bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of a second Escherichia coli groE gene whose product is necessary for bacteriophage morphogenesis.
Authors: Tilly K , Murialdo H , Georgopoulos C
Published: May 2006

Previous work has uncovered the existence of an Escherichia coli locus, groE, that is essential for bacterial growth, lambda phage and T4 phage head morphogenesis, and T5 phage tail assembly. Our genetic and biochemical analyses of lambda groE+ transducing phages and their deletion and point mutant derivatives show that the groE locus consists of two closely linked genes. One groE gene, groEL, has been shown to encode the synthesis of a 65,000 Mr polypeptide, whereas the second, groES, codes for the synthesis of a 15,000 Mr polypeptide. About half of the groE- bacterial isolates fall into the groES complementation group. GroE mutations in either gene cause similar phenotypes, with respect to lambda phage head morphogenesis and bacterial growth at nonpermissive temperatures.
Resonance Raman spectroscopy of specifically [epsilon-15N]lysine-labeled bacteriorhodopsin.
Authors: Argade P V , Rothschild K J , Kawamoto A H , Herzfeld J , Herlihy W C
Published: May 2006

The possible interaction of a second lysine with the retinylidene Schiff base of bacteriorhodopsin (Lewis, A., Marcus, M. A., Ehrenberg, B. & Crespi, H. (1978) Proc. Natl. Acad. Sci. USA 75, 4642-4646) has been investigated by specific incorporation of 15N into the epsilon-amino groups of the lysine residues. Comparison of resonance Raman spectra of bacteriorhodopsin grown on 100%, 0%, and 50% labeled lysine demonstrates that 15N isotope effects on the Schiff base vibration can be accounted for by 15N labeling only at the Schiff base nitrogen. Our data also provide in situ confirmation of the linkage of the retinal chromophore with the epsilon-amino nitrogen of lysine.
Related 5S RNA transcription factors in Xenopus oocytes and somatic cells.
Authors: Pelham H R , Wormington W M , Brown D D
Published: May 2006

Xenopus oocytes contain an abundant protein that binds specifically to the center of 5S RNA genes and directs their transcription by RNA polymerase III. This protein also binds to 5S RNA. We show here that transcription of cloned 5S RNA genes in extracts derived from Xenopus tissue culture cells is dependent on the intragenic control region and is inhibited by 5S RNA and by antibodies raised against the previously characterized oocyte transcription factor. Somatic cells contain a protein that is similar to the oocyte factor in charge, affinity for heparin-agarose, and antigenicity but has an apparent molecular mass about 2000 daltons greater than that of the oocyte protein. Our experiments strongly suggest that this larger protein is the transcription factor for 5S RNA genes in somatic cells. The 5S RNA may regulate its own synthesis in somatic cells by binding to this protein, which is present at a low concentration. The presence of two different proteins responsible for 5S RNA synthesis in oocytes and in somatic cells cannot by itself explain the developmental control of oocyte and somatic 5S RNA genes, because somatic cell extracts transcribe both types of gene.
Epstein-Barr virus RNA VII: size and direction of transcription of virus-specified cytoplasmic RNAs in a transformed cell line.
Authors: van Santen V , Cheung A , Kieff E
Published: May 2006

At least three separate regions of the Epstein-Barr virus (EBV) genome encode RNA in a cell line that is growth transformed and nonpermissively infected with EBV. Six polyadenylylated cytoplasmic RNAs have been identified from these three regions. An abundant RNA 3.0-3.1 kilobases (kb) long is encoded by DNA of the internal reiteration, IR, and DNA that maps at 25.7-30 megadaltons. A second, abundant, 2.9-kb RNA is primarily encoded by DNA at 110-03 megadaltons but probably has a 3' end to the left of 110 megadaltons. A third, abundant, 3.7-kb RNA is largely encoded by DNA at 63-66 megadaltons and has a 5' end to the left of 63 megadaltons. A less-abundant 1.5-kb RNA is also encoded by IR. The least-abundant polyadenylylated RNAs identified are 2.3 and 2.0 kb. These RNAs have 3' ends mapping of 5-7 megadaltons and 5' ends mapping to the right of 7 megadaltons. The data suggest that there may be two additional polyadenylylated cytoplasmic RNAs, a 3-kb RNA mapping at 26.2-30 megadaltons and a minor RNA mapping at 102-110 megadaltons. An abundant 0.16-kb nonpolyadenylylated RNA is also present in the cytoplasm of IB-4 cells. This RNA precipitates from the cytoplasm in the presence of high concentrations of magnesium, indicating that it is complexed with protein or polyribosomes.
Autoradiographic localization of benzodiazepine receptors in immunocytochemically identified gamma-aminobutyrergic synapses.
Authors: Möhler H , Richards J G , Wu J Y
Published: May 2006

Benzodiazepine receptors can be visualized in regions of synaptic contact by electron microscopic autoradiography using [3H]flunitrazepam as a photoaffinity label in fresh brain tissue. Perfusion fixation of the tissue prior to photoaffinity labeling left the ligand binding characteristics and the light and electron microscopic distribution of benzodiazepine receptors unaltered. Therefore, the immunocytochemical localization of a neuronal marker in fixed tissue could be combined with photoaffinity labeling in order to identify the types of synapses containing benzodiazepine receptors. By using antiserum to glutamate decarboxylase, a marker of gamma-aminobutyrergic neurons, one-third of the photolabeled benzodiazepine receptors were found to be associated with immunocytochemically stained nerve endings. Thus, these synapses are the site of at lest some benzodiazepine receptors. The enhancement of gamma-aminobutyrergic synaptic transmission by benzodiazepines, shown electrophysiologically, appears to be a primary mechanism of action of this group of drugs.
Sexually dimorphic brain and behavioral asymmetries in the neonatal rat.
Authors: Ross D A , Glick S D , Meibach R C
Published: May 2006

