bluuebunny/crossref_metadata_2025 huggingface dataset:
Ethylene: A Natural Regulator of Sex Expression of
Cucumis melo
L
Authors: Byers R. E. , Baker L. R. , Sell H. M. , Herner R. C. , Dilley D. R.
Published: May 2006

Sex expression in cucumber (
Cucumis sativus
L.) and muskmelon (
C. melo
L.) was correlated with endogenous ethylene production. Plants of gynoecious (all female) sex types of the two species produced more ethylene than monoecius (male-female) plants.
C. melo
plants of a gynoecious sex type that normally produce only pistillate (female) flowers, when grown with hypobaric ventilation to facilitate removal of endogenous gases by diffusion, produced perfect (hermaphroditic) flowers. When either the plant was returned to atmospheric pressure or when the reduced-pressure ventilating stream was supplemented with ethylene, the same plants produced pistillate flowers. Enrichment of the atmosphere at either normal or reduced pressure with CO
2
, a competitive inhibitor of ethylene action, also resulted in development of perfect flowers. Foliar application of a benzothiadiazole, a postulated inhibitor of ethylene action, resulted in formation of perfect flowers on gynoecious plants of
C. melo
and of staminate (male) flowers on gynoecious
C. sativus
. Based on these findings, it is proposed that ethylene is an endogenous regulator of sex expression in
C. sativus
and
C. melo
.
Elongation Factors EF Tu and EF G Interact at Related Sites on Ribosomes
Authors: Miller David Lee
Published: May 2006

The binding of elongation factor EF G to ribosomes inhibits the subsequent reaction of the ribosomes with the ternary complex aminoacyl-tRNA·EF Tu·GTP. Both the hydrolysis of GTP and the binding of aminoacyl-tRNA to ribosomes are nearly abolished by the previous binding of factor EF G to ribosomes in the presence of either fusidic acid plus either GTP or a nonhydrolyzable analog of GTP. The results suggest that each elongation factor binds to the same region on the ribosome. The GTPase activities of both factors EF G and EF Tu may be activated by interaction at the same ribosomal site, as has been previously suggested by others.
Lac
Repressor Binding to Synthetic DNAs of Defined Nucleotide Sequence
Authors: Riggs A. D. , Lin S. , Wells R. D.
Published: May 2006

Binding of
lac
repressor to 20 synthetic DNAs of high molecular weight with defined repeating sequences was investigated by competition experiments. Although none of these DNAs binds repressor as tightly as does
lac
operator, most do bind to a measurable extent. Their affinity for repressor varies greatly and is a function of both nucleotide composition and sequence. Poly(dC-dC)·poly(dG-dC) competes for repressor 200-times less well than either poly(dA-dT)·poly(dA-dT) or poly(dT-dT-dG)·poly(dC-dA-dA). The other DNAs show a broad spectrum of affinities for repressor between these extremes. These results show that the
lac
repressor has affinity for, and can distinguish between, sequences distantly related to its operator.
Molecular Basis for the Attack on Cancer
Authors: Green Maurice
Published: May 2006

Studies of cell transformation by RNA and DNA tumor viruses by DNA-RNA hybridization and extension of these techniques to analysis of human cancer tissue are reviewed. The molecular hybridization technique, it is suggested, will be useful in further studies of the role of oncogenic RNA and/or DNA viruses in causation of cancer.
Binding Proteins for an Ecdysone Metabolite in the Crustacean Hepatopancreas
Authors: Gorell Thomas A. , Gilbert Lawrence I. , Siddall John B.
Published: May 2006

When crustacean hepatopancreas is incubated in the presence of α-
3
H]ecdysone of high specific activity and is then homogenized and centrifuged, a peak of protein-radioactivity is recovered after gel filtration of the 105,000 ×
g
supernatant. Analysis of this peak by sucrose gradient centrifugation revealed the presence of two complexes of protein and labeled material (∼11.5 S and 6.35 S). The same results were obtained
in vivo
. On standing at low ionic strength, the lighter component disappeared, suggesting that the heavier component is an aggregate of the lighter one. Chemical analysis of radioactive material in the complex revealed that it is not α- or β-ecdysone nor any previously described metabolite of the ecdysones. This new metabolite of α-ecdysone is found mainly in the incubated hepatopancreas. Partial structures consistent with the analytical data are inferred for this metabolite. It is suggested that the metabolite may be active in the action of molting hormone.
Aryl Hydrocarbon Hydroxylase and Polycyclic Hydrocarbon Tumorigenesis: Effect of the Enzyme Inhibitor 7,8-Benzoflavone on Tumorigenesis and Macromolecule Binding
Authors: Kinoshita Nadao , Gelboin Harry V.
Published: May 2006

Aryl hydrocarbon hydroxylase is present and is inducible in mouse skin. 7,8-Benzoflavone, an inhibitor of the enzyme, markedly inhibits tumorigenesis by 7,12-dimethylbenz(a)anthracene, but has either no effect on or stimulates benzo(a)pyrene tumorigenesis. Thus, the role of aryl hydrocarbon hydroxylase appears highly specific for each polycyclic hydrocarbon, in respect to detoxification and/or activation of the hydrocarbon to a carcinogenic form. In parallel studies, we found that 7,8-benzoflavone significantly reduces the amount of 7,12-dimethylbenz(a)anthracene binding to mouse skin DNA, RNA, and protein, and the binding of benzo(a)pyrene to RNA and protein of mouse skin. 7,8-Benzoflavone exhibited a markedly lesser effect on the binding of benzo(a)pyrene to DNA.
Conductance in Water-Poly(vinyl alcohol) Mixtures
Authors: Komiyama Jiro , Fuoss Raymond M.
Published: May 2006

