bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of the 3′ terminus of RNA isolated from vesicular stomatitis virus and from its defective interfering particles
Authors: Keene Jack D. , Rosenberg Martin , Lazzarini Robert A.
Published: May 2006

The 3′ termini of RNA from vesicular stomatitis virus and from three widely dissimilar defective interfering particles of the virus are PypGpU-OH. The possible relevance of these findings to autointerference and to replication of vesicular stomatitis virus is discussed.
Biochemical characterization of a mutant lipoprotein of Escherichia coli.
Authors: Wu H C , Hou C , Lin J J , Yem D W
Published: May 2006

A lipoprotein mutant of E. coli K-12 has been characterized. The mutant lipoprotein was found to differ from the wild-type lipoprotein in the following respects: (i) it is present in an appreciable amount in the soluble fraction (275,000 X g supernatant); (ii) it lacks the covalently-linked diglyceride; (iii) it contains an unmodified cysteine which can be carboxymethylated in vitro; (iv) it undergoes dimerization and the dimer can be converted into monomeric form by reduction with 2-mercaptoethanol; (v) both the monomeric form and especially the dimeric form of the mutant lipoprotein migrate more slowly than the corresponding forms of wild-type lipoprotein in sodium dodecyl sulfate/urea polyacrylamide gel electrophoresis; and (vi) the mutant lipoprotein is not assembled into the murein sacculi, and this results in a greatly reduced amount of bound-form lipoprotein in the mutant. These data strongly suggest that the mutation has affected the primary structure of lipoprotein, in such a way that it is not modified normally, leading to the production of a structurally-altered lipoprotein deficient in covalently-linked lipid as well as a defective assembly of the altered lipoprotein into the rigid layer of the cell envelope.
Gene cloning for the isolation of enzymes of membrane lipid synthesis: phosphatidylserine synthase overproduction in Escherichia coli.
Authors: Raetz C R , Larson T J , Dowhan W
Published: May 2006

We have screened a bank of 2000 E. coli strains carrying hybrid ColE1 plasmids [Clarke, L. & Carbon, J. (1976) Cell 9, 91-99] for those that correct the temperature sensitivity of a mutant in CDP-1,2-diacyl sn-glycerol:L-serine O-phosphatidyltransferase (EC 2.7.8.8, phosphatidylserine synthase). Two hybrid plasmids of this kind (pLC34-44 and pLC34-46) were identified and characterized. Strains carrying these plasmids overproduce the synthase by 6- to 15-fold, as demonstrated by assays of extracts and purification to homogeneity of the overproduced enzyme. The overproduced synthase, like the wild-type enzyme, is found associated predominately with the ribosomal fraction of crude cell extracts. Because the membrane phospholipid composition of these overproducers is not greatly altered, we suggest that the synthase is normally present in excess.
Purification of 3-hydroxy-3-methylglutaryl-coenzyme A reductase from rat liver.
Authors: Kleinsek D A , Ranganathan S , Porter J W
Published: May 2006

A procedure for the purification of 3-hydroxy-3-methylglutaryl-coenzyme A reductase [mevalonate: NADP+ oxidoreductase (CoA-acylating); EC 1.1.1.34] solubilized from rat liver microsomes is reported. This enzyme has a specific activity of 9,000-10,000 nmol of mevalonate formed per min/mg of protein. This represents a 4100-fold purification over the activity in microsomes, and a specific activity that is approximately 20-fold greater than the highest previously reported value. The enzyme is judged to be homogeneous on the basis of sodium dodecyl sulfate/polyacrylamide disc gel electrophoresis, polyacrylamide disc gel electrophoresis, and immunoanalysis. Data are also presented that indicate the separation of enzymatically active and inactive species of 3-hydroxy-3-methylglutaryl-coenzyme A reductase on affinity chromatography on a coenzyme A column.
Transmembrane movement of cholesterol in human erythrocytes.
Authors: Lange Y , Cohen C M , Poznansky M J
Published: May 2006

We studied the exchange of cholesterol between radioactively labeled plasma and human erythrocytes. Results from experiments in which [3H]cholesterol and [14C]-cholesterol were exchanged sequentially into the cells and back out into unlabeled plasma, showed that transmembrane movement of cholesterol occurred with a half-time that was either less than 50 min or greater than 10 days. To obtain further information about the transmembrane movement of cholesterol, we used a technique [Jacobson, B. S. & Branton, D. (1977) Science 195, 302-304] for exposure of the cytoplasmic surface of erythrocyte membranes. This method involved the ionic attachment of erythrocytes to derivatized glass beads followed by disruption of the cells, leaving the beads covered by membrane with the cytoplasmic surface exposed [3H]Cholesterol was exchanged into intact erythrocytes which then were attached to beads. The beads with attached membrane were incubated with phospholipid-cholesterol vesicles and the exchange of cholesterol between the membrane cytoplasmic surface and vesicles was studied. We found that [3H]cholesterol was present at the cytoplasmic surface, indicating that transmembrane movement of cholesterol had occurred within the 2.5 hr required to complete the experiment. This result suggests that the more rapid rate of transmembrane cholesterol movement, inferred from the experiments described above, is the one that applies.
Adenylate cyclase from synchronized neuroblastoma cells: responsiveness to prostaglandin E1, adenosine, and dopamine during the cell cycle.
Authors: Pénit J , Cantau B , Huot J , Jard S
Published: May 2006

