bluuebunny/crossref_metadata_2025 huggingface dataset:
Ascorbic acid requirement for increased peroxidase activity during potato tuber slice aging
Authors: Liso R. , De Gara L. , Tommasi F. , Arrigoni O.
Published: July 2002

The increase in peroxidase activity during aging is a well known process depending on de novo enzyme synthesis. The enhancement of peroxidase is strongly inhibited by lycorine, an ascorbic acid biosynthesis inhibitor. The inhibitory effect of lycorine can be abolished by experimentally increasing the ascorbic acid concentration in the tissues. Conversely, glucose‐6‐phosphate dehydrogenase enhancement ‐ which also occurs during the aging of potato slices ‐ depends on protein synthesis but does not require ascorbic acid. It is suggested that the role of ascorbic acid in the development of peroxidase activity may be related to controlling the synthesis of hydroxyproline‐containing proteins. A possible relationship between peroxidase increase and hydroxyproline‐containing proteins biosynthesis is discussed.
Phenoloxidase activity in Daucus carota is restricted to embryogenie cultures
Authors: Carlberg Irene , Söderhäll Kenneth , Eriksson Tage
Published: July 2002

The enzyme phenoloxidase is present in plants as a proenzyme, which is activated by Ca2+ or Mn2+ at millimolar concentrations, or by trypsin at lower Ca2+ concentrations. In Daucus carota cell cultures this proenzyme was shown to be present in the embryogenie strains, whereas the non‐embryogenic strains lacked detectable phenoloxidase activity.
Characterisation of HlyC and mechanism of activation and secretion of haemolysin from E. coli 2001
Authors: Nicaud J.-M. , Mackman N. , Gray L. , Holland I.B.
Published: July 2002

In this paper the DNA sequence of the cloned hlyC gene from E. coli 2001 is presented. The gene encodes a protein of 20 kDa which is able to activate the 107 kDa polypeptide encoded by hlyA. This gives rise to a haemolytically active protein which differs from the inactive form in stability and by its migration when analysed by polyacrylamide gel electrophoresis under non‐denaturing conditions. We also show that the inactive form is secreted in the presence of the transport functions hlyB and hlyD. This result rules out any role for the hlyC gene product in the transport of HlyA across the inner membrane
Sequence homologies and structural similarities between the polypeptides of yeast and beef heart cytochrome c oxidase
Authors: Capaldi Roderick A. , Gonzalez-Halphen Diego , Takamiya Shinzaburo
Published: July 2002

The homologous polypeptides in yeast and beef heart cytochrome c oxidase have been identified by sequence comparisons and structural similarities. The properties of individual polypeptides have been used to specify which components are extrinsic, and which intrinsic and bilayer spanning, in the cytochrome c oxidase complex.
Identification of a novel calcium‐binding protein (CP22) in multidrug‐resistant murine and hamster cells
Authors: Koch Gordon , Smith Michael , Twentyman Peter , Wright Karen
Published: July 2002

Analysis of cytoplasmic extracts of multidrug‐resistant murine and hamster cells by SDS gel and 2D gel electrophoresis showed that they expressed an abundant 22 kDa protein which was absent from the drugsensitive parent lines. SDS gel electrophoresis in the presence of EGTA and direct binding tests with 45Ca2+ showed that the resistance‐associated protein is a specific calcium‐binding protein. Thus the development of multidrug resistance in both colchicine‐selected hamster cells and adriamycin‐selected murine cells is associated with a major change in calcium metabolism. These observations provide the first molecular basis for the hypothesis that Ca2+ plays a central role in the development of the multidrug resistance phenomenon.
Protein kinase C in cytosol and cell membranes of concanavalin A‐stimulated rat thymocytes
Authors: Averdunk R. , Günther T.
Published: July 2002

In concanavalin A‐treated thymus cells and phytohemagglutinin‐treated spleen cells, the distribution of protein kinase C is changed. Shortly after addition of plant lectins, the activity of protein kinase C increased in the cytosol and decreased in the particulate fraction. 2 h later, the activity of protein kinase C decreased in the cytosol and increased in the particulate fraction. Membrane binding of protein kinase C and tion of DNA synthesis showed the same dependency on concanavalin A concentration. A long‐term membrane binding of protein kinase C seems to be essential for lymphocyte stimulation.
Rapid induction of nucleoside‐diphosphate kinase in HeLa S3 cells by human‐type interferons
Authors: Ohtsuki Kenzo , Yokoyama Minehiko , Ikeuchi Tohru , Ishida Nakao , Sugita Kenji , Satoh Kosaburo
Published: July 2002

Nucleoside‐diphosphate (NDP)‐kinase can be considered to be induced by human‐type interferons (HuIFNs) rapidly, since an enzyme increase was detected within 2 h of incubation of HeLa S3 cells with HuIFNs, while incubation with heterologous mouse IFNs had no such effect. The enzyme increase induced by HuIFNs reached a plateau at 6 h after treatment. Actinomycin D (0.5 ) significantly blocked the enzyme increase induced by HuIFNs in the cells. A possible biological role of the enzyme in the IFN‐induced biochemical events is discussed.
Phosphorylation of 3‐O‐methyl‐D‐glucose by yeast and beef hexokinase
Authors: Malaisse-Lagae Francine , Giroix Marie-Hélène , Sener Abdullah , Malaisse Willy J.
Published: July 2002

Beef heart hexokinase and yeast hexokinase both catalyzed the phosphorylation of 3‐O‐[14C]methyl‐D‐glucose. The maximal velocity was 3 orders of magnitude lower and the K
m, for the glucose analogue 40–120 times higher than those observed with D‐[U‐14C]glucose. Hence, 3‐O‐methyl‐D‐glucose should not be considered as a truly nonmetabolized analogue of D‐glucose.
Agrobacterium T‐DNA gene 1 codes for tryptophan 2‐monooxygenase activity in tobacco crown gall cells
Authors: Van Onckelen H. , Prinsen E. , Inzé D. , Rüdeisheim P. , Van Lijsebettens M. , Follin A. , Schell J. , Van Montagu M. , De Greef J.
Published: July 2002