The conductance of 0.02-0.10 N potassium chloride in poly(vinyl alcohol)-water mixtures at 25° decreases by about 50% as the polymer content increases from zero to 20% by weight, while the bulk viscosity increases from 0.0089 to over 1000 poises. Further increases in polymer concentration transform the highly viscous liquid into an elastomeric solid, in which the conductance still remains relatively high; it decreases significantly only after the glass composition (75% polymer at 25°) is reached. The internal viscosity, which controls ionic mobility, was estimated from the conductance data: it ranges from 0.01 to about 0.14 over the range 0-55% polymer, similar to the viscosity of many ordinary liquids. Rates of diffusion-controlled processes involving small molecules in macromolecular media can, therefore, be expected to be similar to those in usual solution.
Antiviral Activity and Side Effects of Polyriboinosinic-Cytidylic Acid Complexes as Affected by Molecular Size
Authors: Morahan P. S. , Munson A. E. , Regelson W. , Commerford S. L. , Hamilton L. D.
Published: May 2006

The decrease of the molecular size of poly(I·C) to less than 10
6
decreases its ability to induce interferon, protect mice against virus, or enhance the immune response. Immune adjuvant activity appeared more sensitive to molecular weight than the other protective activities. The composition of the complex—the molecular size of the individual homopolymers when one was large and the other small—did not affect antiviral activity; the activity of a complex made from large poly(I) and small poly(C) was similar to one made from small poly(I) and large poly(C). Molecular size of the complex did not profoundly alter the side effects of poly(I·C). At 2 mg/kg, none of the complexes markedly altered phagocytic function. Only the largest complex sensitized the mouse to endotoxin. However, all of the complexes studied profoundly inhibited drug metabolism by the liver microsomal enzymes between 24 and 72 hr after their inoculation. Decreasing the molecular weight did not alter this inhibition.
RNA Synthesis Initiates
In Vitro
Conversion of M13 DNA to Its Replicative Form
Authors: Wickner William , Brutlag Douglas , Schekman Randy , Kornberg Arthur
Published: May 2006

Soluble enzyme fractions from uninfected
Escherichia coli
convert M13 and ϕX174 viral single strands to their double-stranded replicative forms. Rifampicin, an inhibitor of RNA polymerase, blocks conversion of M13 single strands to the replicative forms
in vivo
and
in vitro
. However, rifampicin does
not
block synthesis of the replicative forms of ϕX174 either
in vivo
or in soluble extracts. The replicative form of M13 synthesized
in vitro
consists of a full-length, linear, complementary strand annealed to a viral strand. The conversion of single strands of M13 to the replicative form proceeds in two separate stages. The first stage requires enzymes, ribonucleoside triphosphates, and single-stranded DNA; the reaction is inhibited by rifampicin. The macromolecular product separated at this stage supports DNA synthesis with deoxyribonucleoside triphosphates and a fresh addition of enzymes; ribonucleoside triphosphates are not required in this second stage nor does rifampicin inhibit the reaction. We presume that in the first stage there is synthesis of a short RNA chain, which then primes the synthesis of a replicative form by a DNA polymerase.
Repetitive Sequences in the Murein-Lipoprotein of the Cell Wall of
Escherichia coli
Authors: Braun V. , Bosch V.
Published: May 2006

The amino-acid sequence of the murein-lipoprotein of the
Escherichia coli
cell wall is presented. This protein is covalently bound to a lipid component as well as to the murein (peptidoglycan, mucopeptide). The sequence is also highly repetitive. At the N-terminal portion, there are three adjacent almost identical sequences, indicating repeated duplication of a gene coding originally for 15 amino acids. The C-terminal part of the polypeptide chain is more variable but still shows striking homology when certain sequence gaps are introduced. The lipid is bound to the N-terminal serine of the dipeptide (Ser-Ser) that extends from the repetitive sequence. At the C-terminal end where the murein is bound, a tripeptide extends from the repetitive portion. Here there are several basic amino acids and the only aromatic amino acid in the lipoprotein. The sequence is Lys-Tyr-Arg-Lys. The linkage to the murein is formed between the ε-amino group of the C-terminal lysine and the carboxyl group of the optical L-center of meso-diaminopimelic acid. The polypeptide chain is composed of 57 amino acids and lacks glycine, proline, cysteine, phenylalanine, histidine, and tryptophan. 63% of the amino acids are hydrophilic, but because of the covalently linked lipid this structural membrane protein has very hydrophobic properties.
The [unk]-Neumann Problem on (Weakly) Pseudo-Convex Two-Dimensional Manifolds
Authors: Kohn J. J.
Published: May 2006

When the Levi-form vanishes at boundary points of a pseudo-convex manifold, more delicate invariants are required to describe the function theoretic properties of the manifold. These are introduced here; the proof of the main theorem and other results, which will be described in more detail elsewhere, are described.
Significant Structure Theory of Surface Tension of the Alkali Metals
Authors: Hsu Chen C. , Eyring Henry
Published: May 2006

The volume and temperature dependence of the solid-like structure in liquids has been properly taken into account in calculations of surface tension of the liquid alkali metals. The surface tension equation derived from the significant structure theory of liquids is used. The results are quite satisfactory when compared with observed values.
Affinity Labeling of the Acetylcholine Receptor in the Electroplax: Electrophoretic Separation in Sodium Dodecyl Sulfate
Authors: Reiter Michael J. , Cowburn David A. , Prives Joav M. , Karlin Arthur
Published: May 2006