Neuroblastoma cells were synchronized by a combined isoleucine plus glutamine starvation. Adenylate cyclase activity [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] was measured under basal conditions and in the presence of dopamine, adenosine and prostaglandin (PG) E1. A clear dissociation occurred between the respective evolution patterns of basal and agonist-stimulated adenylate cyclase activities. The magnitudes of the enzyme response to PGE1, adenosine, and dopamine also exhibited different evolution patterns during the cell cycle. Evolution of adenylate cyclase responsiveness to PGE1 during the cell cycle exhibited striking similarities with the intracellular 3':5'-cyclic AMP changes observed elsewhere. Use of theophylline and fluphenazine as specific inhibitors of adenosine and dopamine, respectively, made it possible to demonstrate that adenosine, dopamine, and PGE1 stimulated adenylate cyclase through independent receptor sites. Furthermore, whatever the stage of the cell cycle, responses to these three agonists were not additive, indicating that the receptors of adenosine, dopamine, and PGE1 control the same adenylate cyclase moieties. The data suggest that adenylate cyclase cell content and enzyme responsiveness to specific agonists can be independently controlled.
Molecular composition of cyanobacterial phycobilisomes.
Authors: de Marsac N T , Cohen-bazire G
Published: May 2006

Phycobilisomes isolated from eight different species of cyanobacteria contain in addition to the light-harvesting phycobiliproteins, a small number of colorless polypeptides with molecular weights higher than those of the chromopolypeptide subunits of the phycobiliproteins. In the phycobilisomes of the species examined, from four to nine colorless polypeptides were resolved by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. Those of highest molecular weight (70,000-120,000) also occurred in the washed membrane fraction of the cell and may therefore be derived from the thylakoids, to which the phycobilisomes are attached in vivo. Colorless polypeptides of lesser molecular weight (30,000-70,000) appeared to be specific constituents of the phycobilisome. In strains of cyanobacteria that adapt chromatically, their synthesis, like that of the major phycobiliproteins, is regulated by light quality.
Brain protein metabolism and the acquisition of new patterns of behavior.
Authors: Shashoua V E
Published: May 2006

Three cytoplasmic proteins (designated alpha, beta and gamma) in the goldfish brain consistently incorporated more labeled valine in animals that had acquired a new pattern of swimming behavior than in untrained animals. The changes were identified by double labeling techniques ([3H]valine injected into trained experimental animals and [14C]valine into untrained controls) and by gel-electrophoresis. Goldfish tested in a variety of control behavioral situations showed no detectable protein changes. The migration properties of alpha, beta, and gamma correspond to proteins having molecular weights of 37,000, 32,000, and 26,000, respectively. Two of the proteins (beta and gamma) were isolated, purified, and injected into rabbits. The antisera thus obtained were used: (i) to establish that the proteins are normal components of goldfish brain; (ii) to inhibit long-term retention of the behavior; and (iii) to demonstrate by immunofluorescence methods that the beta and gamma proteins are localized in certain cells at specific brain regions.
Interaction of myogenic and neurogenic mechanisms that control heart rate.
Authors: Brooks C M , Lange G
Published: May 2006

Interaction of neurogenic and myogenic factors that control heart rate was studied. Sympathetic nerve actions and stretch of the sinoatrial node both have an accelerator effect which appears to be competitive, and additive rather than facilitatory. In contrast with this, the accelerator effects of sinoatrial node stretch were proportionately greater when stretch was applied during a slowing produced by vagus nerve stimulation. The hyperpolarizing effect of vagus nerve stimulation or acetylcholine apparently potentiates the accelerator effects consquent to the depolarizing actions of stretch. The myogenic reaction can be considered as playing a role in maintaining cardiac output and preventing excessive slowing or diastolic distension and a deficient circulation.
Lipid-protein interaction in the phosphatidylcholine exchange protein.
Authors: Devaux P F , Moonen P , Bienvenue A , Wirtz K W
Published: May 2006

Incorporation of 2-acyl spin-labeled lecithin into the phosphatidylcholine protein from bovine liver results in an immobilization of the spin-label at the methyl and the carboxyl terminal end of the acyl chain. The nitroxide group on the protein-bound lecithin molecule is not accessible to ascorbate. This suggests that lecithin is buried in a pocket on the protein, which effectively shields the acyl chains from the medium.
Reconstitution of tobacco mosaic virus rods occurs bidirectionally from an internal initiation region: demonstration by electron microscopic serology.
Authors: Otsuki Y , Takebe I , Ohno T , Fukuda M , Okada Y
Published: May 2006

RNA of a common strain of tobacco mosaic virus was sequentially reconstituted first with protein of the same strain and then with protein of a tomato strain. The reconstituted particles were treated with specific antibodies against the two strain particles and were examined electron microscopically to locate the regions of rods encapsidated with the respective proteins. The results demonstrated that reconstitution starts at an internal region of the RNA about 830 nucleotides from an end that recent studies indicate to be the 3' terminus. Evidence was obtained to show that reconstitution proceeds toward the 5' terminus of the RNA until it is fully encapsidated. Encapsidation of the 3' distal portion of the RNA apparently occurs later and in a direction opposite to that of the encapsidation of the 5' distal portion.
Interaction of different egg parts in determination of various body regions in Drosophila melanogaster.
Authors: Schubiger G , Moseley R C , Wood W J
Published: May 2006