The 2-deoxy-D-glucose method was used to study asymmetries in cerebral metabolic activity in neonatal rats. Left-right asymmetries in 2-deoxy-D-glucose uptake were observed in hippocampus, diencephalon, cortex, and medulla-pons: 2-deoxy-D-glucose incorporation was greater in right hippocampus, right diencephalon, left cortex, and left medulla-pons. These asymmetries occurred only in females. We also observed neonatal asymmetries in tail position that, in both sexes, were predictive of adult turning preferences; females had right-sided biases in both neonatal and adult characteristics. Collectively these data indicate that cerebral lateralization is sexually dimorphic and is present at birth.
Oxidation of phenylhydroxylamine in aqueous solution: a model for study of the carcinogenic effect of primary aromatic amines.
Authors: Becker A R , Sternson L A
Published: May 2006

Phenylhydroxylamine is degraded in aqueous phosphate buffers at physiological pH values (6.8-7.4) to give nitrosobenzene, nitrobenzene, and azoxybenzene. The reaction is O2 dependent and subject to general acid and general base catalysis. At pH less than or equal to 5.8 in cacodylate buffer, it is converted to p-nitrosophenol in addition to nitrosobenzene, nitrobenzene, and azoxybenzene. Nitrobenzene and p-nitrosophenol appear to form directly from phenylhydroxylamine. A common intermediate generated from phenylhydroxylamine and O2 is suggested to account for the formation of nitrobenzene, nitrosobenzene, and p-nitrosophenol and is consistent with kinetic studies and 18O-labeling experiments. The results suggest that neither hydrogen peroxide nor superoxide (O-2) are involved in the oxidation sequence.
On the density matrix approach of intramolecular relaxation processes
Authors: Lin S. H. , Eyring H.
Published: May 2006

In this paper we derive the generalized master equations for the
S
1
system coupled with the
S
2
system, with the
S
1
and
S
2
systems embedded in a heat bath. This formalism can be applied to a number of problems like vibrational redistribution, dynamic effect of vibrational relaxation on electronic relaxation in condensed media, etc. In this paper the importance of the memory function associated with a relaxation process is emphasized.
Nucleotide sequence of the 26S mRNA of Sindbis virus and deduced sequence of the encoded virus structural proteins.
Authors: Rice C M , Strauss J H
Published: May 2006

The nucleotide sequence of intracellular 26S mRNA of Sindbis virus has been determined by direct sequence analysis of the cDNA made to this RNA with reverse transcriptase. From this, the amino acid sequences of the encoded virus structural proteins, which include a basic capsid protein and two integral membrane glycoproteins, have been deduced. The features of these proteins as related to their functions are discussed. We suggest that three proteases are required to produce these proteins from their polyprotein precursor: a viral protease, which functions in the cytosol to release the capsid protein, signalase, which makes two cleavages to separate the glycoproteins; and a protease of the Golgi complex that cleaves after double basic residues, to process the precursor form of one of the glycoproteins.
Abelson murine leukemia virus: molecular cloning of infectious integrated proviral DNA.
Authors: Srinivasan A , Reddy E P , Aaronson S A
Published: May 2006

The integrated proviral genome of Abelson murine leukemia virus (A-MuLV) was cloned in lambda gtWES . lambda B bacteriophage after EcoRI endonuclease digestion and enrichment of proviral sequences by sequential RPC-5 column chromatography and agarose gel electrophoresis. Recombinant DNA clones containing a 7.8-kilobase-pair EcoRI insert were shown to have the entire integrated A-MuLV genome with both 5' and 3' ends flanked by mink cellular DNA sequences. This DNA fragment was shown to induce focus transformation upon transfection of NIH/3T3 mouse cells. Moreover, focus-forming virus could be rescued from transformed nonproducer cells upon superinfection with a type C helper virus. A polyprotein of molecular weight 120,000 (p120) containing murine leukemia virus gag gene determinants was invariably deteced by immunoprecipitation analysis of individual transformants induced by the 7.8-kilobase-pair DNA. Molecularly cloned integrated A-MuLV in its infectious form should be of use in elucidating the mechanisms involved in transformation by this virus.
Nitrogen regulatory locus "glnR" of enteric bacteria is composed of cistrons ntrB and ntrC: identification of their protein products.
Authors: McFarland N , McCarter L , Artz S , Kustu S
Published: May 2006