Electroplax, single cells dissected from electric tissue of
Electrophorus
, are labeled in a two-step procedure: reduction by dithiothreitol followed by alkylation by the affinity label 4-(
N
-maleimido)-α-benzyltri-[methyl-
3
H]methylammonium iodide, either alone or in combination with [2,3-
14
C]
N
-ethylmaleimide. Electrophoresis in sodium dodecyl sulfate on polyacrylamide gel of an extract, prepared with this detergent, of single-labeled or of double-labeled cells results in a major peak of
3
H activity, with a mobility corresponding to a polypeptide of molecular weight 42,000. In addition, in the double-labeled samples, there is a unique peak in the ratio of
3
H to
14
C that is coincident with the
3
H peak. The electrophoretic patterns of extracts of cells in which affinity alkylation of the reduced receptor has been suppressed by dithiobischoline, an affinity oxidizing agent, by cobratoxin, an irreversible ligand, or by hexamethonium, a reversible ligand, show a considerably diminished peak of
3
H activity in the region of molecular weight 42,000. This is the predominant difference between the electrophoretic patterns of extracts of unprotected and of protected cells. Furthermore, extracts of cells protected with dithiobischoline before labeling with both tritiated affinity label and [
14
C]
N
-ethylmaleimide do not show the peak in the
3
H to
14
C ratio seen in the absence of protection. Thus, by several diverse criteria, the peak of
3
H activity corresponding to a molecular weight of 42,000 contains affinity-labeled acetylcholine receptor or receptor subunit.
A Brain Protein Unique to the Olfactory Bulb
Authors: Margolis Frank L.
Published: May 2006

Soluble extracts from several regions of the mouse brain manifested regionally specific protein band patterns on polyacrylamide gel electrophoresis. In particular, one protein band appeared to occur uniquely in the olfactory bulb extracts where it was a quantitatively significant constituent of the soluble protein extract. This protein was purified to homogeneity by ammonium sulfate precipitation, DEAE-cellulose column chromatography, and polyacrylamide gel electrophoresis. The purified protein has a minimum molecular weight of about 20,000 by gel electrophoresis in the presence of sodium dodecyl sulfate. Precipitating antiserum prepared against this protein reacted only with the purified protein or with extracts of olfactory bulb, and not with extracts of other mouse tissues or brain regions. Quantitative immunoprecipitation assays indicate that this specific protein represents 1% of the total soluble protein in the mouse olfactory bulb. Soluble extracts of olfactory bulbs from several rodent species gave reactions of identity by agar gel diffusion with the antiserum to the mouse protein. It is suggested that this protein is an example of selective genetic expression within the central nervous system.
Amino Acid Sequence of Human apoLp-Gln-II (apoA-II), an Apolipoprotein Isolated from the High-Density Lipoprotein Complex
Authors: Brewer H. B. , Lux S. E. , Ronan R. , John K. M.
Published: May 2006

An apolipoprotein, designated by its carboxyl-terminal residue as apoLp-Gln-II, has been isolated from the human high-density lipoprotein family, and its complete aminoacid sequence was determined. The apoprotein, one of the two major apoproteins of this family, is composed of two identical polypeptide chains, each containing 77 amino acids. The two polypeptide chains are connected by a single disulfide bridge at position 6 in the sequence. The minimum molecular weight of the intact apoprotein is 17,380. The amino-terminal residue of each chain is pyrrolidone carboxylic acid, and the carboxyl-terminal residue is glutamine.
Initiation of Protein Synthesis in HeLa Cells
Authors: Chatterjee Nando K. , Kerwar S. S. , Weissbach Herbert
Published: May 2006

Initiation of protein synthesis in HeLa cells has been synchronized by exposure of the cells to fluoride. Double-labeling of such cells for short pulses with [
35
S]methionine and a tritiated amino acid, followed by Edman degradation of the puromycin-released nascent peptides, has shown that the percent of N-terminal methionine incorporated compared to total incorporation is significantly higher than the value obtained with any of the other amino acids tested. The results suggest that the bulk of the nascent proteins synthesized
in vivo
by HeLa cells are initiated with methionine.
Ribosomal RNA Synthesis
In Vitro:
A Protein-DNA Complex from
Bacillus subtilis
Active in Initiation of Transcription
Authors: Winsten Jay A. , Huang P. C.
Published: May 2006

A protein-DNA transcription complex, isolated from logarithmic-phase cells of
Bacillus subtilis
, is active in the initiation of new rounds of RNA synthesis
in vitro
. Transcription directed by the endogenous DNA of the complex is sensitive to inhibitors of initiation. In addition, the effect of addition of a competing template indicates that RNA polymerase in the complex is bound to endogenous DNA in a dissociable, preinitiation state. Hybridization-competition analysis of the RNA product obtained from the
in vitro
reaction indicates that it is greatly enriched for ribosomal RNA sequences. This initiating complex should be useful for the study of regulation of expression of ribosomal RNA genes.
Dynamics of Fluorescence Polarization in Macromolecules
Authors: Belford G. G. , Belford R. L. , Weber G.
Published: May 2006

Reexamination of the theory of fluorescence time dependence owing to rotational diffusion of rigid macromolecules reveals deficiencies or hidden restrictions in each of the previous treatments. The correct master equation has five exponential decay terms, with preexponential factors that depend upon the diffusion constants and, in a completely symmetrical fashion, upon the orientations of absorbing and emitting dipoles.
The Molecular Basis of Codominant Expression of the Histocompatibility-2 Genetic Region
Authors: Cullen Susan E. , Schwartz Benjamin D. , Nathenson Stanley G. , Cherry Marianna
Published: May 2006

