Published by De Gruyter

Volume 54 Issue 3-4

Issue of Zeitschrift für Naturforschung C

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Journal Overview

Open Access June 2, 2014

Prenylated Bibenzyls from the Liverwort Radula laxiramea

Frank Cullmann, Hans Becker

Page range: 147-150

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Abstract

From Radula laxiramea, 12 bibenzyl derivatives and the common bisbibenzyl perrottetin E were isolated. Two compounds are described for the first time as natural products, and one, previously only known after derivatisation, was found in genuine form . Perrottetinene, a cannabinoid from a liverwort is worth mentioning.

Open Access June 2, 2014

Sesquiterpenoids from the Liverwort Porella canariensis

Frank Cullmann, Hans Becker

Page range: 151-155

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Abstract

From the liverwort Porella canariensis, collected in Madeira, Portugal, nine pinguisanes, four drimanes, including the pungent polygodial, two germacranes, and two aromadendranes were isolated. The major compounds were the arom adendrane ent-cyclocolorenone and the nor-pinguisane norpinguisone. Three hydrocarbons were isolated by low temperature column chrom atography. One germacrane and one pinguisane proved to be new natural products.

Open Access June 2, 2014

A Pyoverdin from the Antarctica Strain 51W of Pseudomonas fluorescens

Jessica Voss, Kambiz Taraz, Herbert Budzikiewicz

Page range: 156-162

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Abstract

From the strain 51W of Pseudomonas fluorescens living under extreme conditions at the Schirmacher Oasis (Antarctica) a pyoverdin was obtained. Its structure was elucidated by chemical degradation and spectroscopic methods. The NMR data of the pyoverdin and of its Ga(III) complex were compared. Appreciable influences of the metal on the chemical shifts of the atoms at its binding sites were observed. Thus the structural elements involved in the complexation can be identified and coinciding signals of amino acids occurring more than once in the peptide chain can be separated.

Open Access June 2, 2014

Noroudemansin A, a New Antifungal Antibiotic from Pterula Species 82168 and Three Semisynthetic Derivatives

Michaela Engler-Lohr, Timm Anke, Veronika Hellwig, Wolfgang Steglich

Page range: 163-168

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Abstract

A new antifungal (E)-β-methoxyacrylate, noroudemansin A (1), was isolated from cultures of Pterula sp. 82168. Its biological activities were investigated and compared with oudemansin A. The structure was elucidated by spectroscopic methods. Three semisynthetic noroudemansin A derivatives were synthesized from the natural product.

Open Access June 2, 2014

Antibacterial Activity of Simple Coumarins: Structural Requirements for Biological Activity

Oliver Kayser, Herbert Kolodziej

Page range: 169-174

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Abstract

The antibacterial activity of a series of simple coumarins was evaluated against 8 microorganisms, including three Gram-positive (Staphylococcus aureus, beta-hemolytic Streptococcus and Streptococcus pneumoniae) and five Gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus mirabilis and Haemophilus influenzae), using the microdilution broth method. The coumarins tested showed broad diversity regarding growth inhibitory activity with minimum inhibitory concentrations ranging from 0.9 to >12.4 μᴍ. This study, presenting the first systematic analysis of structure-activity relationships among this group of coumarins, revealed some interesting structural requirements. While coumarins with a methoxy function at C-7 and, if present, an OH group at either the C-6 or C-8 position are invariably effective against the spectrum of tested standard bacteria (Gram-negative microorganisms including the Gram-positive bacterium Staphylococcus aureus), the presence of an aromatic dimethoxy arrangement is apparently favourable against those microorganisms which require special growth factors (beta-hemolytic Streptococcus, Streptococcus pneumoniae and Haemophilus influenzae). A combination of these structural features, two methoxy functions and at least one additional phenolic group as reflected by the highly oxygenated coumarins, identify promising candidates with antibacterial broad-spectrum activity.

Open Access June 2, 2014

Structure Elucidation of a Purple Peptide Found During the Purification of a Recombinant Protein from Escherichia coli

Andrew W. Guzzetta, Pamela Clark, Robert Tappe, Herbert Budzikiewicz

Page range: 175-180

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Abstract

A purple substance (4) partially co-purified with a recombinant human B-type natriuretic peptide (hBNP), following an E. coli fermentation. The structure of the compound was elucidated by NMR, electrospray and FAB mass spectrometry. The chromophore is a 1,4-naphthoquinone condensed with the N-terminal cysteine of a heptapeptide by its NH 2 - and SH-groups to form a dihydro-thiazine ring. The peptide sequence was determined as Cys-Lys-Val-Leu-Arg-Arg-His by mass spectrometric techniques. CID and data base matching identified it as the C-terminus of the 32-amino-acid recombinant peptide hBNP. This modification of an N-terminal Cys may be a more general phenomenon with implications for the production of heterologous proteins by microorganisms.