The nitrogen regulatory locus "glnR" of Escherichia coli and Salmonella typhimurium is composed of two cistrons, which we propose to call ntrB and ntrC (nitrogen regulation B and C). Frameshift mutations in ntrB and ntrC were isolated on a lambda phage that carries the E. coli ntrB and ntrC genes and the closely linked glnA gene, the structural gene encoding glutamine synthetase [L-glutamate:ammonia ligase (ADP-forming), EC 6.3.1.2]; mutations were selected as suppressors of glnF (which we propose to rename ntrA), a selection used previously to isolate glnR mutations. Phage DNA from one mutant (ntrB) failed to direct synthesis of a 36-kilodalton (kDal) protein whose synthesis was directed by DNA from the parent phage (ntrB+) in a coupled in vitro transcription/translation system. DNA from three other mutants (ntrC) failed to direct synthesis of a 54-kDal protein; DNA from two of these mutants instead directed synthesis of smaller proteins, 53 and 50 kDal, respectively. In all four cases, DNA from frameshift revertants directed synthesis of both the 36-kDal and 54-kDal proteins. These results suggested that ntrB and ntrC were separate genes which encoded 36-kDal and 54-kDal protein products, respectively. Frameshift mutations in ntrB and ntrC complemented each other with regard to regulation of glnA expression in vivo and growth on arginine as nitrogen source, another nitrogen-controlled phenotype; this confirmed that ntrB and ntrC are separate cistrons that encode diffusible products. The ntrB and ntrC genes were also defined in S. typhimurium. Studies of mutant strains provided information on the roles of the ntrB and ntrC products in activation and repression of glnA expression and raised the possibility that these products function as a protein complex in regulating expression of nitrogen-controlled genes.
Secondary structure of eukaryotic cytoplasmic 5S ribosomal RNA.
Authors: Luehrsen K R , Fox G E
Published: May 2006

A five-helix secondary structural model is proposed for eukaryotic cytoplasmic 5S rRNA. All available sequence data are consistent with this model including those from Chlorella 5S rRNA whose sequence is revised by data included here. Various architectural features of eukaryotic 5S rRNA are summarized in terms of this secondary structural model. It is observed that previous failures to identify universal models for 5S rRNA secondary structure stem from significant differences in architecture between eukaryotic cytoplasmic and eubacterial 5S rRNAs. The usual four-helix model for eubacterial 5S rRNA secondary structure nevertheless does share several structural features with the five-helix model presented here for cytoplasmic 5S rRNA. It is thus likely that these two classes of 5S rRNA are the result of evolutionary divergence rather than convergence.
Deletion mapping of sequences essential for in vivo transcription of the iso-1-cytochrome c gene.
Authors: Faye G , Leung D W , Tatchell K , Hall B D , Smith M
Published: May 2006

The 5' termini of yeast CYC1 RNA molecules have been mapped, by nuclease S1 digestion of mRNA . DNA duplexes, to seven locations from 29 to 93 base pairs upstream from the initiating ATG codon. When the CYC1 gene is introduced into yeast in plasmid YEp13, substantially the same transcripts are made. Using this system to study in vivo gene expression, we measured the capacity of enzymatically produced DNA deletions to form the normal set of RNAs. Four regions of 5'-flanking DNA were identified as functional. Sequences within the region -242 to -139 are required for maximal CYC1 transcript formation; their deletion reduces transcription by a factor of 15 but does not change the pattern of 5' ends observed. Deletion of the sequence between -242 and -99 does not further change the overall transcript level but does affect the specificity of CYC1 mRNA starting. A deletion that extends from -242 to -75 causes both an additional shift in the pattern of 5' ends observed and a further large decrease (factor of 10--20) in CYC1 RNA level. Deletions that extend from -242 to -43, and particularly two deletions that extend still closer to the initiating ATG, cause the appearance of an abundant transcript which starts upstream of position -1078 and of minor transcripts starting in the region -325 to -245.
Non-nucleosomal packaging of a tandemly repeated DNA sequence at termini of extrachromosomal DNA coding for rRNA in Tetrahymena.
Authors: Blackburn E H , Chiou S S
Published: May 2006

A tandemly repeated DNA hexanucleotide sequence, 5'C-C-C-C-A-A3', that occurs at the termini of extrachromosomal DNA molecules coding for rRNA (rDNA) in Tetrahymena macronuclei was examined to determine whether it is packaged as nucleosomes. This repeated DNA sequence comprises the terminal few hundred base pairs at each end of the linear rDNA molecules. Digestion of macronuclei with micrococcal nuclease showed that this DNA sequence is protected from digestion but is left, following digestion, as a single but broad size class of DNA fragments several hundred base pairs long, under conditions in which bulk macronuclear DNA and rDNA were digested to fragments that were multiples of approximately 200 base pairs in length. The repeated C-C-C-C-A-A was found protected as fragments longer than the bulk macronuclear DNA digestion products at all times during digestion. Together with putative associated protein(s), this protected DNA was soluble after lysis of micrococcal nuclease-digested macronuclei at low salt concentrations but was insoluble in 0.075--0.2 M KCl, regardless of the extend of digestion. The size and solubility properties of the repeated C-C-C-C-A-A DNA nucleoprotein complex after micrococcal nuclease digestion of macronuclei are clearly distinguishable from those of nucleosomes, and it is inferred that this DNA sequence in macronuclei is packaged in chromatin by proteins other than histones.
Hemerythrin's oxygen-binding reaction studied by laser photolysis.
Authors: Alberding N , Lavalette D , Austin R H
Published: May 2006