When Drosophila melanogaster embryos were ligated at very early stages of nuclear multiplication (45-60 min after egg deposition) for the entire period of embryogenesis, egg fragments of variable sizes were able to continue development up to the hatching stage. These ligated embryos differentiated larval structures; anterior fragments formed larval head and posterior fragments formed larval abdominal structures. Ligation always prevented the differentiation of some of the intermediate larval bands whereas the terminal ones were always formed. Identical results were obtained when embryos (45-60 min after egg deposition) were temporarily ligated for only 5 min. However, puncturing with a fine glass needle immediately after temporary ligation through the ligated area could give rise to complete differentiation of all the bands. Since puncturing disrupted the barrier produced by ligation, we propose that interaction between anterior and posterior egg regions is necessary to allow complete development.
Opioid peptide enkephalin: immunohistochemical mapping in rat central nervous system.
Authors: Simantov R , Kuhar M J , Uhl G R , Snyder S H
Published: May 2006

Using specific antisera to methionine-enkephalin and leucine-enkephalin, we have visualized apparent enkephalin-containing neuronal fibers and terminals throughout the central nervous system of the rat. Immunoreactive enkephalin displays sharply defined localizations. Regions of highest immunofluorescent density include the laminae I and II of the spinal cord, the substantia gelatinosa of the caudal nucleus of nerve V, the vagal nuclei of the medulla, the periventricular and periaqueductal areas of the upper medulla and midbrain, dorsomedial thalamic regions, specific hypothalamic nuclei, the basal ganglia, particularly the globus pallidus and the central nucleus of the amygdala, and the lateral septum. In certain regions enkephalin immunofluorescence corresponds closely with the distribution of autoradiographic opiate receptor grains.
Tubular presentations π of subsets of manifolds
Authors: Morse Marston
Published: May 2006

In this note the Weierstrass integral
J
is taken as
L
, the Riemann integral of length. Here

M
n
, n

> 1, is a compact, connected manifold of class
C
∞
with a positive definite Riemann structure. Presentations (φ,
U
φ
) 𝒟 ∈

M
n

and geodesics (with the aid of the Euler-Riemann equations) are defined in Morse, M. (1976) “Global variational analysis: Weierstrass integrals on a Riemannian Manifold,”
Mathematical Notes
(Princeton University Press, Princeton, NJ). Christoffel terminology is not suitable for our purposes. Conjugate points on a geodesic need a definition that does not distinguish between
simple
and
nonsimple
geodesics. Tubular
presentations
π of an open neighborhood of a geodesic lead to such a definition. These presentations are locally biunique and “compatible” with the earlier biunique presentations in 𝒟

M
n

. We shall use a presentation π in proving Theorem A below. Theorem A is essential in computing the Fréchet numbers of product manifolds as we shall show in a later paper.
Oligouridylate stretches in heterogeneous nuclear RNA.
Authors: Dubroff L M
Published: May 2006

Three classes of heterogeneous nuclear RNA (HnRNA) alpha, beta, and gamma, with different chemical and physical properties, can be identified in the early sea urchin embryo by hybridization with poly(U). The relative amounts of these classes vary as a function of embryonic development. It is demonstrated here that the adenyl-containing classes of HnRNA, alpha and beta, can be subfractionated by hybridization with poly(A)-agarose into species containing and lacking oligo(U)-enriched segments. These oligo(U) segments could not be detected in gamma HnRNA, which was previously shown to also lack adenylate segments. The relative proportions of these species undergo marked changes during development from early blastula (7 hr) to mesenchyme blastula (20 hr). I propose models to explain the possible effects of complementary sequences of adenylate and uridylate on the secondary structure of HnRNA, and speculate on the functional significance of such complexes.
Shape of the 50S subunit of Escherichia coli ribosomes.
Authors: Stuhrmann H B , Koch M H , Parfait R , Haas J , Ibel K , Crichton R R
Published: May 2006

Extrapolation of a series of low-angle neutron scattering curves to infinitely high contrast gives a scattering function IC(kappa) which is dependent on the shape of the solute molecule. For the 50S subunit of E. coli ribosomes, the first part of the structure determination by neutron scattering, namely the determination of the molecular shape from IC(kappa), is reported. The result is in good agreement with models of the 50S subunit determined by electron microscopy.
Promotion and inhibition of flower formation in a dayneutral plant in grafts with a short-day plant and a long-day plant
Authors: Lang A. , Chailakhyan M. Kh. , Frolova I. A.
Published: May 2006

Flower formation in the dayneutral tobacco (
Nicotiana tabacum
L.) cultivar “Trapezond” was accelerated by graft union with the short-day tobacco “Maryland Mammoth” when the grafts were kept on short days and by graft union with the long-day plant
N. silvestris
L. when they were kept on long days. When Maryland Mammoth/Trapezond grafts were kept on long days, flower formation in Trapezond was not, or only slightly, delayed compared to Trapezond/Trapezond controls; but when
N. silvestris
/Trapezond grafts were kept on short days, flower formation in Trapezond was inhibited and its growth changed to dwarf-like habit. The former results indicate transmission of flower-promoting material(s) (“florigen”) from photoperiodic plants maintained under flower-promoting daylength conditions to a dayneutral graft partner; the latter indicate the presence in the long-day plant
N. silvestris
under short-day conditions of potent flower-inhibiting and growth-regulating material(s) that can also be transmitted to a day-neutral partner. Analogous flower-inhibitory materials seem not to be present, or to be present to a much lesser extent, in the short-day plant Maryland Mammoth under long-day conditions.
Transformation by simian virus 40 induces virus-specific, related antigens in the surface membrane and nuclear envelope
Authors: Lin Peck-Sun , Schmidt-Ullrich Rupert , Wallach Donald F. H.
Published: May 2006