Open Access June 2, 2014

Purification and Characterization of a β-Glucosidase Specific for 2,4-Dihydroxy- 7-methoxy-1,4-benzoxazin-3-one (DIMBOA) Glucoside in Maize

Akira Oikawa, Kenkichi Ebisui, Masayuki Sue, Atsushi Ishihara, Hajime Iwamura

Page range: 181-185

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Abstract

Occurrence and properties of hydroxamic acid glucoside glucosidase were investigated in 10-day-old, autotrophic maize (Zea mays L.) in which 2,4-dihydroxy-7-methoxy-1,4- benzoxazin-3-one glucoside (DIMBOA-G) is a major benzoxazinone component. Crude extracts of both leaves and roots showed glucosidase activity for both DIMBOA-G and 2,4- dihydroxy-1,4-benzoxazin-3-one glucoside (DIBOA-G). A cation-exchange chromatography after cryoprecipitation of the extract from leaves gave a peak with both activities, and further purification by ion-exchange and hydroxyapatite chromatography gave a fraction with an apparent homogeneity, the purification being 560 fold. The K m values (mᴍ) of the purified glucosidase were 0.16 for DIMBOA-G, 0.68 for DIBOA-G and 2.96 for p-nitrophenyl-β-ᴅ-glucopyranoside. The activity on salicin and esculin was too low to be detected. The data indicate that a glucosidase specific for DIMBOA-G comes into contact with constitutive benzoxazinone glucosides producing defensive aglycone when plants are damaged by microbial or insect attacks.

Open Access June 2, 2014

Effects of Trehalose and Ethanol on Yeast Cytosolic Pyrophosphatase

Dahabada Helena José Lopes, José Roberto Meyer-Fernandes, Mauro Sola-Penna

Page range: 186-190

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Abstract

Trehalose has been described to protect several enzymes against destabilizing conditions. This sugar is naturally accumulated by yeast as a stress protectant. A common stress condition that yeast is normally submitted is the presence of ethanol, the by-product of fermentation process of several yeast. In this paper we show the effects of trehalose and ethanol, alone or together, on yeast pyrophosphatase, and the effects of these compounds on inhibition and unfolding of pyrophosphatase promoted by urea. We show that both trehalose and ethanol inhibit pyrophosphatase in a dose-dependent manner, and that the presence of ethanol does not modify the inhibition promoted by trehalose as well as the presence of trehalose does not modify the inhibition promoted by ethanol. The effects of trehalose on pyrophosphatase are completely reversible, but the inhibition caused by ethanol was only partially reversible. Incubation of pyrophosphatase with 10% (v/v) ethanol promoted an inhibition of 15%, and the control activity was completely recovered after removal of ethanol. On the other hand, when pyrophosphatase was incubated with 20% (v/v) ethanol an inhibition of 40% of the control activity was observed which persisted after removal of ethanol. Ethanol also potentiates the inhibition of pyrophosphatase promoted by urea, and contributes for an irreversible inactivation and unfolding of pyrophosphatase in the presence of urea. Trehalose, that protects this enzyme against the inhibition and unfolding promoted by the chaotropic compound urea, was inefficient to protect against the effects of ethanol. Trehalose was also efficient to prevent an irreversible inactivation induced by urea.