The dioxygen--iron bond in oxyhemerythrin is shown to be photosensitive. The recombination reaction after photodissociation depends strongly on solvent viscosity. In water (eta = 1 centipoise or 1 x 10(-3) Pa . s) the recombination is monophasic and second-order in solvent oxygen concentration, with a bimolecular rate coefficient of 2.9 x 10(7) M-1 s-1. In a glycerol/water mixture (eta = 180 centipoise) a concentration-dependent geminate recombination process is also seen. This opens a class of proteins to study by flash photolysis.
Erythroid differentiation and commitment in rat erythroleukemia cells with hypertonic culture conditions.
Authors: Yamaguchi Y , Kluge N , Ostertag W , Furusawa M
Published: May 2006

Cell cultures of 7,12-dimethylbenz[a]anthracene-induced rat erythroleukemia can be stimulated to synthesize hemoglobin when cultured in hypertonic media. During hypertonic treatment the intracellular osmotic conditions immediately readjust to those of the extracellular medium. None of the Friend virus-induced mouse erythroleukemia cell lines was inducible for differentiation with the same hypertonic culture conditions used for rat cells. Earliest commitment to erythroid terminal differentiation by hypertonic treatment of cells grown in either Eagle's or Joklik's medium occurs coincident with the commitment induced by hexamethylenebisacetamide. These results make it likely that induction of differentiation in rat erythroleukemia cells is a cell membrane-mediated event.
Identification of antigenically related polypeptides at centrioles and basal bodies.
Authors: Lin W , Fung B , Shyamala M , Kasamatsu H
Published: May 2006

An antigen localized at the centriolar region has been identified by indirect immunofluorescence studies in African green monkey kidney, human, hamster, rat, and mouse cells. The antigen consists of two polypeptides of 14,000 and 17,000 daltons. A related antigen is also present at the basal body region in ciliated cells from chicken, cat, mouse, pig, steer, and rabbit trachea and from rabbit fimbria. Immunoelectron microscopy shows that the immunoreactive antigen is indeed located in the region around the basal bodies of ciliated cat tracheal cells. Thus, we have found an antigen that is common to a variety of cell types from many different animal sources and is specifically associated with both centrioles and basal bodies. The possible role of the antigen in differentiation is discussed.
Detection of phosphotyrosine-containing 34,000-dalton protein in the framework of cells transformed with Rous sarcoma virus.
Authors: Cheng Y S , Chen L B
Published: May 2006

Phosphotyrosine-containing 34,000-dalton protein is detected by treatment of a two-dimensional gel of cellular framework with 1 M NaOH at 40 degrees C for 1 hr. The alkali-resistant 32PO4-labeled 34,000-dalton protein is detected in various cell lines transformed by Rous sarcoma virus but not in lines transformed by simian virus 40, polyoma virus, herpes simplex II virus, adenovirus type 2, or chemical carcinogens. In addition, interferons or fibronectin matrices have no detectable effect on the phosphorylation of the 34,000-dalton protein in Rous sarcoma virus-transformed cells.
Identification of mitochondrial proteins and some of their precursors in two-dimensional electrophoretic maps of human cells.
Authors: Anderson L
Published: May 2006

A set of at least 30 proteins disappears from the two-dimensional electrophoretic pattern of human lymphoid cells treated with various antimitochondrial agents. This set is similar to the set of proteins found in isolated mitochondria (except for the presence of action in the latter group), indicating that the inhibitor effect stops production of a majority of mature mitochondrial proteins. Several proteins having the characteristics of precursors to the major cytoplasmically synthesized mitochondrial proteins can be observed in cells during fast-pulse experiments and in a reticulocyte lysate system fed with total lymphoid cell RNA. In the three major instances of mitochondrial precursor--product processing, the removed peptide is quite basic in each case, suggesting that a lysine- or arginine-rich terminal sequence may be necessary for initial recognition by the mitochondrial protein uptake apparatus. The inhibitor effect allows easy identification of a large set of mitochondrial proteins in two-dimensional maps of various cells, thereby specifying a particularly tractable and functionally distinctive subset of the cellular proteins. The nature and wide scope of the effect support the concept of energy-dependent "vectorial processing" [Schatz, G. (1979) FEBS Lett. 103, 203--211] and indicate that such a mechanism is generally applicable to the major class of cytoplasmically synthesized mitochondrial proteins in mammalian cells.
Structure of a rearranged gamma 1 chain gene and its implication to immunoglobulin class-switch mechanism.
Authors: Obata M , Kataoka T , Nakai S , Yamagishi H , Takahashi N , Yamawaki-Kataoka Y , Nikaido T , Shimizu A , Honjo T
Published: May 2006

An expressed gene for gamma 1 chain of MC 101 myeloma was cloned from a phage library containing partial EcoRI digests of MC 101 DNA. The cloned DNA was analyzed by restriction enzyme cleavage, Southern blot hybridization, R-loop formation, and nucleotide sequence determination. The results indicate that the expressed gamma 1 chain gene comprises at least four germline DNA segments, namely a variable-region gene, a segment of the 5' flanking region of the mu chain gene (containing J regions), a segment of the 5' flanking region of the alpha chain gene, and the gamma 1 chain gene with its flanking regions. The presence of the alpha chain gene-flanking switch (S) region (S alpha region) at the 5' side of the gamma 1 chain gene-flanking region (S gamma 1 region) indicates that the heavy chain class switch may not be mediated by stepwise linear deletion along the order of the heavy chain constant-region genes (5'-mu-gamma 3-gamma 1-gamma 2b-gamma 2a-alpha-3'). We propose a siter-chromatid exchange model that explains class switch-associated deletion of heavy chain genes by unequal crossing-over events between sister chromatids.
Gene-amplification model of carcinogenesis.
Authors: Pall M L
Published: May 2006