Nucleus- and mitochondrion-free membranes from hamster lymphocytes transformed by simian virus 40 (SV40), GD248 cells, cause guinea pigs to produce immune sera that reveal the presence in GD248 plasma membranes and mitochondria of two types of glycoprotein that are not detected in membranes of normal lymphocytes [Schmidt-Ullrich, R., Thompson, W. S. & Wallach, D. F. H. (1977)
Proc. Natl. Acad. Sci. USA
74, 643-647]. Indirect immune fluorescence of living, SV40-transformed T19 hamster reticulum cells, Balb/c 3T3 mouse fibroblasts, and W18 VA2 human fibroblasts, using the antisera against GD248 membrane, at 4° produced a distinct cell surface fluorescence; however, above 20°, staining at the nuclear perimeter, the SV40 U-antigen reaction, becomes equally prominent. In SV40-transformed cells that had been fixed in cold acetone, as well as in purified GD248 nuclei, thermostable U-antigen staining is dramatic, but there is no reaction for nuclear T-antigen. Rabbit antisera against T19 cells gave immunofluorescence reactions equivalent to those obtained with the antisera against GD248 cells. Normal guinea pig or rabbit sera and cells that had not been transformed by SV40 gave no reaction. Our sera from tumor-bearing hamsters gave only nuclear T-antigen fluorescence. The results indicate the presence of related, SV40-specific antigens in the surface membranes, nuclear envelope, and possibly other intracellular organelles of SV40-transformed cells.
Selective amplification of genes on the R plasmid, NR1, in Proteus mirabilis: an example of the induction of selective gene amplification.
Authors: Perlman D , Stickgold R
Published: May 2006

The drug-resistance plasmid, NR1, is a 37-micron circular DNA molecule that contains two components: the resistance transfer factor (29 micron) carrying the transfer genes and the genes for tetracycline resistance, and the r-determinant (8 micron) carrying the genes for resistance to several other antibiotics including chloramphenicol (Cm). In Proteus mirabilis, these two components are capable of independent replication, or they may replicate as a composite molecule. When cells of P. mirabilis containing NR1 are cultured in medium containing Cm at 250 microgram/ml a growth lag of 20-35 hr ensues. During this lag, Cm induces the selective amplification of the r-determinant, including the gene for resistance to Cm. The amplification results from the excision of the r-determinant from the R plasmid, the independent replication of the r-determinant to give polymeric as well as monomeric r-determinants, and the eventual reintegration of multiple tandem copies of the r-determinant with the resistance transfer factor to form a new R plasmid with multiple copies of the r-determinant. This mechanism represents a new level of control of gene expression in bacterial systems--namely, the induction of selective gene amplification.
Ligands and oxidants in ferrihemochrome formation and oxidative hemolysis
Authors: Itano Harvey A. , Hirota Kazuhiro , Vedvick Thomas S.
Published: May 2006

We have investigated the effect of size of a single neutral ring substituent on the induction of hemolytic anemia and the formation of a ferrihemochrome by substituted phenylhydrazines. The severity of induced anemia decreased with increase in size of a halogen atom or an alkyl group
ortho
to the hydrazino group, little anemia resulting from 2-iodophenylhydrazine and no anemia from 2-
tert
-butylphenylhydrazine. The size of a halogen atom or an alkyl group at the
meta
or
para
position had relatively little effect on the severity of induced anemia. The ability of an arylhydrazine to induce hemolytic anemia paralleled its ability to produce a ferrihemochrome with an exogenous ligand, probably the corresponding aryldiazene. In general, rapid and complete formation of ferrihemochrome occurred with arylhydrazines that induced severe anemia. The degree of hemolysis induced by an arylhydrazine was not related to its rate of autooxidation, i.e., the rate at which oxidants are formed by the reduction of oxygen. We propose a mechanism of arylhydrazine-induced oxidative denaturation based on the simultaneous formation of hydroxyl radical and aryldiazene ferrihemochrome in a reaction of oxyhemoglobin with arylhydrazine. We suggest that after oxidation of the porphyrin ring is initiated by a hydroxyl radical, oxidative cleavage of the ring is facilitated by the presence of a large ligand in the heme crevice. Thus, aryldiazene ferrihemochrome may contribute to instability in a hemoglobin molecule, whereas globin ferrihemochrome results from instability.
Single partition function for three phases
Authors: Ma Shao-mu , Yoon Y. H. , Lee S. T. , Eyring Henry
Published: May 2006

The significant structures theory of liquids has been extended to take into account (
i
) translational degrees of freedom in the degeneracy term and (
ii
) the perturbation term which becomes important near the critical region. With these improvements, the calculated thermodynamic properties of argon agree very well with experimental results from the melting point through the critical point, along the coexistence curve as well as along the critical isochore and for the solid and the vapor.
Arrangement of water molecules in cavities and channels of the lattice of [Phe4Val6]antamanide dodecahydrate.
Authors: Karle I L , Duesler E
Published: May 2006