H-2
alloantigens in an intact, undegraded form can be solubilized by the nonionic detergent NP-40 and isolated by indirect immunoprecipitation and electrophoresis in sodium dodecyl sulfate on polyacrylamide gels. With the use of an immunological precipitation method, the question about the number of cellular
H-2
gene products in heterozygous cells has been partially resolved. At least four separable gene products were detected in cells heterozygous at the
H-2
genetic region—one for each of the
H-2D
genes of the two parental haplotypes, and one for each of the
H-2K
genes of the two parental haplotypes. This is in contrast to the two
H-2
gene products reported previously for cells homozygous at the
H-2
region. The findings establish that the two parental
H-2
haplotypes on homologous chromosomes in heterozygous cells are ultimately expressed as different glycoprotein molecules.
Distinction between the Preneoplastic and Neoplastic State of Murine Mammary Glands
Authors: Hazlewood C. F. , Chang D. C. , Medina D. , Cleveland G. , Nichols B. L.
Published: May 2006

We have, using nuclear magnetic resonance spectroscopy, measured the relaxation times and diffusion coefficient of water protons in primary mammary adenocarcinomas of mice. In our biological model, three morphological stages were defined: (
a
) mammary gland tissue from pregnant mice, (
b
) preneoplastic nodules, and (
c
) neoplastic tissue. It was found that neoplastic tissues could be distinguished from normal and prenoeplastic tissue. Spin-spin and spin-lattice relaxation times and the diffusion coefficient of water protons are increased in the neoplastic tissue relative to mammary gland tissue from pregnant mice and preneoplastic nodule tissue.
Calcemic Fraction-A: Biosynthetic Peptide Precursor of Parathyroid Hormone
Authors: Cohn David V. , Macgregor Ronal R. , Chu Luke L. H. , Kimmel Joe R. , Hamilton James W.
Published: May 2006

Calcemic fraction-A (CF-A) is a biologically active, hypercalcemic and bone resorptive peptide, which was detected in, and isolated from, bovine parathyroid glands [Hamilton
et al.
(1971)
Endocrinology
89, 1440-1447]. It has been further purified, and its relationship to parathyroid hormone clarified. The peptide is present in fresh glands at a concentration of about 3 μg/g (parathyroid hormone, 100 μg/g). It contains 109 amino acids (hormone, 84), each of which is present in equal or greater molar ratio than in the hormone. Its molecular weight, calculated from amino-acid composition, is 12,144; determined by dodecyl sulfate-polyacrylamide gel electrophoresis, it is 12,500 (hormone, 9563). Per mole, it reacts with antiserum to parathyroid hormone to an extent of 7-10% that of the hormone, and is about 50% as active in its hypercalcemic and bone resorptive properties in the appropriate assays. Time course and pulse-chase experiments with parathyroid gland slices, in which the incorporation of amino acid into isolated peptide and hormone were measured, indicate that the hormone is made from a protein precursor; the patterns of incorporation of radioactivity are those that would be predicted from a precursor-product relationship. When the large peptide was incubated with parathyroid gland extracts it was partially converted to a molecule that appeared to be the hormone, as based upon its coelution with marker hormone from ion-exchange columns. Finally, tryptic digestion of the peptide increased the immunoreactivity of the sample in accord with the known greater immunoreactivity of the hormone than the peptide. On the basis of these results, it is proposed that the peptide is a biosynthetic precursor of the hormone in bovine parathyroid gland.
High-Resolution Shadowing of Transfer RNA
Authors: Abermann Reinhard J. , Yoshikami Doju
Published: May 2006

High-resolution shadowing with metals that melt at high temperatures was used to study macromolecules. Molecules of transfer RNA shadowed with tantalum-tungsten are readily visualized in an electron microscope. Mounting procedures for tRNA were perfected that reproducibly gave uniform distributions of both monomeric and dimeric tRNA particles, and allowed a statistical assessment of their gross shapes and sizes. Monomeric tRNA yielded a fairly homogeneous population of rod-shaped particles, with axial dimensions of about 40 × 85 Å. Dimers of yeast alanine tRNA held together by hydrogen bonds and dimers constructed by covalent linkage of the amino-acid acceptor (3′-) termini of monomers both gave slightly more heterogeneous populations of particles. Yet, their structures were also basically rod shaped, with their lengths ranging to about twice that of the monomer; this result indicates an end-to-end arrangement of the monomeric units within both dimers. These results suggest that the amino-acid acceptor terminus and the anticodon region are at the ends of the rod-shaped, dehydrated tRNA monomer visible by electron microscopy, consistent with the generally accepted view of tRNA structure in solution suggested by other workers using other methods. This study demonstrates that high-resolution shadowing with tantalum-tungsten provides a means to examine the three-dimensional structures of relatively small biological macromolecules.
Molecular Structure of the Pyruvate Dehydrogenase Complex from
Escherichia coli
K-12
Authors: Vogel Otto , Hoehn Barbara , Henning Ulf
Published: May 2006

The pyruvate dehydrogenase core complex from
E. coli
K-12, defined as the multienzyme complex that can be obtained with a unique polypeptide chain composition, has a molecular weight of 3.75 × 10
6
. All results obtained agree with the following numerology. The core complex consists of 48 polypeptide chains. There are 16 chains (molecular weight = 100,000) of the pyruvate dehydrogenase component, 16 chains (molecular weight = 80,000) of the dihydrolipoamide dehydrogenase component, and 16 chains (molecular weight = 56,000) of the dihydrolipoamide dehydrogenase component. Usually, but not always, pyruvate dehydrogenase complex is produced
in vivo
containing at least 2-3 mol more of dimers of the pyruvate dehydrogenase component than the stoichiometric ratio with respect to the core complex. This “excess” component is bound differently than are the eight dimers in the core complex.
Replicating, Covalently Closed, Circular DNA from Kinetoplasts of
Trypanosoma cruzi
Authors: Brack Ch. , Delain E. , Riou G.
Published: May 2006

