, -galactosidase (-Gal), ß-galactosidase(ß-Gal), -glucosidase (-Glu) and ß-glucosidase(ß-Glu) in suspension-cultured carrot cells was studied.Wall-bound enzymes were made soluble when the cells were convertedto protoplasts by cellulase and pectinase. -Gal was separatedinto two forms, designated I and II, by chromatography on aSephadex G-200 colunm. -Gal I was located exclusively in thecytoplasm whereas -Gal II was found in both the cytoplasmicand cellwall fractions. The pH optimum was in the neutral regionfor -Gal I and in the acidic region for the other glycosidases,including -Gal II. Both intact cells and protoplasts in suspensionculture secreted these glycosidases, except -Gal I, into themedium. Specific activities of the glycosidases, especiallythe activity of ß-Gal, decreased in the early logarithmicgrowth phase and increased as cells went through late logarithmicand stationary phases. In protoplast culture, glycosidase activitygradually increased as cell wall regeneration proceeded. (Received December 13, 1980; Accepted February 10, 1981)     

Mechanical Design of Fiber-Wound Hydraulic Skeletons: The Stiffening and Straightening of Embryonic Notochords

The notochord can play an important mechanical role in shapechanges during early morphogenesis of vertebrates. For example,osmotic inflation of notochords elongates and straightens theaxis of frog early tail-bud embryos. In Xenopus laevis, thesheath of cross-helically arranged fibers around the notochordlimits the shape changes it undergoes when inflating, causingthe notochord to stiffen and straighten (Adams et al., 1990;Koehl et al., 1990). We used physical models of stage 24 X.laevis notochords to explore the mechanical consequences ofdifferent arrangements of the sheath fibers on the behaviorof such curved hydraulic cylinders. All the models straightenedupon inflation regardless of initial fiber angle ( = angle ofthe fibers to long axis of the cylinder). Notochord models with > 54° lengthened and narrowed as they straightened;although they could push, the forces they exerted were limitedby their tendency to buckle, which increased the greater the. In contrast, models with < 54° shortened and widenedas they straightened and showed pronounced increases in flexuralstiffness. The mean of X. laevis early tail-bud notochordsis 54°, a fiber angle that permits an increase in the end-to-enddistance of the model (along the anterior-posterior axis ofthe embryo) as it straightens and pushes when pressurized, butthat is less prone to Euler and local buckling than are modelswith higher 's. Nonetheless, a of 54° in notochords maysimply be the result of osmotic swelling.     

Sialylation of n-alkyllactosides, galactosides and glucosides by sialyltransferases from rat liver Golgi vesicles

nAlkyl - and -lactosides, galactosides and glucosides with differentalkyl chain lengths (C₂, C₈, C₁₄, and C₂₀) were synthesizedand used as acceptors for sialyltransferases from rat liverGolgi vesicles. The -galactosides, -glucosides, and both - and-lactosides, were sialylated. Keeping the acceptor concentrationconstant, sialylation rates reached a maximum for the n-octyl- and -lactosides, n-Octyl -galactoside and noctyl -glucoside,respectively. noctyl -glucoside, respectivwly. n-Octyl -galactosideand n-octyl -glucoside were not sialylated. The reaction productswere characterized by TLC. With n-octyl lactoside and galactosideas acceptors, two major sialylation products were formed. Thjeycould be separated by preparative TLC, and their structureswere identified as 2–3 and 2–6 sialylated acceptors,respectively, by a combination of periodated oxidation, NaBD₄reduction,permethylation and subsequent analysis by fast atombombardment mass spectrometry (FAB-MS). The structure of thesingle product obtained from n-ictyl -glucoside was determinedto be the 2–6 sialylated glucoside. Competition experimentswith n-octyl lactoside and lactosylceramide and gangliosideGal1-3GalNAc1-4(NeuAc2–3)Gal1–4Glcbeeta1–1Cer(GM1) as acceptors for sialyltransferases suggested that SAT-I[NeuAc2–3Gal1–4Glc1-1Cer (GM3) synthase] was atleast in least in part responsible for the 2–3 sialylationof n-octyl lactoside. alkylgalactosides alkylglucosides alkyllactosides neoglycolipids sialytransferases     

Regulation of sexual agglutinability in Saccharomyces cerevisiae of {alpha} and {alpha} types by sex-specific factors produced by their respective opposite mating types

The sexual agglutinability of haploid cells of heterothallicSaccharomyces cerevisiae was repressed when they were culturedin the absence of easily fermentable sugars, such as glucoseand mannose. The repression was reversed by the action of hormone-likesubstances of the opposite mating types. The substance producedby mating type cells was identical to subtsance-I which isknown to induce sexual agglutinability of inducible matingtype cells. The mating type cells produce a new hormone-likesubstance which induces or enhances sexual agglutinability of mating type cells. A crude fraction of the mating type-specific substance ( substance-I)was obtained by passing the culture filtrate of mating typecells through Amberlite CG-50 (H⁺ form), followed by elutionwith 1.5 M ammonia. ² On leave from Osaka City University. (Received December 25, 1975; )