Cloned tobacco crown gall tissue induced by the Agrobacterium
tumefaciens C58 T‐DNA mutant pGV3132, defective for the T‐DNA‐encoded amihydrolase (iaaH), accumulates about 1000‐times more indole‐3‐acet‐amide (IAM) when compared to untransformed tobacco callus and crown gall tissue induced by a T‐DNA mutant defective for gene 1. In vitro experiments demonstrated that this IAM accumulation is correlated with the active conversion of Trp into IAM. The results presented in this report provide biochemical evidence that the T‐DNA gene 1 encodes a tryptophan 2‐monooxygenase (iaaM) activity in transformed plant cells. This gene cooperates with the gene 2‐encoded amidohydrolase (iaaH) in the T‐DNA‐controlled indole‐3‐acetic acid (IAA) biosynthesis pathway in crown gall cells.
The C‐terminal, 23 kDa peptide of E. coli haemolysin 2001 contains all the information necessary for its secretion by the haemolysin (Hly) export machinery
Authors: Nicaud J.-M. , Mackman N. , Gray L. , Holland I.B.
Published: July 2002

In this paper we show the construction of a plasmid pLG609 which carries the 3'‐end of the haemolysin structural gene, hlyA under tac promoter control. Expression of pLG609 in an E. coli strain carrying the haemolysin export genes hlyB and hlyD led to the efficient secretion of the C‐terminal, 23 kDa peptide of haemolysin. The discovery of a C‐terminal topogenic sequence, which appears to be all that is required for secretion of the whole toxin, is so far quite unique in protein export.
Chromosomal loop anchorage sites appear to be evolutionarily conserved
Authors: Cockerill Peter N. , Garrard William T.
Published: July 2002

We have previously identified a class of DNA sequence elements, termed matrix association regions (MARs), which specifically bind to nuclear matrices in vitro and are believed to be at the bases of chromosomal loops in vivo [1]. Here we demonstrate that nuclear matrices prepared from the yeast Saccharomyces cerevisiae will specifically bind an MAR sequence derived from the mouse kappa light chain immunoglobulin gene. This suggests that both MAR sequences and their binding sites have been strongly evolutionarily conserved.
A novel superoxide radical generator in heart mitochondria
Authors: Nohl Hans
Published: July 2002

Experimental evidence is presented demonstrating the existence of a potent O2.−
2 source in heart mitochondria. The novel O.−
2 generator is more active than any other known mitochondrial O.−
2 generator and also exhibits a higher affinity for molecular oxygen. In contrast to mitochondrial O.−
2 sources reported previously [(1974) FEBS Lett. 42, 68–72; (1978) Eur. J. Biochem. 82, 563–567], the O.−
2 generator described in this paper is not involved in energy‐linked respiration. Superoxide radicals from this source require NADH to initiate their generation, and the radicals formed are released entirely into the extramitochondrial space. NADH‐related O.−
2 generation was also observed with the solubilized erogenous NADH oxidoreductase of heart mitochondria, an enzyme recently described [(1987) Eur. J. Biochem., submitted]. This finding together with the lack of an NADH‐dependent O.−
2 source in liver mithochondria suggests that the novel O.−
2 generator and the erogenous NADH oxidoreductase of heart mitochondria are identical.
Evidence for a signal peptide at the amino‐terminal end of human mitochondrial aldehyde dehydrogenase
Authors: Braun Thomas , Bober Eva , Singh Surjit , Agarwal Dharam P. , Goedde H.Werner
Published: July 2002

A full‐length cDNA clone coding for human mitochondrial aldehyde dehydrogenase (ALDH 1) was isolated from a human fetal muscle cDNA library. Sequence analysis revealed structural similarities between the amino‐terminal end of ALDH I and other known targeting sequences responsible for protein uptake into the mitochondria.
Short and long term influence of phenothiazines on liver peroxisomal fatty acid oxidation in rodents
Authors: Van den Branden C. , Vamecq J. , Dacremont G. , Premereur N. , Roels F.
Published: July 2002

Evidence is given that phenothiazines depress hepatic peroxisomal fatty acid oxidation in vivo. After oral administration to rats thioridazine and chlorpromazine inhibit peroxisomal β‐oxidation, evaluated by H2O2 production, during 2 weeks. In mice, this effect could not be demonstrated. However, in both species VLCFA are increased after short and long term drug administration. Electron microscopy reveals the presence of membranous structures in liver cytoplasm or lysosomes. The inhibition by thioridazine of peroxisomal β‐oxidation does not lead to hepatic peroxisome proliferation. The activities of enzymes related to fatty acid breakdown are not increased and liver peroxisomes are microscopically normal.
Demonstration that LSTRA cells have an elevated level of proteins phosphorylated on tyrosine residues
Authors: Thom Rebecca E. , Casnellie John E.
Published: July 2002

The LSTRA cell line has been shown to have an exceptionally high level of a tyrosine protein kinase (pp56lck). We now report that LSTRA cells also have a much higher level of proteins phosphorylated on tyrosine residues in comparison to several other cell lines with normal levels of pp56lck. The level of phosphotyrosine‐containing proteins in LSTRA cells was comparable to that seen in K562 cells, a cell line known to have a constitutively active tyrosine protein kinase. These results provide evidence that LSTRA cells have an elevated level of in vivo tyrosine protein kinase activity, probably due to the overexpression and activation of pp56lck.
Isolation and sequence analysis of a cDNA clone encoding a type‐1 protein phosphatase catalytic subunit: Homology with protein phosphatase 2A
Authors: Berndt Norbert , Campbell David G. , Caudwell F.Barry , Cohen Philip , da Cruz e Silva Edgar F. , da Cruz e Silva Odete B. , Cohen Patricia T.W.
Published: July 2002