The synthetic, biologically active, [Phe4Val6] analog of natural antamanide has been crystallized from a solution containing calcium nitrate, acetone, and acetonitrile. The crystal does not contain any Ca2+ ions but does contain 12 water molecules per peptide molecule. The conformation of this dodecahydrate is identical to the trihydrate crystallized from n-hexane/methyl acetate. The packing in both crystals is very similar, governed by parallel bands of phenyl and pyrrolidine ring stacking and by continuous channels for the solvement molecules, water in this case and n-hexane/methyl acetate in the previous study. The two structures are not ideally isomorphous, since the c cell parameter differs by more than 1.0 A in the two cells. There are three functions for H2O molecules: the three intrinsic H2O molecules in the interior of the peptide ring, the H2O bound to the exposed C=O groups, and the H2O molecules that fill space in the solvent channels. There are no direct hydrogen bonds between neighboring peptide molecules and there are only two intramolecular NH-O=C bonds (of the 5 leads to 1 type).
Expression of petite mitochondrial DNA in vivo: zygotic gene rescue.
Authors: Strausberg R L , Butow R A
Published: May 2006

A protocol is introduced for probing the organization and regulation of expression of the yeast mitochondrial genome, termed "zygotic gene rescue." The procedure is based on the notion that genes retained on mitochondrial DNA of on the notion that genes retained on mitochondrial DNA of petites can be expressed in zygotes of a cross between petite and wild type. To test the validity of this notion, we have taken advantage of our ability to discriminate, by mobility differences on sodium dodecyl sulfate/polyacrylamide gels, different forms of the product of alleles of the mitochondrial gene, varI. In petite strains that have retained the varI gene, its characteristic product appears in zygotes 4-5 hr after mating; no product is observed in petite strains deleted in the varI locus. Our studies indicate that (i) expression in the zygote of the varI gene in the petite genome is not exclusively the result of recombination with mitochondrial DNA of the wild-type tester, and (ii) the varI gene is probably reiterated in the petite mitochondrial genome. The strength of the technique of zygotic gene rescue in the analysis of the mitochondrial genome is discussed.
Binding of Zn2+ to rat liver fructose-1,6-bisphosphatase and its effect on the catalytic properties.
Authors: Pedrosa F O , Pontremoli S , Horecker B L
Published: May 2006

Rat liver fructose-1,6-bisphosphatase (D-fructose-1,6-bisphosphate 1-phosphohydrolase, EC 3.1.3.11) contains 12 binding sites for Zn2+ per molecule, or 3 per subunit, as determined by gel filtration and by precipitation of an insoluble Zn2+-enzyme complex. The first set of sites binds Zn2+ with very high affinity, and the binding constant for these sites could not be determined. The average values of the dissociation constants for the second and third sets of sites were approximately 0.4 and 1.5 muM, respectively. The third set of sites, having lowest affinity, appears to be identical to the binding sites for the activating cation, Mg2+, and the binding of Zn2+ to this set of sites is prevented by the addition of Mg2+. Binding of the first 4 equivalents of Zn2+ yields an enzyme of intermediate activity, while the binding of 8 equivalent results in almost complete inhibition of catalytic activity. Thus Zn2+ appears to function as both an activator and a negative allosteric regulator of fructose-1,6-bisphosphatase activity.
Molecular weight of bacteriorhodopsin solubilized in Triton X-100.
Authors: Reyenolds J A , Stoeckenius W
Published: May 2006

Bacteriorhodopsin from Halobacterium halobium has been solubilized in the nonionic detergent Triton X-100. The circular dichroic spectrum and hydrodynamic properties indicate that the structure of this protein in the detergent is not significantly altered from that of the native membrane-bound form. Bacteriorhodopsin is monomeric under the conditions of solubilization with a molecular weight of 24,250+/-2,000 and binds approximately one micelle of Triton X-100.
Histones: metabolism in simian virus 40-infected cells and incorporation into virions.
Authors: Tan K B
Published: May 2006

The infection of confluent monkey cells with simian virus 40 induced the synthesis of both cellular DNA and histones. However, during the course of infection, cellular histone synthesis was uncoupled from cellular DNA replication and became coupled to viral DNA replication. The synthesis of all five host histone species was induced after virus infection and they appeared to be more highly phosphorylated than their couterparts in uninfected cells. At late times after infection, the cells contained twice as much histones as did uninfected cells. All the histone species except H1 were incorporated into virions. Compared to cellular histones, virion histones were enriched in the arginine-rich species H3 and H4. Although both old and newly synthesized cellular histones were incorporated into virions, there were about 5 times more newly synthesized than old histone polypeptides in virions.
Structural convergence during protein evolution.
Authors: Salemme F R , Miller M D , Jordan S R
Published: May 2006

Several recent protein crystallographic structure determinations have demonstrated the existence of considerable tertiary structural similarity among proteins otherwise having little similarity in either amino acid sequence or biological function. In order to assess the possibility that such proteins may have arisen through processes of divergent evolution from a common ancestor, a graphical presentation is given which correlates the pattern of allowed single base substitutions defined by the genetic code with the associated changes in the structural properties of the encoded amino acids. The results show that while a large degree of structural conservation is evident due to codon synonomy, there is, in general, little tendency for the code to be structurally conservative in the majority of the cases where codon single-base changes result in amino acid substitutions. The possible consequences of this pattern of potential amino acid substitutions are discussed in relation to protein evolutionary processes.
Isolation of folded chromosomes from the yeast Saccharomyces cerevisiae.
Authors: Piñon R , Salts Y
Published: May 2006