A two-stage model of carcinogenesis is proposed based on recent evidence for the occurrence of proto-oncogenes in the vertebrate genome, evidence for gene amplification during carcinogenesis, and studies of the action of tumor promoters. The model is baed on the view that an increase in the level of gene product from such proto-oncogenes is sufficient to induce neoplastic transformation. It proposes that the initial step in carcinogenesis (initiation) is a mutation producing a tandem duplication of a proto-oncogene. Gene amplification can then occur by successive unequal sister chromatid crossing-over events in several cell cycles until sufficient gene product is produced to transform the cell.
Antibody-mediated activation of genetically defective Escherichia coli beta-galactosidases by monoclonal antibodies produced by somatic cell hybrids.
Authors: Accolla R S , Cina R , Montesoro E , Celada F
Published: May 2006

Six hybridomas producing monoclonal antibodies against Escherichia coli beta-galactosidase (beta-D-galactoside galoctohydrolase, EC 3.2.1.23) have been derived from two separate somatic cell fusions. Three of these antibodies can activate defective enzymes produced by strains of E. coli carrying Z-gene point mutations. In antigen excess, one monoclonal antibody shows similar enzyme binding and mutant-activating capacity. Characteristically, the former reaction has a 200-fold higher equilibrium constant. These data provide direct evidence that the enzyme-activation reaction is a single-hit event in which one antibody site favors the correct conformation of one active center of the enzyme. Because each "activating" hybridoma is able to activate several but not all point mutant enzymes tested, it appears that the correction of the genetic defect is produced by binding key sites of the protein three-dimensional structure rather than the sites affected by the mutation.
Depletion of glutathione selectively inhibits synthesis of leukotriene C by macrophages.
Authors: Rouzer C A , Scott W A , Griffith O W , Hamill A L , Cohn Z A
Published: May 2006

We have examined the role of glutathione synthesis and intracellular glutathione content in the formation of leukotriene C (LTC) by mouse peritoneal macrophages. For this purpose, we utilized the drug buthionine sulfoximine (BSO), a specific inhibitor of glutathione synthesis. Thirty minutes after the addition of BSO (200 microM) to macrophage cultures, when glutathione synthesis was inhibited approximately 80%, the cells responded to a zymosan challenge with a normal release of LTC. During this period, intracellular glutathione stores were not significantly depleted. Cells exposed to BSO for 2 hr or more exhibited marked decreases in glutathione levels and a progressive inhibition of LTC synthesis. After exposure to BSO for 16 hr, intracellular glutathione was undetectable, and no LTC was synthesized by the cells. Treatment of macrophages with BSO for 16 hr had no effect on cell viability, phagocytosis, total release of arachidonic acid, or prostaglandin synthesis. However, an increased synthesis of hydroxyicosatetraenoic acids in BSO-treated cells compensated for the diminished production of LTC. We conclude that BSO produces a specific, time-dependent inhibition of LTC synthesis as a result of intracellular glutathione depletion. This is consistent with a biosynthetic pathway for LTC in which glutathione is a direct precursor of this arachidonic acid metabolite.
Thalidomide teratogenesis: evidence for a toxic arene oxide metabolite.
Authors: Gordon G B , Spielberg S P , Blake D A , Balasubramanian V
Published: May 2006

It was postulated that thalidomide causes birth defects by being metabolized to a toxic electrophilic intermediate. This hypothesis was tested by using an in vitro assay in which drug toxicity to human lymphocytes was assessed in the presence of a hepatic microsomal drug metabolizing system. Maternal hepatic microsomes from pregnant rabbits mediated the production of a metabolite that was toxic to lymphocytes. Toxicity was enhanced by inhibitors of epoxide hydrolase (EC 3.3.2.3) and abolished by adding the purified enzyme to the incubation medium. The metabolite thus appears to be in arene oxide, consistent with the previously reported isolation of phenolic metabolites of thalidomide from the urine of treated animals. Two teratogenic analogs of thalidomide (phthalimidophthalimide and phthalimidinoglutarimide) were also toxic in the system; two nonteratogenic analogs (phthalimide and hexahydrothalidomide) were not toxic, even in the presence of epoxide hydrolase inhibitors. The toxic metabolite of thalidomide was not produced by rat liver microsomes (the rat is not sensitive to thalidomide teratogenesis) but was produced by hepatic preparations from maternal rabbits, and rabbit, monkey, and human (all sensitive species) fetuses. A toxic arene oxide therefore may be involved in the teratogenicity of thalidomide.
Expression of the hepatitis B virus surface antigen gene in cell culture by using a simian virus 40 vector
Authors: Moriarty Ann M. , Hoyer Bill H. , Shih J. Wai-kuo , Gerin John L. , Hamer Dean H.
Published: May 2006

We have constructed a simian virus 40 recombinant carrying a fragment of DNA from hepatitis B virus. Cultured monkey kidney cells infected with this recombinant produce hepatitis B surface antigen. The antigen is excreted into the culture medium as 22-nm particles with the same physical properties, antigenic composition, and constituent polypeptides as those found in the sera of patients with type B hepatitis.
Sibling and parent--offspring correlation estimation with variable family size.
Authors: Karlin S , Cameron E C , Williams P T
Published: May 2006