When
Trypanosoma cruzi
are treated with Berenil, a trypanocide, their kinetoplast DNA contains an increased proportion of double-branched circular molecules. These replicating molecules have closed-circular template strands; their decrease in density when complexed by ethidium bromide in a cesium chloride gradient is proportional to the length of the replicated segments. Replication seems to be blocked at specific points, which are equidistantly spaced along the circular kinetoplast DNA molecules. Analysis of about 800 replicating forms showed that the lengths of the replicated branches are not distributed at random, but into several populations, which correspond to multiples of 15% of the total contour length of 0.5 μm. This distribution evokes a discontinuous replication process. The problem of whether kinetoplast DNA is synthesized by successive replication units, or whether and how Berenil might induce specific blocking of DNA replication, is discussed.
Experimental Evidence of an X-Ray Laser
Authors: Kepros John G. , Eyring Edward M. , Cagle F. William
Published: May 2006

A three-stage neodymium:glass laser has been used to produce collimated x-radiation from an aqueous copper(II) sulfate gel. The 1.06-μm Q-switch pulse from the neodymium laser was focused by a cylindrical lens to a horizontal line traversing a microscope slide sandwich that contained a thin film of gel. The emission from the gel was detected as a 0.2-mm spot on shielded, standard x-ray photographic film at distances that varied from 30 to 110 cm from the sandwich. Spot size did not increase with distance, suggesting coherence of the x-rays.
Solid-Phase Conjugation of Ferritin to Fab-Fragments of Immunoglobulin G for Use in Antigen Localization on Thin Sections
Authors: Kraehenbuhl J. P. , Jamieson J. D.
Published: May 2006

A technique for the solid-phase conjugation of ferritin to monovalent antibodies (Fab-fragments of immunoglobulin G) is described in which Fab-fragments from sheep antiserum to rabbit Fab-fragments are first adsorbed to Sepharose containing insolubilized rabbit immunoglobulin G, and subsequently allowed to couple with ferritin previously activated with toluene-2,4-diisocyanate. The conjugate, after elution from the adsorbent, is separated from free ferritin and unconjugated Fab by gel chromatography. We have used this conjugate as a common second-step reagent for the surface localization of intracellular antigens on thin sections of tissue embedded in albumin. The first-step reagent consists of specific rabbit antibodies (IgG) directed against the tissue component under study. An example of the use of this technique for the localization of trypsinogen in bovine exocrine pancreatic cells is given.
Deamidation
In Vivo
of an Asparagine Residue of Rabbit Muscle Aldolase
Authors: Midelfort Christian F. , Mehler Alan H.
Published: May 2006

Microheterogeneity of rabbit muscle aldolase is caused by deamidation
in vivo
of an asparagine residue near the C-terminus of each subunit. Isotopic labeling of a peptide containing the asparagine residue at various time intervals before isolation of aldolase permits estimation of the half-time for the deamidation as about 8 days, which is about the time estimated for the half-life of the enzyme
in vivo
. It is concluded that the aldolase as genetically determined is a tetramer, designated α
4
, that undergoes random deamidation to form α
3
β, α
2
β
2
, and αβ
3
species as intermediates in the formation of β
4
, the species in which all of the specific asparagine has been deamidated. Isoelectric focusing data indicate that the subunits do not exchange appreciably
in vivo
.
Physicochemical Characterization of Mitochondrial DNA from Pea Leaves
Authors: Kolodner Richard , Tewari K. K.
Published: May 2006

The mitochondrial DNA from pea leaves exists in a circular conformation. 25% of the circular molecules exist as supercoils, and 10% of the molecules are dimers. The molecular weight of mitochondrial DNA is about 66 to 70 × 10
6
by electron microscopy, and 74 × 10
6
from its renaturation kinetics. No evidence for inter- and intramolecular heterogeneity is found.
Activating and Protective Capacities of a Purified Electrophoretic Fraction of Murine Leukemia Virus for Murine Leukemia Virus Infectivity
Authors: Fischinger Peter J. , Lange Jens , Schäfer Werner
Published: May 2006

A highly purified gel electrophoretic fraction of murine leukemia virus (MuLV) can confer enhanced infectivity on MuLV derived from tissue culture and can protect MuLV from neutralization by specific antiserum. Of the known viral proteins tested, a purified electrophoretic fraction (14,000 daltons) is the only active fraction and seems to consist of the group-specific antigen I and an associated lipid moiety. The action of this fraction obtained from one type of MuLV is group-specific in that it can enhance and protect serologically different types of MuLV. The effect of this fraction is exerted on viruses and not on cells. MuLV derived from tumors was not enhanced by the fraction, but became amenable to its action after a single passage through tissue culture. Reconstruction experiments suggested that the fraction may consist of an exterior protein associated with some lipids. This complex, which apparently protrudes on the viral surface, is required for infectivity and shields the type-specific antigen containing the hemagglutinating site.
Conformation of Lysine Vasopressin: A Comparison with Oxytocin
Authors: Walter Roderich , Glickson J. D. , Schwartz I. L. , Havran R. T. , Meienhofer Johannes , Urry D. W.
Published: May 2006

Starting with assignments of proton nuclear magnetic resonance previously made for oxytocin in deuterated dimethylsulfoxide at 220 MHz, we have assigned resonances for the mammalian antidiuretic hormone, lysine vasopressin. The results demonstrate that spectral assignments of neurohypophyseal hormones and their congeners can, within certain limits, be derived from each other. Comparison of the spectra of lysine vasopressin and oxytocin suggests that the gross backbone conformations of their 20-membered ring components are for the most part similar in deuterated dimethylsulfoxide, whereas the C-terminal acyclic amino-acid sequence of lysine vasopressin is more flexible than that of oxytocin.
Proton Magnetic Resonance Reveals High-Spin Iron (II) in Ferrous Cytochrome P450
cam
from
Pseudomonas putida
Authors: Keller Regula M. , Wüthrich Kurt , Debrunner Peter G.
Published: May 2006