Two fast-sedimenting chromatin complexes with sedimentation velocities of approximately 4600 and 3000 S can be isolated from logarithmically growing diploid Saccaromyces cerevisiae cells. The DNA in both structures appears to be folded into at least 60 domains and characterized by a negative superhelical density. Sensitivity to proteases and insensitivity to RNases suggest that proteins and not RNA are important in maintaining the organization of the chromosomes in both structures. The 46000S and 3000S complexes represent folded genomes isolated from diploid cells in the G2 and G1 stages of the cell cycle, respectively.
Topographic separation of adenylate cyclase and hormone receptors in the plasma membrane of toad erythrocyte ghosts
Authors: Sahyoun N. , Hollenberg M. D. , Bennett V. , Cuatrecasas P.
Published: May 2006

Brief sonication of whole erythrocyte plasma membranes (ghosts) from toads at 4° does not inactivate adenylate cyclase [ATP pyrophosphate-lyase (cyclizing); EC 4.6.1.1] or destroy the receptor binding properties of hydroxybenzylpindolol or insulin. The hormonal (but not the fluoride-induced) stimulation of this enzyme is, however, lost. Fractionation of the small, resealed membrane fragments (vesicles) on discontinuous sucrose gradients results in the separation of vesicle populations differing grossly in size and protein composition. In addition, the distribution of the β-adrenergic receptor, an insulin binding site, and adenylate cyclase among these vesicles fractions differs. The pattern of distribution of these functional structures can be altered differentially by manipulations of the ghosts before sonication. For example, brief preincubation with isoproterenol leads to a change in the relative distribution of β-receptor (but not adenylate cyclase) among the various vesicle fractions; this effect is not obtained with β-receptor antagonists, which block the isoproterenol effect. Exposure of the ghosts to different temperatures, changes in the divalent cation composition of the medium, or the addition of ATP also leads to changes in the distribution of surface markers of the subsequently formed vesicles. The results indicate gross asymmetries in the distribution of protein components within the plane of the membrane and raise important questions regarding the manner whereby functionally related and coupled components, such as hormone receptors and adenylate cyclase, interact.
Independent expression of the adrenergic phenotype by neural crest cells in vitro.
Authors: Cohen A M
Published: May 2006

Neural crest cells obtained from Japanese quail and grown in vitro without other embryonic tissues differentiate into adrenergic cells. These cells show intense catecholamine-specific histochemical fluorescence, and some have long, varicose neuronal processes. Ultrastructural examination shows two populations of cells, one with small (about 90 nm) dense-core vesicles resembling principal sympathetic neurons and the other with larger (about 150 nm) dense-core granules resembling chromaffin or small intensely fluorescent cells. Neuronal cells without adrenergic characteristics are also present. These results are compatible with the hypothesis that a population of cells determined along neuronal lines exists in the neural crest prior to migration.
Mobility and distribution of a cell surface glycoprotein and its interaction with other membrane components
Authors: Schlessinger J. , Barak L. S. , Hammes G. G. , Yamada K. M. , Pastan I. , Webb W. W. , Elson E. L.
Published: May 2006

Fluorescence photobleaching recovery and immunofluorescence methods have been used to study the lateral mobility and topographical distribution of a major cell surface glycoprotein (CSP). Both endogenous CSP and fluorescent-labeled exogenous CSP bind to the cell surface in a fibrillar pattern and are immobile on the experimental time scale. Azide, vinblastine, and cytochalasin B do not alter the immobility and cell surface distribution of the CSP molecules. Therefore, oxidative phosphorylation and the cytoskeleton do not seem to be responsible for the properties of the bound glycoprotein. The presence of immobile CSP fibrils does not, however, impede the diffusion of a lipid probe, a ganglioside analogue, or various surface antigens. Therefore, the fibrils apparently do not form a “barrier” across the lipid phase of the plasma membrane. In contrast, concanavalin A binds to CSP and is largely immobile in regions rich in CSP. The presence of immobile concanavalin A receptors in areas or on cells lacking CSP indicates that other types of immobile concanavalin A receptors also exist.

CSP does not bind to lipid bilayers composed of phosphatidylcholine or oxidized cholesterol. It does bind to dextran-coated bilayers as a diffuse distribution of mobile molecules that can patch after addition of antibodies to CSP. The latter result suggests that CSP molecules do not interact strongly with other CSP molecules under these conditions. Exogenous CSP binds to regions on the cell surface that already bear CSP. In view of the apparent weakness of CSP-CSP interactions on the lipid bilayer, it seems possible that the assembly of CSP fibrils is nucleated by cell surface components in addition to CSP.
Recombinant plasmid that carries part of the nitrogen fixation (nif) gene cluster of Klebsiella pneumoniae.
Authors: Cannon F C , Riedel G E , Ausubel F M
Published: May 2006

We have cloned fragments of the Klebsiella pneumoniae genome that carry part of the his operon and part of the nitrogen fixation (nif) gene cluster on the amplifiable plasmid pMB9. One particular plasmid, pCRA37, complements mutations in the hisD, nifB, and nifF loci. The physical map of pCRA37 as determined by restriction enzyme analysis correlates with the genetic map of the his-nif region as determined previously by phage P1-mediated cotransductional analysis.
Simultaneous deletion of D-alanine carboxypeptidase IB-C and penicillin-binding component IV in a mutant of Escherichia coli K12.
Authors: Iwaya M , Strominger J L
Published: May 2006