A 1.5 kb clone containing the full‐length coding sequence of a type‐1 protein phosphatase catalytic subunit has been isolated from a rabbit skeletal muscle cDNA library constructed in λgt10. The protein sequence deduced from the cDNA contains 311 residues and has a molecular mass of 35.4 kDa. A single mRNA species at 1.6 kb was visualized by Northern blotting. The type‐1 protein phosphatase was strikingly homologous to protein phosphatase 2A, 49% of the amino acids between residues 11 and 280 being identical. The first 10 and last 31 residues were dissimilar. Residues 1–101 of the type‐1 protein phosphatase also showed 21% sequence identity with a region of mammalian alkaline phosphatases.
γ‐N‐Methylasparagine in phycobiliproteins from the cyanobacteria Mastigocladus laminosus and Calothrix
Authors: Rümbeli Robert , Suter Franz , Wirth Monica , Sidler Walter , Zuber Herbert
Published: July 2002

Reinvestigation of the amino acid sequences of all phycobiliproteins from Mastigocladus laminosus showed that there is a post‐translationally modified asparagine residue at position 72 of the phycobiliprotein subunits βPC, βAP and β16.2. This residue was identified as γ‐N‐methylasparagine and it was also found in βPE of Calothrix. This study also revealed some differences in the amino acid sequences βAP and βPC compared to the published data.
α‐Actinin and spectrin have common structural domains
Authors: Wasenius Veli-Matti , Närvänen Outi , Lehto Veli-Pekka , Saraste Matti
Published: July 2002

The α‐ and β‐subunits of spectrin are made of repeated homologous units of 106 residues. In the recently reported partial sequence of the chicken non‐muscle α‐actinin, a repetitive sequence homologous to the internal repeat in spectrin occurs several times. Both spectrin and α‐actinin are components of the cytoskeletal network, the integrity of which is based on multiple and complex interactions. We suggest that the shared domain structure indicates common structural principles or interactions of spectrin and α‐actinin and reflects their common evolution.
Two phytochrome‐mediated effects of light on transcription of genes encoding the small subunit of ribulose‐1,5‐bisphosphate carboxylase‐oxygenase in dark‐grown pea (Pisum sativum) plants
Authors: Barnett Linda K. , Clugston Carol K. , Jenkins Gareth I.
Published: July 2002

Pytochrome mediates two effects of light on transcription of genes encoding the small subunit of ribulose‐1,5‐bisphosphate carboxylase‐oxygenase in dark‐grown pea (Pisum sativum) plants. One response is an initial transient increase in the rate of small subunit gene transcription which results in the accumulation of a small, but relatively stable, amount of small subunit mRNA. The second is the induction of the capacity for high rates of small subunit gene transcription when plants are subsequently illuminated with white light.
Insulin increases membrane protein kinase C activity in rat diaphragm
Authors: Walaas S.I. , Horn R.S. , Adler A. , Albert K.A. , Walaas O.
Published: July 2002

Calcium/phospholipid‐dependent protein kinase activity (protein kinase C) was identified in rat diaphragm membrane and cytosol fractions by means of in vitro phosphorylation either of histones or of a specific 87 kDa protein substrate, combined with phosphopeptide‐mapping techniques. Both insulin and tumor‐promoting phorbol ester treatment of the diaphragm preparations led to increased protein kinase C activity in the membrane fractions. In contrast to the phorbol ester, however, insulin did not induce a concomitant decrease in cytosolic activity, indicating that translocation of the enzyme had not taken place. Thus, insulin appears to increase specifically membrane protein kinase C activity in rat skeletal muscle, possibly through a mechanism not identical to that induced by phorbol esters.
Interleukin‐2 binding to activated human T lymphocytes triggers generation of cyclic AMP but not of inositol phosphates
Authors: Wickremasinghe R.Gitendra , Mire-Sluis Anthony R. , Hoffbrand A.Victor
Published: July 2002

Human T lymphocytes stimulated with phytohaemagglutinin undergo a single round of cell division. Further proliferation is dependent on the lymphokine interleukin‐2 (IL2) [(1987) Immunology 60, 7–12]. We show here that binding of IL2 to its receptors on the lymphocyte surface triggers the generation of cyclic AMP. In contrast, generation of inositol phosphates from the breakdown of inositol lipids was not detected. We suggest that cyclic AMP may play a role in the transduction of the IL2 proliferative signal in T lymphocytes.
Effects of platelet‐activating factor on conversion of angiotensin I to II
Authors: Kawaguchi Hideaki , Yasuda Hisakazu
Published: July 2002

We have studied the effects of platelet‐activating factor (alkyl‐acetyl‐GPC) on conversion of angiotensin I to II. Platelet‐activating factor (PAF) had a novel effect on angiotensin I conversion. Pulmonary artery endothelial cells converted 30% of [125I]angiotensin I to angiotensin II in the absence of PAF, but their activity was greatly stimulated in its presence. When PAF was added to pulmonary artery endothelial cells, the conversion of angiotensin I to II was enhanced up to 68%. Maximal stimulation without cellular damage was achieved at 10−5 M PAF. LysoPAF did not stimulate the conversion of angiotensin I to angiotensin II at any concentration used.
Mg2+‐ATP induces filament growth from retinal rod outer segments with disrupted plasma membranes
Authors: Parker K.R. , Schaechter L.E. , Lewis J.W. , Zeman K.L. , Kliger D.S. , Dratz E.A.
Published: July 2002