A method for estimating intrafamilial correlations under variable family sizes involving weightings of paired data points is introduced. Classical methods of intrafamilial correlation estimation and those in current use are outlined and critically analyzed. Extensions of the proposed estimation method to more general data structures are delineated.
Tetrahydrobiopterin increases in adrenal medulla and cortex: a factor in the regulation of tyrosine hydroxylase.
Authors: Abou-Donia M M , Viveros O H
Published: May 2006

Tetrahydrobiopterin, the cofactor for tyrosine hydroxylase and other monooxygenases, is present in tissues at apparent concentrations much less than those necessary to saturate the corresponding enzymes. Reserpine treatment or insulin-induced hypoglycemia in rats produces a statistically significant increase in the tetrahydrobiopterin content of both the adrenal medulla and the cortex. Adrenal denervation and hypophysectomy selectively block the increases in cofactor level in medulla and cortex, respectively, while cycloheximide prevents the increase in both tissues. Reserpine did not increase cofactor levels in liver, kidney, or corpus striatum but decreased that of the pineal gland. These results suggest that tetrahydrobiopterin is under neural control in the medulla and hormonal control in the cortex and that increases in cofactor may result from induction of enzyme(s) in the biosynthetic pathway. These results demonstrate regulation of tissue tetrahydrobiopterin and are consistent with the suggestion that cofactor levels participate in the regulation of tyrosine hydroxylase in the adrenal medulla and may have a function, as yet undetermined, in the adrenal cortex.
Preparation of azidocalmodulin: a photoaffinity label for calmodulin-binding proteins.
Authors: Andreasen T J , Keller C H , LaPorte D C , Edelman A M , Storm D R
Published: May 2006

A photoaffinity label for calmodulin-binding proteins was prepared from 125I-labeled calmodulin (125I-calmodulin) and methyl-4-azidobenzimidate. Azidocalmodulin containing one azido group per calmodulin retained its ability to stimulate the CA2+-sensitive phosphodiesterase purified from bovine heart muscle. The concentrations of calmodulin and azidocalmodulin required for half-maximal stimulation of phosphodiesterase activity were 170 and 230 pM, respectively. Azido-125I-calmodulin was used to photoaffinity label troponin I, myosin light chain kinase, and the Ca2+-sensitive phosphodiesterase. Formation of crosslinked complexes required the presence of Ca2+ or Mn2+ and was inhibited by excess unmodified calmodulin. The calmodulin-binding subunits all formed 1:1 complexes with calmodulin, and the molecular weights of the crosslinked products obtained with troponin I, the phosphodiesterase, and myosin light chain kinase were 43,000, 79,000, and 116,000, respectively. Photolysis experiments using azido-125I-calmodulin and bovine cerebral cortex membranes or detergent-solubilized membranes resulted in formation of a limited number of specifically labeled polypeptides. Azido-calmodulin appears to be an appropriate photoaffinity label for the identification and characterization of calmodulin-binding subunits.
Internal duplication and evolution of human ceruloplasmin.
Authors: Dwulet F E , Putnam F W
Published: May 2006

With the completion of the primary structure of the 50,000- and 19,000-dalton fragments of human ceruloplasmin [ferroxidase; iron(II):oxygen oxidoreductase, EC 1.16.3.1], over half of the covalent structure of the single polypeptide chain of this protein is known. Visual and computer analysis of the sequence of the 564 amino acid residues in the two fragments gives clear evidence of statistically significant internal homology suggestive of evolutionary replication of two smaller units. Two homology regions, each composed of 224 residues, were defined by an intrasequence alignment that required only three gaps in each 224-residue segment. The two homology regions exhibited 43% identity in sequence, and 13% of the remaining positions had similar residues. The sequence of a 160-residue segment in ceruloplasmin exhibits significant homology to the active (copper-binding) sites of blue electron-transfer proteins such as azurins and plastocyanins and multicopper oxidases such as cytochrome oxidase and superoxide dismutase. It is proposed that a primitive ceruloplasmin gene was formed by the fusion of two genes coding, respectively, for protein abut 160 and 190 amino acid residues in length and that this precursor gene coding for about 350 amino acids was later triplicated to form the gene for the present-day ceruloplasmin molecule of about 1050 amino acids.
Assessment of estrogen receptor--histone interactions.
Authors: Kallos J , Fasy T M , Hollander V P
Published: May 2006

Several different in vitro binding assays show that the estrogen receptor from rabbit uterus interacts selectively with purified histones from calf thymus. The estrogen receptor binds strongly to histones H2B and H2A, moderately to histones H3 and H4, and poorly to histone H1. In the presence of histones H2B or H2A, the position at which the estrogen receptor focuses in an isoelectric gradient is shifted to a more basic zone. Kinetic experiments show that, if histone H2B is bound to a DNA, the estrogen receptor dissociates more slowly from that DNA. The portion of the estrogen receptor molecule required for binding to histone H2B is relatively stable to tryptic digestion; in contrast, the portion of the receptor molecule responsible for DNA binding is promptly lost during limited tryptic digestion. These in vitro findings suggest that the mechanism by which the estrogen receptor selectively alters gene expression may involve specific contacts with histone molecules.
A RNA helix-destabilizing protein is a major component of Artemia salina nuclear ribonucleoproteins.
Authors: Thomas J O , Raziuddin  , Sobota A , Boublik M , Szer W
Published: May 2006