High-resolution proton nuclear magnetic resonance spectra were studied in D(+)-camphor-saturated solutions of ferric and ferrous cytochrome P450
cam
from
Pseudomonas putida
, and of the cyanide complex of ferric P450
cam
. In all these compounds several hyperfineshifted resonances of the heme group could be detected. In the ferrous protein, these resonance lines, which exhibit a Curie-type temperature dependence in the range of 5-28°, indicate the presence of high-spin iron (II). It is suggested that the iron (II) in ferrous P450
cam
might be pentacoordinated, as in other hemoproteins that can reversibly bind molecular oxygen and carbon monoxide.
Blocking by Histones of Accessibility to DNA in Chromatin
Authors: Mirsky Alfred E. , Silverman Bert
Published: May 2006

The effect of histones on accessibility of DNA to DNase in chromatin of thymus nuclei has been studied by selective extraction of either lysine-rich or arginine-rich histones. It was found that all histones block accessibility but that, weight for weight, lysine-rich histones block much more effectively than do arginine-rich histones. We point to the contrast between accessibility of DNA to DNase and of DNA to RNA polymerase, and to what may be the similarity between accessibility to DNase and DNA polymerase.
Sensitivity of the Contact Chemoreceptors of the Blowfly to Vapors
Authors: Dethier V. G.
Published: May 2006

Contact chemoreceptors on the mouthparts and legs of the blowfly
Phormia regina
that normally respond to aqueous solutions of sapid substances also respond to compounds in the gaseous state. Effective vapors include organic and inorganic acids and various unrelated nonpolar compounds. In general, the acids stimulate the salt receptor. Some nonpolar compounds stimulate the salt receptor while others inhibit it. Others stimulate the water, sugar, or “fifth” receptor. Differential action cannot be attributed to pH or solubility. Not all compounds that are irritating to mammalian mucous membranes or amphibian skin stimulate the contact chemoreceptors of the fly. Sensitivity to these vapors is a phenomenon analogous to the common chemical sense of vertebrates.
Studies on the Mechanism of Action of Nerve Growth Factor
Authors: Hier Daniel B. , Arnason Barry G. W. , Young Michael
Published: May 2006

In this study, explanted chick-embryo sensory ganglia were treated with nerve growth factor, and cellular concentrations of neurotubule protein were measured chemically by a colchicine-binding assay. Even after brief time periods, ganglia treated with growth factor were enriched in neurotubule protein, as compared with untreated (control) ganglia. Furthermore, studies with ganglia treated with both vincristine and growth factor demonstrated that neurotubule protein synthesis can occur even though neurite outgrowth is abolished. Several lines of evidence indicate that the growth factor stimulates
de novo
synthesis of neurotubule subunit protein, and that this effect precedes neurite extension. Like nerve growth factor, dibutyryl cyclic AMP also stimulates neurite outgrowth from embryonic sensory ganglia, yet it does not increase neurotubule protein levels. Available information suggests that the ability of growth factor to elicit rapid neurite outgrowth is closely related to its ability to increase cellular neurotubule levels. Cyclic AMP appears to stimulate neurite outgrowth by a different mechanism.
Estrogen-Induced Changes in Translation, and Specific Messenger RNA Levels during Oviduct Differentiation
Authors: Comstock John P. , Rosenfeld Gary C. , O'Malley Bert W. , Means Anthony R.
Published: May 2006

Estrogen-induced morphologic differentiation of chick oviduct is accompanied by increases in the total endogenous mRNA activity of oviduct polysomes. Concomitant increases are also noted in ribosome translational capacity and activity of peptide chain initiation factors. Once the differentiation process nears completion (about 7 days of estrogen administration), total ribosomebound mRNA activity decreases, but the translational machinery remains very active. In addition, estrogen induces the accumulation of ovalbumin mRNA before ovalbumin is demonstrable in the oviduct. The data suggest that the rate-limiting event in the hormonal induction of cell-specific proteins, such as ovalbumin, is the synthesis and intracellular accumulation of specific mRNA for such proteins.
Structure of Ristocetin A
Authors: Fehlner J. R. , Hutchinson R. E. J. , Tarbell D. S. , Schenck J. R.
Published: May 2006

Acid hydrolysis of ristocein A yields a number of amino acids of unusual structure. One set of diastereoisomeric pairs has a molecular weight of 362 and an empirical formula of C
17
H
18
N
2
O
7
. Mass spectral and nuclear magnetic resonance (NMR) evidence suggest a diphenyl ether with hydroxyl and α-amino acid [-CH-(NH
2
)COOH] groups on one ring, and methyl, hydroxyl and α-amino acid groups on the other ring. Coupling in the NMR and nuclear Overhauser effect experiments favor certain substitution patterns, which are shown. Another set of diastereoisomers seems to be a lower homolog of the previous set, without the aromatic methyl group.
Individual States in the Cycle of Muscle Contraction
Authors: Remedios Cristobal G. Dos , Yount Ralph G. , Morales Manuel F.
Published: May 2006

By using appropriate analogs of ATP, isometrically-held glycerol-extracted psoas fibers from rabbits are forced successively into states corresponding to molecular species in the contractile cycle. In each state measurements are made of
P
[unk], a fluorescence polarization parameter thought to relate to attitude of S-1 moieties of the myosin molecules. Also, the value of
P
[unk] is measured during active tension development. It is suggested that this value is a time-average of the
P
[unk] as S-1 moieties move through the various states of the cycle. Proposals are made concerning the sequence of states in the cycle.
The Covalent and Three-Dimensional Structure of Concanavalin A
Authors: Edelman Gerald M. , Cunningham Bruce A. , Reeke George N. , Becker Joseph W. , Waxdal Myron J. , Wang John L.
Published: May 2006