Open Access June 2, 2014

Physiological Significance of Overproduced Carotenoids in Transformants of the Cyanobacterium Synechococcus PCC7942

Navassard V. Karapetyan, Ute Windhövel, Alfred R. Holzwarth, Peter Böger

Page range: 191-198

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Abstract

The functional location of carotenoids in the photosynthetic apparatus of -crtB and -pys transformants of the cyanobacterium Synechococcus PCC7942 was studied and compared with a control strain -pFP 1-3. These transformants overproduce carotenoids due to the insertion of an additional foreign phytoene synthase gene. A higher carotenoid content was found for -crtB and -pys transformants both in whole cells and isolated membranes; the -crtB transformant was also enriched with chlorophyll. 77-K fluorescence emission and excitation spectra of the phycobilin-free membranes were examined for a possible location of overproduced carotenoids in pigment-protein complexes in situ. A similar ratio of the amplitudes of fluorescence bands at 716 and 695 nm emitted by photosystems I and II, found for the three strains, indicates that the stoichiometry between photosystems of the transformants was not changed. Overproduced carotenoids are not located in the core antenna of photosys tem I, since 77-K fluorescence excitation spectra for photosystem I of isolated membranes from the studied strains do not differ in the region of carotenoid absorption. When illuminated with light of the same intensity but different quality, absorbed preferentially by either carotenoids, chlorophylls or phycobilins, respectively, oxygen evolution was found always higher in the transformants -crtB and -pys than in -pFP 1-3 control cells. Identical kinetics of fluorescence induction of all strains under carotenoid excitation did not reveal a higher activity of photosystem II in cells enriched with carotenoids. It is suggested that overproduced carotenoids of the transformants are not involved in photosynthetic light-harvesting; rather they may serve to protect the cells and its membranes against photodestruction.

Open Access June 2, 2014

Comparative Immunological and Chemical Analysis of Lipids and Carotenoids of the D1-Peptide and of the Light-Harvesting-Complex of Photosystem II of Nicotiana tabacum

Anette Gasser, Stefan Raddatz, Alfons Radunz, Georg H. Schmid

Page range: 199-208

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Abstract

The light-harvesting-complex (LHCP) was isolated from photosystem II of Nicotiana tabacum var. John William’s Broadleaf by means of the detergent acetyl-β-ᴅ-glucopyranoside and fractionating centrifugation. The D1-peptide of photosystem II was isolated as a dimer with the molecular mass of 66 kDa from the chlorophyll-deficient tobacco mutant N. tabacum Su/su by means of sodium dodecyl sulfate polyacrylamide gel electrophoresis. Both preparations were characterized by means of the Western blot procedure using monospecific antisera to the proteins of photosystem II and monospecific antisera to lipids with which the lipids bound to peptides were determined. In parallel to this, lipids bound to the isolated LHCP-complex and to the isolated D1-peptide were determined by lipido-chemical methods. The extraction of the isolated core peptide D1 with a mixture of boiling methanol and chloroform and subsequent HPLC-chromatography showed that in the D1-peptide isolated via SDS-polyacrylamide gel electrophoresis, monogalactolipids, phosphatidylglycerol and sulfolipid molecules are bound in the molar ratio 1:3:17. By means of the immunological procedure of Western blotting we were able to show that the 66 kDa band of the isolated dimeric D1 reacts positively only with the antisera to monogalactolipid, sulfolipid, β-carotene and violaxanthin. With the antiserum to digalactolipid and that to phosphatidylglycerol a positive reaction is only observed if the preparation used in the Western blot is not the isolated D1-peptide but a ‘‘total” photosystem Il-preparation. The lipid extraction of the LHCP-complex and the subsequent analysis by thin-layer chromatography led to the result that the isolated LHCP-complex contained in bound form 3 molecules monogalactolipid, 1 molecule of digalactolipid, 1 molecule of phosphatidylglycerol and 1 molecule of lutein. Less than 1 molecule of sulfolipid, β-carotene, neoxanthin and violaxanthin are found. In the Western blot analysis only the antiserum to monogalactolipid and phosphatidylglycerol and among the carotenoid antisera only the antisera to β-carotene, violaxanthin and to neoxanthin reacted. With the antisera to the digalactolipid, to the sulfolipid and the antisera to the xanthophylls, namely to lutein and neoxanthin, a positive reaction occurred only if the material used in the Western Blot was the “total” photosystem Il-preparation. By gas chromatography of the fatty acids of the isolated peptide fractions it was shown that, compared to the lipids of photosystem II and of the thylakoid membrane, in lipids of the isolated D1-peptide and of the LHCP-complex the saturation degree of fatty acids is strongly increased. Whereas palmitic acid in chloroplast lipids makes up for only 11% of the fatty acids, this saturated fatty acid increases in the lipids of the LHCP to 20% and makes up for 74% of total fatty acids in the lipids of the D1-peptide. Linoleic and linolenic acids are completely absent and oleic acid makes up for 14% of total fatty acids. In contrast to the lipids of the thylakoid membrane, the lipids bound to proteins/peptides are characterized by a strongly saturated character.