Mg2+‐ATP produces a large decrease in near‐IR light scattering when added to suspensions of rod outer segments (ROS) when the plasma membranes have been disrupted by a gentle dialysis procedure. When this process is studied by light microscopy with video‐enhanced image contrast, the Mg2+‐ATP‐dependent signal is seen to be associated with the formation of filaments which extend only from those ROS lacking plasma membranes. Both the IR light scattering signal and filament growth are inhibited by vanadate and DCCD but not by colchicine, colcemid or cytochalasins.
Synthesis of spin‐labeled photoaffinity derivatives of NAD+ and their interaction with lactate dehydrogenase
Authors: Wolf A. , Fritzsche T.M. , Rudy B. , Trommer W.E.
Published: July 2002

The synthesis of NAD+ derivatives spin‐labeled at either N6 or C8 of the adenine ring is described, in which the carboxamide function of the nicotinamide moiety is replaced by a diazirine ring. Irradiation of these compounds at 350 nm generates a carbene which will react with any functional group in its vicinity including hydrocarbons. Both NAD+ derivatives form tight ternary complexes with lactate dehydrogenase and were covalently incorporated into this enzyme. They may be employed for ESR studies when non‐covalent interactions are too weak for motionally restricted species to be observed.
Novel separation method for serum immunoglobulins
Authors: Worthington J. , Chan C.-T.J. , Byfield P.G.H.
Published: July 2002

A dye‐based affinity chromatographic system using Remazol yellow GGL‐Sepharose is described for the fractionation of serum immunoglobulins. Immunoglobulins are sequentially eluted from the gel columns using gradients of pH and salt with > 88% recovery. Specific immunoglobulin activities were identified as discrete peaks and antibodies raised against the same antigen were separated. Biological properties of antibodies were retained following chromatography. The method is applicable to both human and animal immunoglobulins.
Different SH groups involved in H+ translocation and PPi hydrolysis of higher plant Mg2+‐PPiase
Authors: Verstappen Reinhold , Rausch Thomas
Published: July 2002

SH groups of the K+‐stimulated, H+‐translocating higher plant Mg2+ pyrophosphatase (Mg2+‐PPiase) are functionally characterized. A pretreatment with 50 μM N‐ethylmaleimide (NEM) in the absence of Mg2+ leads to about 50% inactivation of subsequent Mg2+‐PPi‐dependent H+‐pumping, whereas in the presence of Mg2+ no inactivation occurs. However, when PPi and Mg2+ are present during the NEM pretreatment a 50% inhibition of the subsequent H+‐pumping rate is observed. In the presence of Mg2+ and the competitive inhibitor imidodiphosphate (IDP), the NEM pretreatment does not cause inactivation, indicating that this NEM‐sensitive SH group only becomes exposed during the catalytic cycle. Conversely, PPi hydrolysis is only slightly inhibited by the 50 μM NEM pretreatment, and Mg2+‐PPi as well as Mg2+‐IDP protect PPi hydrolyzing activity against NEM inactivation. The results demonstrate the presence of different SH groups involved in PPi hydrolysis and H+ translocation.
Kinetic studies on the function of A1 in the photosystem I reaction center
Authors: Mathis P , Sétif P
Published: July 2002

Flash absorption measurements with nanosecond time resolution were conducted in the near‐ultraviolet with subchloroplast particles enriched in photosystem I, at 6°C. Around 370 nm, an absorption increase decays biphasically, with a fast phase, t

= 15 ± 5 ns. Control experiments show that this rapid phase is due to the reoxidation of A1 (presumably phylloquinone), which thus appears to function as an electron carrier in PS I at physiological temperature. The nanosecond kinetic phase is not altered if the iron‐sulfur centers FA and FB are kept reduced.
Processing of the D1 polypeptide of the photosystem II reaction centre and photoactivation of a low fluorescence mutant (LF‐1) of Scenedesmus obliquus
Authors: Taylor M.A. , Packer J.C.L. , Bowyer J.R.
Published: July 2002

In the LF‐1 mutant of Scenedesmus obliquus, a failure to remove a C‐terminal extension from the D1 protein of photosystem II (PS II) is associated with the absence of a water‐splitting manganese complex. Treatment of LF‐1 thylakoids and PS II‐enriched membranes with a Triton X‐100 extract of wild‐type thylakoids results in a specific reduction in molecular mass of the LF‐1 D1 to the same value as that in wild‐type membranes. Water‐splitting activity can be photogenerated in these extract‐treated LF‐1 PS II‐enriched membranes, and in PS II membranes from dark‐grown wild‐type cells, but not in untreated LF‐1 membranes. The results indicate that LF‐1 cells lack the D1 processing protease, and that the presence of the D1 extension in LF‐1 is directly responsible for preventing assembly of the manganese complex.
Hydroxyprolyl3‐bradykinin in high molecular mass kininogen presence in human and monkey kininogens, but not in kininogens from bovine, rat, rabbit, guinea pig and mouse plasmas
Authors: Enjyoji Kei-ichi , Kato Hisao
Published: July 2002

The contents of hydroxyprolyl3‐bradykinin in high molecular mass (HMM) kininogens from human and animal plasmas were examined by reversed‐phase HPLC following their proteolytic scission by bovine plasma kallikrein. The relative contents of hydroxyprolyl3‐bradykinin in kinins from HMM kininogens from pooled plasmas of human and monkey origin were 33 and 73%, respectively. On the other hand, hydroxyprolyl3‐bradykinin could not be detected in HMM kininogen preparations from bovine, rat, guinea pig, rabbit and mouse plasmas. Hydroxyproline in hydroxyprolyl3‐bradykinin was assigned as trans‐4‐hydroxyproline by comparison of the retention times on reversed‐phase HPLC with isomers of hydroxyproline after derivatization with 7‐chloro‐4‐nitrobenzo‐2‐oxa‐1,3‐diazole chloride.
31P NMR study of daunorubicin‐d(CGTACG) complex in solution Evidence of the intercalation sites
Authors: Ragg E. , Mondelli R. , Battistini C. , Garbesi A. , Colonna F.P.
Published: July 2002