A major component of 30S heterogeneous nuclear ribonucleoprotein (hnRNP) particles from Artemia salina is HD40, a protein that has been characterized as a RNA helix-destabilizing protein [Marvil, D. K., Nowak, L. & Szer, W. (1980) J. Biol. Chem. 255, 6466-6472; Nowak, L., Marvil, D. K., Thomas, J. O., Boublik, M. & Szer, W. (1980) J. Biol. Chem. 255, 6473-6478]. HD40 binds to and disrupts the secondary structure of nuclear RNA fragments isolated from 30S hnRNP with a stoichiometry of one protein per 10-12 nucleotides. The addition of HD40 in excess of this ratio results in the formation of bead-like HD4-nuclear RNA complexes that are similar in properties and appearance to native 30S hnRNP particles. The heterogeneous nuclear RNA (hnRNA) in the HD40-hnRNA complexes is unstacked and unfolded to about the same extent as the RNA in the native 30S hnRNP particles. HD40 is strikingly similar in molecular weight (40,000) and amino acid composition (no cysteine, high glycine, presence of dimethylarginine, and blocked NH2 terminus) to eukaryotic hnRNP proteins isolated from many cell types. HD40 can be separated into three isoelectric species with basic pIs, which appears to be posttranslational modifications of a single polypeptide chain.
Tandem termination sites in the tryptophan operon of Escherichia coli.
Authors: Wu A M , Christie G E , Platt T
Published: May 2006

In vivo, transcription of tryptophan (trp) operon mRNA appears to terminate at a site (trp t) 36 nucleotides after the last structural gene, and efficient function at this site requires the protein factor rho. However, distal nucleotide sequences also seem to play a role in modulating termination at trp t. We report here our in vitro studies of DNA fragments carrying portions of the trp termination region. Transcription of these DNA fragments in a purified system demonstrates that RNA polymerase actually recognizes two different termination sites. Termination at the previously characterized site, trp t, is only 25% efficient, and it is unaffected by the presence of rho factor in vitro. However, addition of rho to the transcription reaction mixture reveals that termination also occurs within a region that we have designated trp t', located about 250 bases past trp t. These two sites behave independently in vitro, whether in the tandem configuration or cloned separately, and their structural features and functional characteristics are quite different. This contrasts with the observation that termination of transcription at the end of the trp operon in vivo appears to require a rho-mediated interaction between trp t and trp t'. The possible involvement of other factors and the significance of multiple termination sites is discussed.
Apoplastic transport of ions in the motor organ of
Samanea
Authors: Campbell Neil A. , Satter Ruth L. , Garber Robert C.
Published: May 2006

Turgor-mediated leaf movements of the legume
Samanea saman
are associated with the migration of K
+
and Cl
-
between opposing sides of the motor organs (pulvini). We have investigated the pathway of this ion migration by localizing K
+
and Cl
-
within the secondary pulvinus at various times during leaf movements. Ion distributions in freeze-dried cryosections of pulvini were determined by scanning electron microscopy/x-ray microanalysis. The results indicate that the apoplast is a major pathway for the migration of K
+
and Cl
-
within the pulvinus.
Nature of the G1 phase of the yeast Saccharomyces cerevisiae.
Authors: Singer R A , Johnston G C
Published: May 2006

Under conditions that protract the S phase for Saccharomyces cerevisiae without affecting steady-state rates of cell growth or proliferation, there were striking decreases in the length of the G1 period. These decreases were localized in the period between mitosis and the start event that initiates a new cell cycle. We conclude that this major fraction of the G1 period has no functional role in the DNA-division sequence of cell cycle events.
Spontaneous tandem genetic duplications in Salmonella typhimurium arise by unequal recombination between rRNA (rrn) cistrons.
Authors: Anderson P , Roth J
Published: May 2006

A method is described to detect and measure the frequency of spontaneous tandem genetic duplications located throughout the Salmonella genome. The method is based on the ability of duplication-containing strains to inherit two selectable alleles of a single gene during generalized transductional crosses. One allele of the gene carries an insertion of the translocatable tetracycline-resistance element Tn10; the other allele is a wild-type copy of that gene. Using this technique, we have measured the frequency of tandem duplications at 38 chromosomal sites and the amount of material included in 199 independent duplications. These results suggest that, in one region of the chromosome, tandem duplications are particularly frequent events. Such duplications have end points within rRNA (rrn) cistrons and probably arise by unequal cross-over between these dispersed repeated sequences. Spontaneously duplications of this type are harbored by as much as 3% of the bacterial population. Preliminary evidence suggests that such duplications may play a significant regulatory role under conditions of rapid growth. Our analysis has suggested the position on the genome of an additional rRNA cistron.
Electrophoretically detected germinal mutations induced in the mouse by ethylnitrosourea.
Authors: Johnson F M , Lewis S E
Published: May 2006