Open Access June 2, 2014

Oxygen Uptake during Photosynthesis of Isolated Pea Chloroplasts

Norbert Grotjohann, David Messdaghi, Wolfgang Kowallik

Page range: 209-219

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Abstract

Mass spectrometric analysis of the gas exchange of illuminated leaflets of 10-14 d old pea seedlings revealed not only 16 O 2 -liberation from photosynthetic H 2 16 O-splitting, but also uptake of 18 O 2 , applied to the gas phase of the reaction vessel. Isolated intact chloroplasts of such leaflets suspended in a medium containing NaHCO 3 and glycerate 3-phosphate, on irradiation with blue (λ 448 nm) or red (λ 679 nm) light also produced 16 O 2 from water oxidation and consumed 18 O 2 from the gas phase. The two reactions were saturated at the same quantum fluence rates. Uptake of 18 oxygen was not affected by inhibitors of mitochondrial respiration (alternative pathway included), such as rotenone (5 x l0 -5 ᴍ), antimycin A (5 x l0 -6 ᴍ), KCN (10 -3 ᴍ), SHAM (10 -3 ᴍ), or propylgallate (10 -3 ᴍ). It was, however, absent, when photosynthetic 16 oxygen evolution was completely inhibited by DCMU (10 -5 ᴍ). DBMIB (10 -5 ᴍ), assumed to prevent electron flow from plastoquinone pool to the cytochrome b 6 /f-complex, suppressed photosynthetic oxygen evolution, but did not impair uptake of 18 O 2 . A similar result was obtained at application of 4 x l0 -5 ᴍ antimycin A. The data are interpreted to show a drain off to molecular oxygen of light-excited electrons from the photosynthetic electron transport chain at the site of plastoquinone pool during photosynthesis. This corresponds to chlororespiration, originally described for Chlamydomonas in darkness by Bennoun (1982). It is discussed, whether O 2 -uptake during photosynthesis is an additional means for providing ATP for photosynthetic CO 2 -reduction by increasing the proton gradient across the thylakoid membrane.

Open Access June 2, 2014

Grapevine Protoplasts as a Transient Expression System for Comparison of Stilbene Synthase Genes Containing cGMP-Responsive Promoter Elements

Ilka Brehm, Regina Preisig-Müller, Helmut Kindl

Page range: 220-229

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Abstract

A method for preparing elicitor-responsive protoplasts from grapevine cells kept in suspension culture was established. The protoplasts were employed in order to perform transient gene expression experiments produced by externally added plasmids. Using the gene coding for bacterial β-glucuronidase as the reporter gene, the transient expression under the control of various promoters of stilbene synthase genes were analyzed. The elicitor-responsiveness of promoters from grapevine genes and heterologous promoters were assayed: the grapevine stilbene synthase gene VST-1 and pine stilbene synthase genes PST-1, PST-2 and PST-3. Compared to the expression effected by the cauliflower mosaic virus 35S RNA-promoter, the stilbene synthase promoters caused a 2-5-fold increase in GUS-activity. Incubation of transformed protoplasts with fungal cell wall further stimulated the stilbene synthase promoters but not the 35S RNA-promoter. An even more pronounced differentiation between the promoters was observed when cGMP was included in the transient expression assays. Instead of treating transformed protoplasts with fungal cell wall we administered simultaneously cGMP and the plasmid to be tested. The cGMP-responsive increase was (a) specific concerning the nucleotide applied, (b) characteristic of grapevine protoplasts, and (c) not seen with shortened promoter-GUS constructs or GUS under the control of the 35S RNA-promoter. The highest cGMP-dependent reponse to stress was shown by the promoter of the grapevine stilbene synthase gene VST-1.