The interaction of daunorubicin with the self‐complementary DNA fragment d(CGTACG) was studied by 31P NMR spectroscopy. The individual phosphates have been assigned for the nucleotide and the complex and signals from bound and free species in slow exchange at 19°C were detected. In solution, the hexanucleotide binds two molecules of daunorubicin, which intercalate in the d(CG) sequence at both ends of the helix. Evidence for local deformations of the backbone at the sites of C5pG6, C1pG2 and G2pT3 phosphates is given. The binding constants for the stepwise equilibrium and the rate of dissociation of the intercalated duplex were also determined.
3′:5′‐Cyclic GMP in the yeast Saccharomyces cerevisiae at different metabolic conditions
Authors: Eckstein Hans
Published: July 2002

cGMP is characterized as undetectable in yeast [(1986) Yeast Cell Biology, UCLA Symp. Mol. Cell Biol. (Hicks, J. ed.) p.495], though in many organisms it contributes specifically to the regulation of metabolism. Here, we detected cGMP, using radioactive labeling and RIA techniques, after extraction of the cells with mol/1 HClO4 at 37°C. The cGMP 0.015‐fold cAMP, about 3 times higher with exponentially growing cells than with pressed baker's yeast, and depends on glucose and O2 supply. The PDE inhibitors DMX and IBMX induce in growing cells an additional increase of the cGMP level, without similar effects on cAMP.
Plasma membrane transglutaminase and cytosolic transglutaminase form distinct envelope‐like structures in transformed human keratinocytes
Authors: Schmidt Rainer , Michel Serge , Shroot Braham , Reichert Uwe
Published: July 2002

Cross‐linked envelope formation in the transformed human keratinocyte line SV‐K14 requires treatment of the cells with a Ca2+ ionophore. Depending on the culture conditions, different extracellular Ca2+ concentrations are necessary to trigger the process which is catalyzed by the enzyme transglutaminase. Confluent cells grown in the presence of serum express only the cytosoluble form of the enzyme and need 5 mM Ca2+ for optimum protein cross‐linking, whereas serum‐starved cells which additionally contain the plasma membrane associated form of the enzyme require only 1 mM Ca2+. The envelope‐like structures thus synthesized are morphologically and biochemically distinct.
The antimycin sensitivity of flash‐induced ATP synthesis in photosystem I‐enriched subchloroplast vesicles
Authors: de Wolf F.A. , Galmiche J.M. , Kraayenhof R.
Published: July 2002

Photosystem I‐enriched vesicles, derived from spinach thylakoids by mild digitonin treatment, reconstituted with native ferredoxin and redox‐poised with NADPH and oxygen, display antimycin‐sensitive cyclic photophosphorylation. The effects of 1–30 μM antimycin point to electron transfer inhibition: (i) they are cancelled after addition of 10 μM pyocyanin and (ii) they resemble the effects of 1–5 μM DBMIB, but differ from those of FCCP, nigericin or valinomycin. Some vesicle preparations fails to show antimycin sensitivity in the absence of pyocyanin [(1985) FEBS Lett. 192, 271–274] and have apparently lost the antimycin‐sensitive component.
Localization of melted regions in supercoiled DNA
Authors: Voloshin O.N. , Shlyakhtenko L.S. , Lyubchenko Yu.L.
Published: July 2002

Diethyl pyrocarbonate (DEPC) was used as a probe of local denatured regions in ccDNA pAO3 plasmid. It was found that in native ccDNA molecules only adenosine residues in the loop of the cruciform structure react with DEPC. Denaturation of ccDNA is accompanied by the appearance of two short regions (20 bp long) at both borders of the cruciform structure. Further increase in the denaturation process is associated with considerable expansion of the region located to the left of the cruciform, while the cruciform structure itself and the denatured region located to the right of it disappear.
Particular processing of pro‐opiomelanocortin in Xenopus laevis intermediate pituitary Sequencing of α‐ and β‐melanocyte‐stimulating hormones
Authors: Rouillé Y. , Michel G. , Chauvet M.T. , Chauvet J. , Acher R.
Published: July 2002

α‐ and β‐melanocyte‐stimulating hormones (α‐MSH and β‐MSH) have been isolated from Xenopus laevis neurointermediate pituitary and microsequenced. Intracellular α‐MSH is not N‐acetylated after proteolytic processing of pro‐opiomelanocortin in contrast to mammalian α‐MSHs. There is a high preservation of the melanotropic amino acid sequence common to all MSHs although in Xenopus β‐MSH a histidine residue replaces the glutamic acid residue found in position 8 of mammalian β‐MSHs.
The effect of nonreceptor adsorption on the lethal action of colicin E1
Authors: Malkhosyan S.R. , Rekesh A.N.
Published: July 2002

The survivability of Escherichia coli K12s cells has been studied after treatment with 125I‐labeled colicin E1. It has been shown that for low amounts of adsorbed colicin the survivability follows single‐hit kinetics. When the number of colicin molecules adsorbed exceeds approx. 50 per cell, deviation from single‐hit kinetics occurs towards higher survivability. Colicin E1 adsorbed nonreceptorwise by the cell's surface has been shown to inhibit the lethal action of colicin E1 molecules adsorbed at specific receptors. This fact has been used in accounting for the elevated survivability of cells at high colicin doses. The functional significance of the phenomenon is discussed.
Transport of influenza virus envelope proteins from the Golgi complex to the apical plasma membrane in MDCK cells: pH‐Controlled interaction with a cycling receptor is not involved
Authors: Daniels-Holgate Phillipa U. , Edwardson J.Michael
Published: July 2002

