bluuebunny/crossref_metadata_2025 huggingface dataset:
Tetrahedral Iron in the Active Center of Plant Ferredoxins and Beef Adrenodoxin
Authors: Eaton William A. , Palmer Graham , Fee James A. , Kimura Tokuji , Lovenberg Walter
Published: May 2006

The coordination structure of the iron-sulfur complex in spinach ferredoxin and adrenodoxin is investigated by optical spectroscopy. The circular-dichroism and absorption spectra of these two-iron iron-sulfur proteins reveal weak electronic transitions in the near-infrared wavelength range, 0.8-2.5 μm (12,500-4000 cm
-1
). On the basis of the low absorption intensities and large anisotropy factors,
d
→
d
transitions of the iron can be identified in the reduced proteins at about 4000 cm
-1
and 6000 cm
-1
. The low energy of these one-center ligand-field transitions, together with the similarity to the ligand-field spectrum of the one-iron protein rubredoxin, leads to the conclusion that the reduced two-iron iron-sulfur proteins also contain a high-spin ferrous ion in a distorted tetrahedral site.
Regulation of the Nucleolar DNA-Dependent RNA Polymerase by Amino Acids in Ehrlich Ascites Tumor Cells
Authors: Franze-Fernández M. T. , Pogo A. O.
Published: May 2006

Experiments were performed to ascertain the degree to which the amount of amino acids might be one of the regulatory factors that control the activity of the nucleolar RNA polymerase. Assays of the enzymatic activity were done with isolated nuclei from cells incubated with low and high concentrations of amino acids. Soon after the cells were exposed to a medium enriched in amino acids, a rapid increase of nucleolar RNA polymerase activity occurred. A similar result was obtained in cells incubated with lower concentrations of amino acids. However, the rate of ribosomal RNA synthesized was regularly much higher in cells incubated in a medium enriched with amino acids than in a medium low in amino acids. Apparently, the amino acids only controlled ribosomal RNA synthesis. Thus, neither maturation, processing, and transport of nuclear precursors into cytoplasmic ribosomal RNA, nor the synthesis of rapidly labeled RNA was affected.
Inhibition or Enhancement of Immunological Injury of Virus-Infected Cells
Authors: Brier Arnold M. , Wohlenberg Charles , Rosenthal Joel , Mage Michael , Notkins Abner Louis
Published: May 2006

Within hours after infection of cells with herpes simplex, vaccinia, influenza, or Newcastle disease virus, new antigens appeared on the surface of infected cells. The interaction of specific antiviral antibody and complement with these antigens resulted in cell destruction, which was quantitated by the release of
51
Cr. A number of factors can influence the degree of cell destruction, including the density of viral antigens on the surface of infected cells, the nature of the antiviral antibody, and the presence of anti-immunoglobulins. The immunological destruction of virus-infected cells may on the one hand serve as a defense mechanism against certain viral infections, while on the other hand it may contribute to the pathology of the host.
Analysis of DNA Polymerases II and III in Mutants of
Escherichia coli
Thermosensitive for DNA Synthesis
Authors: Gefter Malcolm L. , Hirota Yukinori , Kornberg Thomas , Wechsler James A. , Barnoux C.
Published: May 2006

A series of double mutants carrying one of the thermosensitive mutations for DNA synthesis (
dnaA
, B, C, D, E, F, and G) and the
pol
A1 mutation of DeLucia and Cairns, were constructed. Enzyme activities of DNA Polymerases II and III were measured in each mutant. DNA Polymerase II activity was normal in all strains tested. DNA Polymerase III activity is thermosensitive specifically in those strains having thermoscnsitive mutations at the
dna
E locus. From these results we conclude that DNA Polymerases II and III are independent enzymes and that DNA Polymerase III is an enzyme required for DNA replication in
Escherichia coli
.
Defective Production of Mitochondrial Ribosomes in the
Poky
Mutant of
Neurospora crassa
Authors: Rifkin M. R. , Luck D. J. L.
Published: May 2006

A strain of
Neurospora crassa
containing a cytoplasmic mutation (
poky
) affecting mitochondrial function is shown to be deficient in small ribosomal subunits in the mitochondrion during the exponential growth phase. In the stationary growth phase, small subunits are more abundant and are present in mitochondrial ribosomal monomers. This change can be correlated with the return of mitochondrial cytochrome content to amounts approaching those of wild type mitochondria. The ribosomal defect shows an extrachromosomal pattern of inheritance in crosses of
poky
with wild type.
Interferon and Transcription of Early Virus-Specific RNA in Cells Infected with Simian Virus 40
Authors: Oxman Michael N. , Levin Myron J.
Published: May 2006

Treatment with interferon reduced the content of
early
virus-specific RNA, as well as the content of an
early
viral protein (T antigen), in monkey cells acutely infected with simian virus 40 (SV40). This unexpected finding suggests either that the action of interferon involves inhibition of the transcription of
early
SV40 messenger RNA, or that the SV40 genome contains a “proto-
early
” gene whose product is required for the transcription of the remaining
early
genes.
Promitochondria of Anaerobically Grown Yeast, V. Energy Transfer in the Absence of an Electron Transfer Chain
Authors: Groot G. S. P. , Kováč L. , Schatz G.
Published: May 2006

Promitochondria of anaerobically grown
Saccharomyces cerevisiae
lack cytochromes
aa
3
,
b, c
1
, and
c
, as well as ubiquinone, yet catalyze a P
i
-ATP exchange reaction that is sensitive to uncouplers, rutamycin, and atractyloside. The promitochondrial P
i
-ATP exchange reaction is abolished by the cytoplasmic “petite” mutation, as well as by growth of the cells in the presence of erythromycin, which indicates a role of mitochondrial protein synthesis in the assembly of the energy transfer system. These observations demonstrate that mitochondrial energy transfer can occur in the absence of a respiratory chain.
Separate Transport Systems for Sugars and Amino Acids in Developing Rat Kidney Cortex
Authors: Segal Stanton , Rea Claire , Smith Inez
Published: May 2006

The ability of renal cortical slices of newborn and young rats to accumulate a nonmetabolizable sugar, α-methylglucoside, is slight and does not reach adult capacity until 25 days of age. However, a rudimentary sugar transport system is present, as indicated by a further decrease in accumulation in the presence of phlorizin or absence of sodium ion.