The tentative amino-acid sequence and three-dimensional structure of the lectin concanavalin A have been determined. The amino-acid sequence, which was determined chemically, contains 238 residues. The sequences of three short stretches were assigned on the basis of x-ray crystallographic data. Interpretation of an electron density map at 2-Å resolution indicates that the predominant structural element is extended polypeptide chain arranged in two anti-parallel pleated sheets or β-structures. Residues not included in the β-structures are arranged in regions of random coil. One of the pleated sheets contributes extensively to the interactions among the monomers to form both dimers and tetramers. The positions at which Mn
2+
, Ca
2+
, and saccharide are bound to the protein, and the point of cleavage for the formation of the naturally occurring fragments A
1
and A
2
, have been tentatively assigned. Both metal-binding sites are at least 20-Å removed from the position at which saccharides are bound. The saccharide-binding site is a deep pocket of approximately 6Å × 7.5Å × 18Å, the inner portion of which is occupied by hydrophobic residues.
Correlation Between Rates of Degradation of Bacterial Proteins
In Vivo
and Their Sensitivity to Proteases
Authors: Goldberg Alfred L.
Published: May 2006

Experiments were undertaken to test whether the relative rates of degradation of proteins
in vivo
might correlate with their sensitivity to proteases. Various experimental conditions that promote degradation of proteins in
Escherichia coli
increased sensitivity of average cell proteins to trypsin or other endoproteases, including incorporation of several aminoacid analogs into the proteins, incorporation of puromycin into the polypeptide chain, or frequent errors in translation. Those abnormal proteins that were degraded most rapidly within the cell appear responsible for the increased protease sensitivity of the cell extract. Normal
E. coli
proteins that rapidly turn over in growing cells are, on the average, more sensitive to trypsin or Pronase than cell proteins that turn over more slowly. The inherent sensitivity of a protein to proteolytic digestion is thus a major determinant of protein half-lives
in vivo
.
Coupling of Energy to Active Transport of Amino Acids in
Escherichia coli
Authors: Simoni Robert D. , Shallenberger Mary K.
Published: May 2006

Active transport of amino acids in isolated membrane vesicles of
E. coli
ML 308-225 is stimulated by oxidation of D-lactate, and this stimulation is dependent on electron transport [Kaback, H. R. & Milner, L. S. (1970)
Proc. Nat. Acad. Sci. USA
66, 1008]. In attempting to relate these results to amino-acid transport in intact cells, we isolated mutants of
E. coli
ML 308-225 that contain defects in D-lactate dehydrogenase (EC 1.1.2.4) and electron transport. Intact cells of these mutants are normal for transport of proline and alanine. We also isolated mutants defective in Ca,Mg-stimulated ATPase (EC 3.6.1.3), which is responsible for coupling electron transport to the synthesis of ATP. These mutants are defective in their ability to transport proline and alanine, as measured both in cells and isolated membrane vesicles. A possible role for the ATPase in coupling energy to active transport is discussed.
In Vitro
Complementation as an Assay for New Proteins Required for Bacteriophage T4 DNA Replication: Purification of the Complex Specified by T4 Genes 44 and 62
Authors: Barry Jack , Alberts Bruce
Published: May 2006

We have developed an
in vitro
complementation assay for six T4 bacteriophage gene products believed to be components of the T4 DNA replication apparatus. This assay is based upon the fact that DNA synthesis in an infected cell lysate that lacks a given gene product is specifically stimulated by addition of the missing product. By the use of such an assay, two proteins that appear to be the products of T4 genes 44 and 62 have been purified to electrophoretic homogeneity as a single complex of the two polypeptide chains.
Prevention of Simian Virus 40 Tumors by Hamster Fetal Tissue: Influence of Parity Status of Donor Females on Immunogenicity of Fetal Tissue and on Immune Cell Cytotoxicity
Authors: Girardi Anthony J. , Reppucci Phyllis , Dierlam Peggy , Rutala William , Coggin Joseph H.
Published: May 2006

Fetal tissue from primiparous hamsters prevented simian virus 40 (SV40) tumorigenesis in male hamsters, whereas fetal tissue from multiparous hamsters did not. The parity status of normal (uninoculated) hamsters also influenced the cytotoxicity of their lymphoid cells against tumor cells. Lymph node cells from nonpregnant primiparous and multiparous animals were cytotoxic in microcytotoxicity tests against SV40, polyoma, and adenovirus 7 tumor cells, but were not active against control BHK cells. Lymph node cells from virgin female donors were inactive. Peritoneal exudate cells from these donors reacted in similar fashion against SV40 tumor cells
in vitro
and in adoptive transfer tests
in vivo
. However, the cytotoxicity of peritoneal exudate cells from multiparous hamsters was greatly reduced during pregnancy, a time when noncytotoxic humoral antibody reactive with surface antigen of SV40 tumor cells is present. This humoral antibody is not detected during first pregnancy, and peritoneal exudate cells obtained from pregnant primiparous hamsters demonstrated a high degree of cytotoxicity.
A Coat Protein of the Bacteriophage M13 Virion Participates in Membrane-Oriented Synthesis of DNA
Authors: Jazwinski S. Michal , Marco Roberto , Kornberg Arthur
Published: May 2006