In influenza virus‐infected monolayers of the epithelial cell line MDCK the viral envelope proteins, haemagglutinin and neuraminidase, are targetted specifically to the apical surface. In this study we have tested the hypothesis that the polarized delivery of these proteins to the plasma membrane involves the operation of a receptor that cycles between the trans Golgi network and the plasma membrane, binding the proteins at low pH in the former compartment and releasing them at normal extracellular pH in the latter. The hypothesis predicts that apical, but not basolateral, low pH would eventually delay or block delivery of the proteins to the plasma membrane. We found that basolateral low pH in fact had the more profound effect, in line with its greater effect on intracellular pH. We conclude that the hypothesis is not valid, and that low extracellular pH causes its effect on protein transport by changing intracellular pH.
Selection of the 3′‐splice site in group I introns
Authors: Burke John M.
Published: July 2002

A model for selection of 3′‐splice sites in splicing of RNA precursors containing group I introns is presented. The key feature of this model is a newly identified tertiary interaction between the catalytic core of the intron and the 3′‐splice site. This tertiary pairing would bring the 3′‐splice site into the core of the intron, which is known to contain RNA sequences and structures essential for catalyzing the splicing reactions. The proposed tertiary interaction can coexist with P10, a pairing between 3′‐exon sequences and the ‘internal guide sequence’ near the 5′‐end of the intron. The model predicts that three RNA‐RNA interactions are important in selection of 3′‐splice sites: (i) binding of intron sequences with the core; (ii) pairing of exon sequences with the internal guide sequence; and (iii) binding of the terminal guanosine to an unknown site within the core.
Enhancement of colony forming ability in the lung by transfer of the v‐fos oncogene into a ras‐transformed rat 3Y1 cell line
Authors: Nakamatsu Kohji , Taniguchi Shun'ichiro , Kimura Genki , Baba Tsuneo
Published: July 2002

Transfer of the v‐fos oncogene into a rat 3Y1 cell line transformed by v‐H‐ras, which is tumorigenic but non‐metastatic, enhanced lung metastasis, depending on the amount of fos‐related transcripts. Enhancement of the metastatic potential was associated with increases in tumor growth rate i.m. of inoculated cells but not the rate of in vitro cell growth, irrespective of the addition of tissue (e.g. lung) extract to the regular medium. These results suggest that the v‐fos oncogene increased the malignancy by altering biological factors of the recipient cells responsible for cell growth and/or survival rate in vivo.
New crystal forms of the small subunit of ribonucleotide reductase from Escherichia coli
Authors: Nordlund Par , Uhlin Ulla , Westergren Christina , Joelsen Thorleif , Sjöberg Britt-Marie , Eklund Hans
Published: July 2002

The small subunit of ribonucleotide reductase from Escherichia coli has been crystallized in two new crystal forms. The form most suitable for X‐ray analysis belongs to the orthorhombic space group P212121. It,has the cell dimensions 74.3 Å, 85.5 Å, 115.7 Å and diffracts to about 2.1 Å resolution. The asymmetric unit most probably contains one dimer. Absorption spectra of single crystals confirm that the crystals contain a binuclear iron center. Crystals of the iron‐depleted apoenzyme have also been obtained.
Constitutive in vitro binding of nuclear proteins to the 5'‐fanking region of 6–16, a human gene inducible by α, β‐interferons
Authors: Chernajovsky Yuti
Published: July 2002

Proteins in nuclear extracts of HeLa cells that constitutively bound in vitro to three regions upstream of the interferon‐inducible gene 6–16 were separated partially by chromatography on DEAE‐Sepharose. Region one, a CCAAT box in the non‐coding strand at position −63 to −67, was protected from DNase digestion by the bound protein(s) and was required for transcription in vitro. Region two, a tandem duplication sequence at position −89 to −168 contains two copies of a sequence essential for strong induction of the 6–16 gene by interferon in vivo. Region three, a palindromic sequence at position −449 to −465, not necessary for induction of 6‐16 by interferon, was also protected from DNase digestion by nuclear protein(s). Templates with or without regions of two and three were transcribed equally well in extracts from interferon‐treated or untreated cells.
Carbamylcholine inhibits β‐adrenergic receptor‐coupled Gs protein function proximal to adenylate cyclase
Authors: Avissar Sofia , Schreiber Gabriel
Published: July 2002

The specific mechanism by which the inhibitory guanine nucleotide binding protein (Gi) mediates the inhibition of adenylate cyclase activity is still unclear. The subunit dissociation model, based on studies in purified or reconstituted systems, suggests that the βγ subunit, which is dissociated with activation of Gi, inhibits the function of the stimulatory guanine nucleotide binding protein (Gs) by reducing the concentration of the free αs subunit. In the present study, Gs, protein function is determined by measuring cholera toxin‐blockable, isoproterenol‐induced increases in guanosine triphosphate (GTP) binding capacity to rat cardiac ventricle membrane preparations. Carbamylcholine totally inhibited this β‐adrenergic receptor‐coupled Gs protein function. Pretreatment of the cardiac ventricle membrane preparation with pertussis toxin prevented this muscarinic agonist effect. These results confirm the possibility of an inhibitory agonist‐receptor coupled effect through Gi on Gs protein function proximal to the catalytic unit of adenylate cyclase in an intact membrane preparation.
Fluoride activates diradylglycerol and Superoxide generation in human neutrophils via PLD/PA phosphohydrolase‐dependent and ‐independent pathways
Authors: Olson Susan C. , Tyagi Shiv Raj , Lambeth J.David
Published: July 2002