Mutants of Escherichia coli with much decreased activity of D-alanine carboxypeptidase (peptidyl-D alanine hydrolase, EC 3.4.12.11) were found among E. coli K12 extensively mutagenized with nitrosoguanidine treatment by assaying individual colonies for the enzyme activity. One such mutant with only 10-12% residual activity was characterized extensively. The soluble carboxypeptidase activity (corresponding to D-alanine carboxypeptidase IC of Tamura T., Imae, Y. & Strominger, J.L. [(1976) J. Biol. Chem. 251, 414-423] was deleted. This enzyme activity in the particulate fraction was markedly reduced but transpeptidase activity was normal. However, penicillin-binding component IV was deleted from the particulate fraction. Both the physiology and penicillin sensitivity of the organism were relatively normal, except that mutant cells were markedly more stable to penicillin-induced lysis, suggesting the possibility that carboxypeptidase IC really functions as an endopeptidase. The possible relationship of the deleted carboxypeptidase activity and the deleted penicillin binding component are discussed.
Common precursor to corticotropins and endorphins
Authors: Mains Richard E. , Eipper Betty A. , Ling Nicholas
Published: May 2006

Double-antibody immunoprecipitation procedures with antisera to endorphins and to corticotropin (ACTH) were used to study the biosynthesis of these peptides in a mouse pituitary tumor cell line. Cultures were incubated with a
3
H-labeled amino acid, and aliquots of culture medium were immunoprecipitated. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis of [
3
H]phenylalanine-labeled immunoprecipitates prepared with endorphin antisera resolved three forms of endorphin with apparent molecular weights of 31,000, 11,700, and 3500; immunoprecipitates prepared with the ACTH antiserum contained four forms of ACTH with apparent molecular weights of 31,000, 23,000, 13,000 and <4500. Sequential immunoprecipitation of culture medium with the ACTH antiserum and then with the endorphin antiserum (or the reverse order) indicated that both antisera precipitated the same 31,000 dalton molecule. Purified pools of the different forms of ACTH and endorphin were prepared by immunoprecipitation and gel filtration. The tryptic peptides found in [
3
H]phenylalanine- or [
3
H]tryptophan-labeled 31,000 dalton ACTH were identical to the tryptic peptides found in digests of 31,000 dalton endorphin labeled with the same amino acid. A tryptic peptide similar to the lipotropin tryptic peptide [βLPH(61-69)] that contains the opiate-active methionine-enkephalin sequence could be identified in 31,000 dalton ACTH and in all the different forms of endorphin. Most of the peptide cleaved from 31,000 dalton ACTH when it is converted to 23,000 dalton ACTH could be precipitated by endorphin antisera; this 11,700 dalton endorphin molecule is similar to the pituitary hormone βLPH in size and structure. The 3500 dalton endorphin is similar to β-endorphin in size and structure. The culture medium from the AtT-20 mouse pituitary tumor cells contained approximately equimolar amounts of ACTH-related peptides and endorphin-related peptides.
In vitro
and
in vivo
correlation of clotting protease activity: Effect of heparin
Authors: Gitel Sanford N. , Stephenson Ronald C. , Wessler Stanford
Published: May 2006

The thrombogenicity of three highly purified proteases (thrombin, activated Factor X, and activated Factor IX) was determined quantitatively in an animal model. The minimal amounts required to produce a standard score 4 thrombus were 1.1 nmol for thrombin, 0.12 nmol for activated Factor X, and 0.018 nmol for activated Factor IX. After the administration of heparin at 5, 10, and 20 units/kg in rabbits, the thrombogenicity of each of these proteases decreased progressively. The heparin-induced inhibition of thrombosis decreased in the order, activated Factor IX > activated Factor X > thrombin at each heparin concentration. These differences were statistically significant.

These
in vivo
data provide support for the following hypotheses originally developed from
in vitro
experiments: (
i
) activation of the blood coagulation system, which proceeds through a cascade mechanism, incorporates biochemical amplification; (
ii
) the inhibition of activated Factor IX by antithrombin III in the presence of heparin is an important reaction in the prevention of thrombosis; (
iii
) less heparin is required to inhibit thrombosis prior to thrombin generation than afterward; (
iv
) an increase in the reactivity of antithrombin III reflects a decreased tendency to thrombosis while a decrease in this reactivity reflects an increased tendency to thrombosis.
Lithium efflux through the Na/K pump in human erythrocytes
Authors: Dunham Philip B. , Senyk Oksana
Published: May 2006

Active Li efflux from human erythrocytes was shown to be mediated by the Na/K pump: (
i
) intracellular Li (Li
c
) activated ouabain-sensitive K influx, and (
ii
) a portion of the Li efflux required external K and was inhibited by ouabain. In activating K influx, Li
c
interacts with the pump like Na rather than like K—depleting the cells of orthophosphate inhibited activation of K influx by intracellular K (K/K exchange) but did not inhibit Li-activated K influx. (To show these interactions of Li
c
with the Na/K pump,
p
-chloromercuribenzenesulfonate or nystatin was used to allow replacement of intracellular Na and K with Li and choline.) From kinetic studies of the pump, it was shown that the apparent affinity of the intracellular aspect of the Na/K pump for Li was an order of magnitude less than that for Na. From simultaneous measurements of ouabain-sensitive net fluxes of Li and K in Na-free cells, it was shown that the pump-mediated K influx and Li efflux were coupled. The stoichiometry of the coupling ratio was close to 1:1 for Li:K, different from the coupling ratio of 3:2 for Na:K in the pump's normal mode of operation. It had been shown previously that the Na/K pump in human erythrocytes mediates active Li influx. Because it also mediates active Li efflux, the molecular mechanisms for distinguishing between Na and K must be qualitatively different at the internal and external aspects of the pump. The possible relevance of the results of this study to manic depressive illness and Li therapy is discussed.
Primary structure of human C-reactive protein.
Authors: Oliveira E B , Gotschlich E C , Liu T Y
Published: May 2006