Open Access June 2, 2014

Heterologous Overexpression of Membrane-Anchored Subunit II of Spinach Chloroplast ATP Synthase and Its Detergent-Free Purification as a Soluble Protein

Hans-Jürgen Tiburzy, Martin Zimmermann, Regina Oworah-Nkruma, Richard J. Berzborn

Page range: 230-238

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Abstract

Subunit II is one of the four nonidentical subunits of the membrane integral, protontransporting moiety (CFₒ) hloroplast ATP synthase. In chloroplasts of spinach leaves, it is the only nuclear-encoded CFₒ subunit. It has been deduced that CFₒII is not an additional subunit typical for photosynthetic organisms with no counterpart in E.coli, but equivalent to E. coli subunit b (Tiburzy, H.-J. and Berzborn, R. J. (1997), Z. Naturforsch. 52c, 789-798). Heterologous expression of subunit II was achieved by using the bacterial expression vector pT7-7. Recombinant subunit II (II rec ) does not integrate into the bacterial membrane nor does it precipitate into inclusion bodies. Gel filtration chromatography indicates that II rec forms higher order aggregates. In three chromatographic steps approx. 10 mg of soluble II rec of electrophoretic homogeneity are obtained from one liter of bacterial culture without using detergents. Thus, a eukaryotic membrane-anchored protein has been overexpressed in E. coli and has been purified in a soluble form.

Open Access June 2, 2014

Theoretical Description of the Coding Potential of Diamino-5-formamidopyrimidines

Piotr Cysewski, Ryszard Oliński

Page range: 239-245

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Abstract

The results of geometry optimisation of possible Watson-Crick-like pairs o f 2,6-diamino-4-oxy-5-formamidopyrimidine (fapy-adenine) or 4,6-diamino-5-formamidopyrimidine (fapy-guanine) were presented. In the absence of the external field the fapy-adenine is able to form pairs with all four canonical nucleic acid bases. However, pairs with guanine, cytosine and thymine the most stable are. Thus, the potential miscoding abilities may be observed. In contrast, in the presence of the external field the mispairing abilities of fapy-adenine become insignificant since the most stable dimers are formed with thymine. The pairing properties of fapy-guanine are complex and depend on its tatomeric form. In the absence of an external field the 4-enol-6-keto-diamino tautomer of fapyG is able to form stable dimers with thymine and cytosine, while the 4,6-diketo-diamino tautomer forms the most stable pairs with cytosine and guanine. The presence of the water solvent does not significantly alter the pairing abilities of fapy-guanine. However, pairs with thymine are at least as stable as the Watson-Crick GC pair. Thus, in polar conditions the mispairing potential of fapyG will be extended and may be enriched by potential GC → AT transition.

Open Access June 2, 2014

Bromoisoxazoline Alkaloids from the Caribbean Sponge Aplysina insularis

Thomas Fendert, Victor Wray, Rob W. M. van Soest, Peter Proksch

Page range: 246-252

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Abstract

An investigation of a specimen of the Caribbean sponge Aplysina insularis resulted in the isolation of fourteen bromoisoxazoline alkaloids (1 - 14), of which 14-oxo-aerophobin-2 (1)* is a novel derivative. Structure elucidation of the compounds have been established from spectral studies and data for 1 are reported. Constituents 2 to 6 and 11 to 14 have not been identified sofar in Aplysina insularis species. The presence of the known compounds 7 to 9 in Aplysina insularis indicates that their use for chemotaxonomical purposes is questionable.

Open Access June 2, 2014

New Sex Attractants for Five Chamaesphecia Species (Lepidoptera, Sesiidae) from the Ukraine and Turkmenistan

Raimondas Mozūraitis, Vincas Būda, Jan Metleuski

Page range: 253-258

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Abstract

Field screening tests of (3Z,13Z)- and (3E,13Z)-octadecadienols, (2Z,13Z)-and (2E,13Z)-octadecadienols and their acetates as well as some binary mixtures of these compounds in dosages of 0.5 mg/dispenser were carried out in the Crimea, the Ukraine, and in the West Kopetdag mountains, Turkmenistan, in 1989-1993. New sex attractants for five clearwing moth species of the genus Chamaesphecia (Lepidoptera, Sesiidae) were discovered. Males of Ch. chalciformis were attracted by a 1:1 mixture of 3Z,13Z-18:OH and 2E,13Z-18:OAc, Ch. schmidtiformis by a 9:1 mixture of 3Z,13Z-18:OAc and 3Z,13Z-18:OH in the Ukraine as well as in the ratios 9:1 and 1:1 in Turkmenistan, Ch. mezentzevi by a 9:1 mixture of 3Z,13Z-18:OAc and the corresponding alcohol, Ch. zimmermanni by a 1:9 mixture of 3Z,13Z-18:OAc and 3.E,13Z-18:OH, and Ch. specia nova in Turkmenistan by a 1:1 mixture of 3Z,13Z-18:OH and 3E,13Z-18:OAc. Two inhibitors, 3Z,13Z-18:OH and 3E,13Z-18:OAc, of the sex attractant were found for Ch. zimmermanni. The periods of attraction to the traps were registered for males of Ch. zimmermanni and Ch. specia nova and were found to occur at 19 00 -21 00 and 14 30 -17 00 local time, respectively. Males of Ch. chalciformis and Ch. schmidtiform is were attracted to the traps in the afternoon.