In contrast to the rapid, ethanol‐inhibited Superoxide generation by the receptor‐linked agonist formyl‐methionyl‐leucyl‐phenylalanine (fMLP), fluoride‐activated Superoxide generation occurs after a prolonged lag, and as shown herein is relatively ethanol‐insensitive. We have investigated fluoride‐activation of diradylglycerol generation and phospholipase D activity. Fluoride induces a very large increase in diradylglycerol mass (both 1,2‐diacylglycerol (DAG) and 1‐O‐alkyl,2‐acylglycerol (EAG)), with kinetics similar to Superoxide generation. Unlike fMLP‐activated diglyceride generation which is completely inhibited by ethanol, that produced by fluoride is only partially (30%) blocked. When the phosphatidylcholine pool is 3H‐prelabeled, fluoride activates both [3H]phosphatidic acid (PA) and [3H]diglyceride generation with similar kinetics. Partial inhibition of the production of these species by ethanol was seen, coincident with the appearance of [3H]phosphatidylethanol, indicating phospholipase D‐dependent transphosphatidylation had occurred. The data are consistent with the fluoride activation of PA and diglyceride generation by both phospholipase D‐dependent and ‐independent (presumably phospholipase C) mechanisms.
A novel enzymatic decarboxylation of oxalic acid by the lignin peroxidase system of white‐rot fungus Phanerochaete chrysosporium
Authors: Akamatsu Y. , Ma D.B. , Higuchi T. , Shimada M.
Published: July 2002

Oxidation of veratryl alcohol by lignin peroxidase (LiP) was potently inhibited by oxalic acid. The inhibition analysis with Lineweaver‐Burk plots clearly showed that the type of inhibition is non‐competitive. The enzymatic oxidation of veratryl alcohol in the presence of 14C‐oxalic acid yielded radioactive carbon dioxide. The results indicate that the apparent inhibition of LiP is caused by reduction of the veratryl alcohol cation radical intermediate back to the substrate level by oxalate, which is concomitantly oxidized to carbon dioxide.
DNA methylation inhibits transcription by RNA polymerase III of a tRNA gene, but not of a 5S rRNA gene
Authors: Besser Daniel , Götz Frank , Schulze-Forster Kai , Wagner Herbert , Kröger Hans , Simon Dietrich
Published: July 2002

Methylation of cytosine in the DNA inhibits the transcription by RNA polymerase II in higher eukaryotes, but has no influence on RNA polymerase I transcription. The effect on RNA polymerase III was unknown, so far. Two polymerase III genes: a type 1 5S rRNA gene and a type 2 tRNA gene were methylated in vitro with a purified eukaryotic DNA methyltransferase (EC2.1.1.37) and their transcription was analyzed in Xenopus oocytes. The 5S rRNA gene, an oocyte 5S rRNA gene from X. laevis which is subject to developmental inactivation, was not affected by methylation. Conversely, transcription of the tRNA gene was 80% inhibited by methylation with the eukaryotic methyltransferase. HhaI and HpaII methylation left its transcription unaffected.
Enzyme‐enzyme interactions and their metabolic role
Authors: Srere Paul A. , Ovadi Judit
Published: July 2002

There are continuing reports on the existence of complexes of sequential metabolic enzymes. New techniques for their detection have been described and include affinity electrophoresis and the use of anti‐idiotypic antibodies. Channeling of substrates has been reported for several systems as well as direct substrate transfer through dynamic enzyme associations. Kinetic parameters of metabolic control of organized systems have been formulated and tested in several systems. These recent results are expanding our understanding of metabolic processes and their control.
Direct analysis of peptides and amino acids from capillary electrophoresis
Authors: Bergman Tomas , Agerberth Birgitta , Jörnvall Hans
Published: July 2002

Capillary zone electrophoresis of peptides on a preparative scale and direct analysis of both amino acid sequences and compositions are demonstrated. Using native and synthetic peptides prepared by repetitive runs and appropriate collections, sufficient material for direct sequence analysis is obtained after just a few runs, while single runs suffice for total compositions. Electrophoretic direct amino acid analysis without derivatization is also possible and gives especially high sensitivity for aromatic residues (<200 fmols) plus convenient distinction of amidated versus free C‐terminal residues after carboxypeptidase digestions.
Ubiquitin—protein conjugates and αB crystallin are selectively present in cells undergoing major cytomorphological reorganisation in early chicken embryos
Authors: Scotting Paul , McDermott Helen , Mayer R.John
Published: July 2002

Ubiquitin—protein conjugates and αB crystallin are detected immunohistochemically in cells undergoing extensive morphological reorganisation in early chicken embryos. Cytoplasmic ubiquitinated proteins and αB crystallin are coordinately found in cells of the lens, notochord and myotome. The antigens appear in the myotome cells precisely, at the point at which the cells begin to migrate from the dorsomedial lip of the dermamyotome. The findings indicate that ubiquitin and αB crystallin may have a coordinate role in the extensive architectural remodeling which occurs in these developing tissues in the early chick embryo, Some form of functional association between protein ubiquitination and αB crystallin in cells may explain why αB crystallin is found with ubiquitin—protein deposits in some neurodegenerative diseases.
A metallothionein‐like gene from maize (Zea mays) Cloning and characterization
Authors: de Framond Annick J.
Published: July 2002

A differentially expressed maize gene has been cloned and sequenced. Transcriptional and translational start sites have been mapped and 2.5 kb of 5′ flanking DNA were sequenced. The 8 kDa protein encoded by this gene shows striking similarity to the metallothionein‐like proteins recently described in Pisum sativum [1] and Mimulus guttatus [2]. The maize MT‐L gene message is very abundant in roots without exposure to high levels of metals, present at lower concentration in leaves and pith, and at very low concentration in seed.
Molecular cloning of a human gene (S31) encoding a novel serotonin receptor mediating inhibition of adenylyl cyclase
Authors: Levy Finn Olav , Gudermann Thomas , Birnbaumer Mariel , Kaumann Alberto J. , Birnbaumer Lutz
Published: July 2002