The complete amino acid sequence of human C-reactive protein has been established. Distant homologies to C3 homology region in the CH2 domain of IgG and to C3a anaphylotoxin have been noted. No homology to other immunoglobulin homology regions or to the same homology region in other heavy chains was observed. The previously reported homologies between rabbit and human C-reactive protein and protein C1t have been extended and strengthened.
Fatty acid synthetase from Brevibacterium ammoniagenes: formation of monounsaturated fatty acids by a multienzyme complex.
Authors: Kawaguchi A , Okuda S
Published: May 2006

A multienzyme fatty acid synthetase complex isolated from Brevibacterium ammoniagenes has been purified to a specific activity of 1440 nmol of malonyl-CoA incorporated per min/mg. The enzyme is homogeneous, as judged by gel electrophoresis on agarose gels, and has a molecular weight of 1.2 X 10(6). Both NADPH and NADH are required for activity. In contrast to other fatty acid synthetase complexes, the enzyme catalyzes the synthesis of both long-chain saturated and monounsaturated fatty acids from malonyl-CoA and acetyl-CoA. The formation of unsaturated fatty acids is oxygen-independent and sharply reduced by 3-decynoyl-N-acetylcysteamine, a known inhibitor of Escherchia coli beta-hydroxydecanoyl thioester dehydrase (EC 4.2.1.60).
Nucleotide phosphotransferase of Escherichia coli: purification by affinity chromatography.
Authors: Brunngraber E F , Chargaff E
Published: May 2006

Improved extraction and purification procedures permit the isolation from Escherichia coli W cells of much larger quantities and of more highly purified preparations of nucleotide phosphotransferase. Of various affinity resins tested for efficiency of purification, columns of agarose/5'-AMP (AGAMP), type 3, proved the best. In this way a 300- to 450-fold purification of the enzyme was achieved in a few steps. The enzyme, which, as reported before, transfers organically bound phosphate to the 2' or 3' hydroxyls of nucleosides and nucleotides, was tested in its behavior toward a series of ribonucleosidonucleotides, namely, CpC, ApA, CpA, and ApC. All were phosphate acceptors, but a detailed comparative study of adenosine and cytidine, 5'-AMP and 5'-CMP, and ApA and ApC revealed peculiar specificities in the relative distribution of the phosphorylated products.
Frog oocytes synthesize and completely process the precursor polypeptide to virion structural proteins after microinjection of avian myeloblastosis virus RNA.
Authors: Ghysdael J , Hubert E , Trávnícek M , Bolognesi D P , Burny A , Cleuter Y , Huez G , Kettmann R , Marbaix G , Portetelle D , Chantrenne H
Published: May 2006

After microinjection of Xenopus laevis oocytes with RNA from avian myeloblastosis virus, viral structural proteins p27, p19, p15, and p12 are formed by a sequence of posttranslational cleavages of a high-molecular-weight precursor polypeptide. The 60-70S RNA aggregate or its 30-40S RNA subunits obtained by heat or formamide treatment possess the same ability to serve as template in X. laevis oocytes. The processing pattern of virus-specific precursor polypeptides is the same in X. laevis oocytes as in chick embryo fibroblasts infected with avian myeloblastosis virus, but the processing takes place at a much slower rate.
Conformation of beta-endorphin and beta-lipotropin: formation of helical structure in methanol and sodium dodecyl sulfate solutions.
Authors: Yang J T , Bewley T A , Chen G C , Li C H
Published: May 2006

Circular dichroic spectra of camel beta-endorphin and ovine beta-lipotropin in water show little, if any, secondary structure. Intrinsic viscosities and sedimentation coefficients of the two peptides also suggest that the molecules are not compact and globular. Methanol or sodium dodecyl sulfate promotes the formation of helical structure to an extent as much as one-half of either peptide molecule. The conformation of the complex between camel beta-endorphin and dodecyl sulfate may be related to the opiate-like function of this peptide hormone.
5'-Terminal 7-methylguanosine and mRNA function: influence of potassium concentration on translation in vitro.
Authors: Weber L A , Hickey E D , Nuss D L , Baglioni C
Published: May 2006

Vaccinia mRNAs containing either 5'-terminal m7G or unmethylated 5'-terminal structures were synthesized in vitro and their relative efficiencies of translation were compared in wheat germ and reticulocyte cell-free protein-synthesizing systems. The importance of the m7G group for efficient translation increases as the K+ concentration is raised. At K+ concentrations optimal for translation of mRNA containing m7G, unmethylated mRNA is translated at the same relative low efficiency in both cell extracts. The rate of binding of mRNA to ribosomes at K+ concentrations close to those found in intact cells is strongly influenced by the presence of m7G regardless of the source of the cell extract.
Packaging recombinant DNA molecules into bacteriophage particles in vitro.
Authors: Hohn B , Murray K
Published: May 2006

Recombinant phage genomes made in reactions with purified enzymes may be recovered directly by packaging into phage heads in vitro. The process is efficient and nonselective and offers containment in initial stages of handling recombinant DNA. Ligase [poly(deoxyribonucleotide):poly-(deoxyribonucleotide) ligase (AMP-forming), EC 6.5.1.1] reaction products can recombine with endogenous phage DNA during packaging, but UV-irradiation eliminates the biological activity of the endogenous DNA.