Open Access June 2, 2014

Isolation and Identification of Peptidic α-Glucosidase Inhibitors Derived from Sardine Muscle Hydrolyzate

Toshiro Matsui, Tomoyuki Oki, Yutaka Osajima

Page range: 259-263

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Abstract

We report here the isolation of a-glucosidase (AGH) inhibitory peptides derived from sardine muscle hydrolyzate, which was prepared by digestion with Bacillus licheniformis alkaline protease. As a result of reversed-phase HPLC purification, two AGH inhibitory peptides were isolated from a DEAE -Sephadex A-25 column eluate. The peptides were identified as follows: Val-Trp (IC 50 = 22.6 mᴍ) and Try -Tyr -Pro -Leu (IC 50 = 3.7 mᴍ). AGH inhibitory studies of Try -Tyr -Pro -Leu and its derivatives demonstrated the importance of the tri-peptide chain length as well as the hydrophobic aromatic amino acid tyrosine at the N-terminus, aliphatic amino acids at the C-terminus, as well as an amide proton from the peptide chain at the middle position of the tri-peptide to develop AGH inhibition activity.

Open Access June 2, 2014

Solvent Accessibility to Aspartyl and Succinimidyl Residues at Positions 7 and 23 in the Amyloid β 1 - 28 Peptide

Roberto D. Lins, Thereza A. Soares, Ricardo Ferreira, Ricardo L. Longo

Page range: 264-270

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Abstract

The water accessibilities to aspartyl residues at positions 7 and 23 in the amyloid β 1–28 peptide associated with Alzheim er's Disease have been calculated using different techniques. These accessibilities of water were compared to those of the succinimidyl residues (SUC) replacing the aspartyl ones (ASP). It has been possible to ascertain that these modifications (A SP → SUC) lead to a significant increase in the water accessibility to the backbone and a-carbon atom of the SUC7 and SUC23 residues. It is suggested that the spontaneous trans formation of ASP → SUC might lead to an increase of the racemization rates due to the higher accessibility of water at these sites. It is also proposed that the behavior of the adjacent residues in the selectivity of the racemization is to control the water accessibility at the reactive residue.

Open Access June 2, 2014

The Anticancer Drug Adriamycin Interacts with the Human Erythrocyte Membrane

Mario Suwalsky, Pedro Hernández, Fernando Villena, Felipe Aguilar, Carlos P. Sotomayor

Page range: 271-277

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Abstract

Adriamycin, Anticancer Drug, Erythrocyte Membrane, Phospholipid Bilayer Adriamycin is an aminoglycosidic anthracycline antibiotic widely used in the treatment of cancer. Increasing reports point to the involvement of cell membranes in its mechanism of action. The interaction of adriamycin with human erythrocytes was investigated in order to determine the membrane binding sites and the resultant structural perturbation. Electron microscopy revealed that red cells incubated with the therapeutical concentration of the drug in human plasma changed their discoid shape to both stomatocytes and echinocytes. According to the bilayer couple hypothesis, this means that adriamycin was incorporated into either the inner or outer leaflets of the erythrocyte membrane. To explain this unusual result, the drug was incubated with molecular models. One of them consisted of dimyristoylphosphati-dylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) multilayers, representative of phospholipid classes located in the outer and inner leaflets of the erythrocyte membrane, respectively. X-ray diffraction showed that adriamycin interaction perturbed the polar head and acyl chain regions of both lipids. Fluorescence spectroscopy on another model, consisting of DMPC large unilamellar vesicles (LUV), confirmed the X-ray results in that adriamycin fluidized its hydrophobic moiety. It is concluded that adriamycin incorporates into both erythrocyte leaflets affecting its membrane structure.