Male DBA/2J and C57BL/6J mice were treated with ethylnitrosourea (EtNU) at a dose of 250 mg/kg of body weight. After a sterile period of 11 weeks, the treated animals were mated with untreated females; treated DBA with C57 and treated C57 with DBA. A small control group of untreated males was established, and a larger control group from earlier experiments was also used for comparison. Tissue samples removed surgically from the parents and F1 offspring were examined by electrophoresis. Nine newly arisen mutants attributable to induction by EtNU were found in 22,512 loci tested for mutation. No mutations were encountered in 290,252 control locus tests. A preliminary study conducted concomitantly with the electrophoretic analyses for dominant lethal effects and physical malformation showed no increase over background due to EtNU treatment of spermatogonia, which suggests that mutations induced by EtNU tend not to be expressed in this way. The nature of the mutants identified by electrophoresis facilitates follow-up analyses leading to increased understanding of the molecular basis and the physiological effects of induced mutations in mammalian organisms.
Identification and quantification of the rat hepatocyte asialoglycoprotein receptor.
Authors: Schwartz A L , Marshak-Rothstein A , Rup D , Lodish H F
Published: May 2006

The asialoglycoprotein receptor from rat liver was purified by solubilization and affinity chromatography on asialoorosomucoid-Sepharose. The preparation yielded four distinct polypeptides of Mr 40,000-120,000. We prepared a monoclonal antibody that both immunoprecipitates solubilized receptor activity and blocks the binding of galactose-terminal glycoproteins to immobilized receptor. The monoclonal antibody and a rabbit antireceptor antiserum immunoprecipitated all four polypeptide species. Peptide analysis by two-dimensional chromatography of the individual 125I-labeled species showed nearly identical patterns, which also suggested that the four polypeptides have a similar primary structure. To identify and quantitate the asialoglycoprotein receptor on the hepatocyte cell surface, intact cells were iodinated with lactoperoxidase, and the solubilized membranes were treated with antireceptor antibody. The Mr 55,000 and Mr 65,000 species were the major species found. Our results suggest that the Mr of the surface receptor is at least 55,000 and that it comprises between 1-2% of the iodinated hepatocyte surface protein.
Chemically synthesized peptides predicted from the nucleotide sequence of the hepatitis B virus genome elicit antibodies reactive with the native envelope protein of Dane particles.
Authors: Lerner R A , Green N , Alexander H , Liu F T , Sutcliffe J G , Shinnick T M
Published: May 2006

Thirteen peptides corresponding to amino acid sequences predicted from the nucleotide sequence of the hepatitis B surface antigen were synthesized chemically. The free or carrier-linked synthetic peptides were injected into rabbits, and 7 of the 13 elicited an antipeptide response. Antisera against four of the six soluble peptides longer than 10 amino acids were reactive with native antigen and specifically precipitated the 23,000- and 28,000-dalton forms from Dane particles. As the hepatitis molecule had not been chosen for study because of any structural feature suggesting unique opportunities for success, these results suggest that the strategy is general and should work for any protein as long as enough domains are studied. Peptides such as these could prove to be ideal vaccines.
Zinc environment and cis peptide bonds in carboxypeptidase A at 1.75-A resolution.
Authors: Rees D C , Lewis M , Honzatko R B , Lipscomb W N , Hardman K D
Published: May 2006

The structure of the metalloenzyme carboxypeptidase A (peptidyl-L-amino-acid hydrolase, EC 3.4.17.1) has been refined at 1.75 A by a restrained least-squares procedure to a conventional crystallographic R factor of 0.162. Significant results of the refined structure relative to the catalytic mechanism are described. In the native enzyme, the zinc coordination number is five (two imidazole N delta 1 nitrogens, the two carboxylate oxygens of glutamate-72, and a water molecule). In the complex (at 2.0-A resolution) of carboxypeptidase A with the dipeptide glycyl-L-tyrosine, however, the water ligand is replaced by both the carbonyl oxygen and the amino nitrogen of the dipeptide. The amino nitrogen also statistically occupies a second position near glutamate-270. Consequently, the coordination number of zinc may vary from five to six in carboxypeptidase A-substrate complexes. Implications of these results for the catalytic mechanism of carboxypeptidase A are discussed. In addition, three cis peptide bonds, none of which involves proline as the amino nitrogen donor, have been located fairly near the active site.
Mosaic nonequilibrium thermodynamics describes biological energy transduction.
Authors: Westerhoff H V , Hellingwerf K J , Arents J C , Scholte B J , Van Dam K
Published: May 2006

A procedure, called "mosaic nonequilibrium thermodynamics," for describing ion movement and energy transduction in biological membranes is tested in a model system: bacteriorhodopsin liposomes. The important steps in the theoretical derivations are summarized; one of the experimental tests of the postulated fundamental flow-force relationships is shown. Furthermore, how the quantitative method, even if used only qualitatively, facilitates analysis and understanding of experimental results (in this case, the effect of medium composition on the development of pH gradient and membrane potential in the bacteriorhodopsin liposomes) is shown. The main advantage of this method lies in its quantitative description of the effect of variation of system parameters on the performance of, in this case, the reconstituted proton pump bacteriorhodopsin. As an example, the method is shown to explain quantitatively the dependence of the steady-state pH gradient on the light intensity. Even in more refined analyses of experiments, the quantitative theoretical description is in full accordance with the experimental results; this is illustrated by considering the effect of valinomycin on the dependence of the initial rate of proton uptake into bacteriorhodopsin liposomes on light intensity. It is concluded that mosaic nonequilibrium thermodynamics describes ion movement and energy transduction in the model system of bacteriorhodopsin liposomes and, therefore, may be applied to any other biological system performing such processes.