Several molecules of a protein specified by gene 3 of M13 comprise a minor fraction of the phage coat and have been assigned a role in adsorption to the bacterial cell. We find that the gene-3 protein molecules of the virion are fully conserved in phage that have attached irreversibly to the host cell, and they form a complex with the phage DNA when it has been converted to a duplex replicative form. In cells infected at a restrictive temperature with a thermosensitive mutant in gene 3, there is no conversion of the phage DNA to the replicative form. Both the adsorbed phage and the complex of replicative form DNA with the gene-3 protein were isolated with the inner membrane fraction of the cell. We suggest that the gene-3 protein may perform an essential function in the synthesis of replicative form by linking the phage DNA to a cellular replicative system in or on the inner cell membrane.
Mutagenic DNA Polymerase in Human Leukemic Cells
Authors: Springgate Clark F. , Loeb Lawrence A.
Published: May 2006

Evidence is presented that DNA polymerases from human leukemic cells are mutagenic. Nucleic acid-free extracts of acute lymphoblastic leukemic cells polymerized about 10-times more dCTP using poly(dA-dT)·poly(dA-dT) as a template than did extracts from normal lymphocytes. Mutagenic DNA polymerases could perhaps play an important role in tumor progression.
The Crystal Structures of 2,5-Piperazinediones Having Epipolysulfide Bridges Between C3 and C6: The Structures of
N,N
′-Dimethyl-3,6-Epitetrathio-2,5-Piperazinedione
Authors: Davis Betty R. , Bernal Ivan
Published: May 2006

The crystal and molecular structure of
N,N
′-dimethyl-3,6-epitetrathio-2,5-piperazinedione (C
6
H
8
O
2
N
2
S
4
) has been determined from three-dimensional x-ray diffraction data collected by counter techniques. The substance crystallizes in the orthorhombic space group Fdd2, with a = 15.352(5), b = 20.432(7), and c = 6.635(2) Å; V = 2081.2(8) Å
3
, D(meas) = 1.72(2) g/cm
3
, and z = 8 molecules per unit cell. The molecule lies on a crystallographic 2-fold axis, the piperazinedione ring is in the boat conformation, and the deviation from planarity is 18°. The bonds of the tetrasulfide chain alternate in length so that the S-S distances are 2.0244(9), 2.076(1), and 2.0244(9) Å. The structural data were refined by least-squares methods to an R(F) of 2.5% by use of the 1089 independent reflections (2θ ≤ 71°; MoKα) for which F
0
2
≥ 3σ (F
0
2
). Since this molecule is chemically identical with the active center of the recently isolated natural product sporidesmin G, our structural study constitutes a description of the epitetrathio-2,5-piperazinedione fragment of that molecule.
Mechanism of Protein Chain Termination: Further Characterization of a Mutant Defective in a New Protein Synthesis Factor
Authors: Ganoza M.C. , Vandermeer J. , Debreceni N. , Phillips S. L.
Published: May 2006

Mutant N4316 is conditionally lethal at 43°. At 36° it suppresses the termination codons UGA and UAA, but not the UAG codon or a missense mutant of T4 bacteriophage.
In vitro
, a factor rescues protein synthesis from a temperature-dependent arrest when N4316 extracts are used with RNA from bacteriophage f2. Analyses of the substrate in the arrested synthesis and of the product of the rescue reaction indicate that the factor works at the level of coat protein termination, and that it also affects the synthesis of noncoat protein products. The rescue factor is different from the release factors RF-1, RF-2, and RF-3. Model systems previously used to study release fail to score for at least one vital function in protein chain termination.
Regional Localization of Loci for Human
PGM
1
and
6PGD
on Human Chromosome One by Use of Hybrids of Chinese Hamster-Human Somatic Cells
Authors: Douglas George R. , McAlpine Phyllis J. , Hamerton John L.
Published: May 2006

The human gene loci
phosphoglucomutase
1
(
PGM
1
, EC 2.7.5.1) and
6-phosphogluconate dehydrogenase
(
6PGD
, EC 1.1.1.43), which are located on human chromosome one, have been assigned to a specific region of the short arm of that chromosome, by use of a hybrid cell line derived from a Chinese hamster cell line deficient in hypoxanthine phosphoribosyl transferase and a strain of human diploid fibroblasts. Cytogenetic analysis of a hybrid clone maintained for about 50 generations
in vitro
revealed two populations of cells, the first containing a human chromosome one with a break point at band 1p33, such that about 25% of the short arm of this chromosome was deleted. The second cell population contained a normal chromosome one. Biochemical analysis of subclones derived by cloning this mixed population revealed two phenotypic classes, one of which expressed all three chromosome-one markers,
PGM
1
,
6PGD
, and
peptidase C
(
Pep C
), while the other expressed only
Pep C
. Cytogenetic analysis showed that the subclones expressing all three markers carried the normal human chromosome one, while those expressing only
Pep C
carried the deleted chromosome. These data indicate that the human gene loci
PGM
1
and
6PGD
are located on the short arm of chromosome one distal to the break point, while
Pep C
lies elsewhere on the chromosome.
A Method for Detecting Pyrimidine Dimers in the DNA of Bacteria Irradiated with Low Doses of Ultraviolet Light
Authors: Ganesan Ann K.
Published: May 2006

Cells of
Escherichia coli
treated with lysozyme and Brij-58 become permeable to proteins, but do not release their DNA. I incubated permeable cells with an endonuclease that produces single-strand breaks in DNA-containing pyrimidine dimers. The enzyme entered the permeable cells, and, if they had been irradiated with ultraviolet light, caused breaks in their DNA. The frequency of breaks was estimated from the sedimentation pattern of the DNA in alkaline sucrose gradients. The procedure is sensitive enough to detect the dimers produced by a dose of 10 erg/mm
2
at 254 nm, or about 50 dimers per
E. coli
genome. This method exemplifies and extends the use of permeabilized cells for examining biological processes at the molecular level.