Open Access June 2, 2014

Fluorescence Studies on Association of Human Translation Initiation Factor eIF4E with mRNA cap-Analogues

Zbigniew Wieczorek, Anna Niedźwiecka-Kornaś, Lidia Chlebicka, Marzena Jankowska, Katarzyna Kiraga, Janusz Stępiński, Michał Dadlez, Regina Drabent, Edward Darżynkiewicz, Ryszard Stolarski

Page range: 278-284

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Abstract

Binding of a long series of mono- and dinucleotide analogues of the 7-methylguanosine containing 5′-mRNA-cap to human protein translation initiation factor eIF4E has been investigated by means of fluorescence. A new methodological approach in gathering and analysis of the fluorescence data provided us with very accurate values of the association equilibrium constant K and normalized, maximal quenching of the protein fluorescence ΔF max , during titration of eIF4E by various cap-analogues. The results confirm participation of at least two conserved tryptophan residues of eIF4E in interaction with 7-methylguanine, as has been described recently for murine eIF4E, complexed with 7-methyl-GDP in crystal (Marcotrigiano et al., 1997, Cell 89, 951), and for yeast eIF4E, complexed with the same ligand in solution (Matsuo et al., 1997, Nature Struct. Biol. 4, 717). On the other hand binding by eIF4E of unmethylated guanine nucleotides and N 2 ,N 2 ,7-trimethylguanine containing nucleotides differ substantially from the way of binding of the regular mRNA-cap. Influence of the structural features of the cap-analogues, especially the type of the second nucleoside in the dinucleotide caps, on their association with eIF4E and biological activities in in vitro protein translation systems has been discussed in light of the known structures of the eIF4E -7- methyl-GDP complexes in crystal and solution.

Open Access June 2, 2014

Mitogen-Activated Protein Kinase and Cell Cycle Progression During Mouse Egg Activation Induced by Various Stimuli

Q. Y. Sun, Y. Lax, S. Rubinstein, D. Y. Chen, H. Breitbart

Page range: 285-294

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Abstract

A very sensitive method was established for detecting the activity of mitogen-activated protein (MAP) kinase in mouse eggs, and used to follow temporal changes of this kinase during fertilization and sponatenous or chemically-induced parthenogenic activation. MAP kinase activity increased between 1 and 2.5 h post-insemination, at which time the second polar body was emitted and sperm chromatin was dispersed; its activity decreased sharply at 8 h, when pronuclei were formed. Both calcium ionophore A23187 and ethanol simulta neously induced pronuclear formation and MAP kinase inactivation in aged eggs 8 h after incubation but less effectively in fresh eggs. The protein kinase inhibitor staurosporine induced pronuclear formation and MAP kinase inactivation more quickly than other treat ments, with MAP kinase inactivation occurring slightly proceeding pronuclear formation. Okadaic acid, a specific inhibitor of protein phosphatase 1 and 2A , induced increase in MAP kinase activity, and overcame pronuclear formation induced by various stimuli. MAP kinase inactivation preceded pronuclear formation in eggs spontaneously activated by aging in vitro, perhaps due to cytoplasmic degeneration and thus delayed response of nuclear envelope precursors to MAP kinase inactivation. These data suggest that MAP kinase is a key protein kinase regulating the events of mouse egg activation. Increased MAP kinase activity is temporally correlated with the second polar body emission and sperm chromatin decondensation. Although different stimuli (including sperm) may initially act through different mechanisms, they finally inactivate MAP kinase, probably by allowing the action of protein phosphatase, and thus induces the transition to interphase.

About this journal

Objective

A Journal of Biosciences: Zeitschrift für Naturforschung C (ZNC) is an international scientific journal and a community resource for the emerging field of natural and natural-like products.

The journal publishes original research on the isolation (including structure elucidation), bio-chemical synthesis and bioactivities of natural products, their biochemistry, pharmacology, biotechnology, and their biological activity and innovative developed computational methods for predicting the structure and/or function of natural products.

A Journal of Biosciences: Zeitschrift für Naturforschung C (ZNC) welcomes research papers in fields on the chemistry-biology boundary which address scientific ideas and approaches to generate and understand natural compounds on a molecular level and/or use them to stimulate and manipulate biological processes.

Topics

Bio-chemical synthesis and bioactivities of natural products
Isolation (including structure elucidation)
Biochemistry
Biotechnology
Pharmacology
Chemistry
Biology

Article formats

Original research articles, research notes, letters and review articles

Please have a look at the call for papers for two upcoming Special Issues:

Special Issue on CAZymes

Special Issue on Chitin Structures and Pathways as Targets for Biopesticides and Drugs