We report the molecular cloning of human gene (S31) containing an open reading frame of 1095 nucleotides, which encodes a protein of 365 amino acids. The encoded protein contains seven hydrophobic putative transmembrane domains considered the hallmark of G protein‐coupled receptors. The amino acid sequence shows highest homology to receptors for serotonin (5‐hydroxytryptamine). Expression of this receptor in murine Ltk
− cells conferred upon these cells the ability to respond to serotonin by inhibition of adenylyl cyclase. No response was observed to isoproterenol, epinephrine, histamine, dopamine or melatonin in the transfected cells. We propose that the human gene S31 encodes a novel serotonin receptor.
The active site structure of methane monooxygenase is closely related to the binuclear iron center of ribonucleotide reductase
Authors: Nordlund Pär , Dalton Howard , Eklund Hans
Published: July 2002

Methane monooxygenase (MMO) catalyses the biological transformation of methane to methanol at a binuclear iron site. Guided by the three‐dimensional structure of the R2 protein of E. coli ribonucleotide reductase (RNR), we have aligned the sequences of two different MMOs with the sequences of the iron coordinating four helix bundle in R2. The model suggests that the central four helix bundle of R2 is present also in MMO. The iron coordination is similar in MMO and R2 with two histidine ligands and four carboxyl ligands in both cases. The residues lining the proposed oxygen binding site in MMO are significantly smaller in MMO than in R2 allowing binding of both molecular oxygen and methane at this site. This binding site is lined by residues Cys151, Thr213, Ile217 and Ile(Val)239.
Detection of the optical bands of molybdenum(V) in DMSO reductase (Rhodobacter capsulatus) by low‐temperature MCD spectroscopy
Authors: Benson Neil , Farrar Jaqui A. , McEwan Alastair G. , Thomson Andrew J.
Published: July 2002

Dimethylsulphoxide (DMSO) reductase from R. capsulatus contains a molybdenum‐pterin cofactor at its active site. As prepared the molybdenum is in the 6+ oxidation state, devoid of EPR signals. Stepwise reduction generates an EPR signal characteristic of Mo(V) having hyperfine coupling to a single proton and integrating to less than 25% of the total molybdenum. The low temperature MCD spectrum shows oppositely signed bands between ∼550–700 nm. These bands are assigned as dithiolene‐to‐Mo(V) charge transitions. A simple theoretical model can satisfactorily account for the bands in the MCD spectrum. No evidence is found for cysteine coordination to Mo(V).
Microcin E492 forms ion channels in phospholipid bilayer membranes
Authors: Lagos Rosalba , Wilkens Marcela , Vergara Cecilia , Cecchi Ximena , Monasterio Octavio
Published: July 2002

Microcin E492, a polypeptide antibiotic, has been shown to have an M
r, of 6,000 by urea‐SDS‐polyacrylamide gel electrophoresis of the fluorescently labelled compound. It is known that the bactericidal action of microcin involves a loss of the transmembrane potential. In this study we show that microcin forms cation‐selective channels in planar phospholipid bilayers. The channels have two main conductance states the current‐voltage curves of which rectify. The reversal potentials measured under biionic conditions indicate a permeability sequence of NH4
+ > K+ = Rb+ = Cs+ > Na+ = Li+ > Tris+. The results suggest that membrane potential dissipation induced by microcin is a consequence of the formation of pores in the bacterial membrane.
Determination of a functional lysine residue of a plant cysteine synthase by site‐directed mutagenesis, and the molecular evolutionary implications
Authors: Saito Kazuki , Kurosawa Makoto , Murakoshi Isamu
Published: July 2002

Comparison of seven deduced amino acid sequences of cysteine synthase (O‐acetyl‐l‐serine (thiol)‐lyase, EC 4.2.99.8) from plants and bacteria disclosed the presence of 12 conserved Lys residues, which can be candidates for a functional binding site for pyridoxal phosphate cofactor. These 12 conserved Eys residues in a cDNA clone encoding spinach cysteine synthase A were replaced with Gly by oligonucleotide‐directed in vitro mutagenesis. These Lys → Gly mutated cDNAs were transferred into Escherichia coli NK3, a cysteine auxotroph lacking both cysteine synthase loci, cysKand cysM. One mutant replaced at Lys‐49 could not complement the cysteine requirement of NK3, whereas other mutants and wild‐type clone could. No enzymatic activity of cysteine synthase A was detected either in the cell‐free extracts of E coli NK3 transformed with the Lys‐49 mutant. These results indicated that Lys‐49 is a functional residue for the catalytic activity of cysteine synthase. This Lys residue is conserved in other evolutionarily related amino acid‐metabolizing enzymes catalyzing reactions involving the β‐carbon of amino acids.
Cyanide‐reactive sites in cytochrome bd complex from E. coli
Authors: Krasnoselskaya Irina , Arutjunjan Alexander M. , Smirnova Irina , Gennis Robert , Konstantinov Alexander A.
Published: July 2002

Cyanide reacts with cytochrome bd from E. coli in an ‘aerobically oxidized’ state (mainly, an oxygenated complex b
558
3+
b
595
3+
d
2+‐O2), bringing about (i) decomposition of the heme d
2+ oxycomplex (decay of the 648 nm absorption band) and (ii) extensive red shift in the Soret region accompanied by minor changes in the visible range assigned to ferric heme b
595. MCD spectra show that the Soret red shift is associated with heme b
558
3+ high‐to low‐spin transition. This is the first unambiguous demonstration that heme b
595 can bind exogenous ligands. No reaction of cyanide with b
558 is observed. In about 70% of the enzyme which forms the cyano complex, the spin‐state transition of b
595 decay of heme d oxycomplex match each other kinetically (k
eff ca. 0.002 s−1 at 50 mM KCN, pH 8.1, 25°C). This points to an interaction between the two hemes. The concerted binding of cyanide to d
3+ and b
595
3+, perhaps as a bridging ligand, is probably rate‐limited by d
2+ oxycomplex autoxidation. In the remaining 30% of the isolated bd, there is a rapid phase of cyanide‐induced b
595 spin‐state transition which can be tentatively assigned to that proportion of the enzyme in which heme d is initially in the ferric rather than ferrous‐oxy form.