Amino acid uptake in immature kidney tissue is not deficient; on the contrary, the tissue took up and concentrated more glycine and lysine than adult tissue. Decreased amino acid efflux from the immature cells appears to be the explanation. Concentration dependence of amino acid uptake was the same in 5-day-old and adult tissue.

These differences between the transport characteristics of a model sugar and representative amino acids during development indicate separate transport systems for the two types of substrate.
The Acyl Dihydroxyacetone Phosphate Pathway for Glycerolipid Biosynthesis in Mouse Liver and Ehrlich Ascites Tumor Cells
Authors: Agranoff Bernard W. , Hajra Amiya K.
Published: May 2006

The glycerol portion of lipids may be derived biosynthetically by reduction of dihydroxyacetone phosphate to glycerolphosphate, and then be acylated with fatty acids or, alternatively, dihydroxyacetone phosphate may first be acylated and then reduced to 1-acyl
sn
glcerol-3-phosphate. Since the former pathway utilizes NADH for reduction of the C-2 carbonyl, while the latter requires NADPH, we were able to compare the relative participation of the two pathways for phospholipid synthesis by measuring the incorporation of radioactivity from tritiumlabeled NADH and NADPH into C-2 of lipid glycerol. The acyl-dihydroxyacetone phosphate pathway plays a significant role in glycerolipid synthesis in mouse liver homogenates and a clearly dominant one in Ehrlich ascites tumor cell homogenates. This finding is related to a reported lack of glycerol-3-phosphate dehydrogenase in tumor cells and to their high glycerol ether lipid content.
Membrane-Associated Immunoglobulin of Rabbit Peripheral Blood Lymphocytes: Allelic Exclusion at the
b
Locus
Authors: Davie Joseph M. , Paul William E. , Mage Rose G. , Goldman Margaret B.
Published: May 2006

Light chain allotypic determinants were demonstrated on the surface of peripheral blood lymphocytes of rabbits. By means of a combined immunofluorescent and autoradiographic technique, a great majority of the individual lymphocytes of rabbits heteroxygous at the
b
locus were shown to have detectable quantities of only one allotype. A small proportion of lymphocytes appeared to possess both allelic forms of L chains.
NMR Studies on the Conformation of Derivatives of the Side Chain of Oxytocin: Examples of
cis-trans
Isomerism
Authors: Hruby Victor J. , Brewster A. I. , Glasel J. A.
Published: May 2006

The 220 MHz spectra reported in this paper show the existence of
cis-trans
isomerism about the Cys-Pro bond in (
S
-benzyl)-L-Cys-L-Pro-L-Leu-Gly(NH
2
) and about the Z-Pro bond in (
N
-benzyloxycarbonyl)-L-Pro-L-Leu-Gly(NH
2
). These peptides are derivatives of the side chain of oxytocin, which has the structure L-Pro-L-Leu-Gly(NH
2
). Taken in water-free (CD
3
)
2
SO, the spectra also show differences between the two isomers in the amide chemical shifts, which indicate interaction of the terminal end of the peptides with the rest of the residues. The ratio of the isomeric forms is about 2:3 for the
S
-benzylcysteinyl peptide, while it is 1:1 for the
N
-benzyloxycarbonyl-protected peptide. The probable assignment of peaks in isomers is discussed, in addition to routine spectral assignments based on extensive decoupling experiments.
Temperature-Sensitive Mutants of Bioluminescent Bacteria
Authors: Cline Thomas , Hastings J. W.
Published: May 2006

Mutants of a marine luminous bacterium, in which the ability to emit light is conditional upon temperature, have been isolated. The mutants obtained fall into three classes, which are readily distinguishable by both
in vivo
and
in vitro
criteria. In one class an altered, more temperature-sensitive luciferase is produced; in a second, the luciferase is actually not produced at the higher temperature. The third is defective in the production of an aldehyde-like factor that is a known requirement in the
in vitro
reaction.
Biochemical Studies on Adenovirus Multiplication, XIX. Resolution of Late Viral RNA Species in the Nucleus and Cytoplasm
Authors: Parsons J. Thomas , Gardner Jacqueline , Green Maurice
Published: May 2006

Late after infection of cultured human cells (KB) with adenovirus type 2, the nucleus contains heterogeneous viral RNA species ranging in size from 10 to 43 S. Four viral RNA species found in the nucleus (36, 38, 40, and 43 S) are synthesized predominantly during a 15-min labeling period with [
3
H]uridine, while smaller RNA species accumulate when labeling is continued for longer periods. In contrast, 6-8 viral RNA species, of sedimentation coefficient from 10 to 29 S, are found in the cytoplasm after a 30-min pulse label and a 2-hr chase. DNA-RNA hybridization-competition experiments demonstrate that viral RNA sequences present in nuclear 36-43S RNA are also present in cytoplasmic and polyribosomal RNA, suggesting that at least some of the cytoplasmic viral-specific RNA molecules are derived by cleavage of high molecular weight precursors from the nucleus.
Control of Translation by the Conformation of Messenger RNA
Authors: Fukami Hiroichi , Imahori Kazutomo
Published: May 2006

This study concerns the question of whether protein biosynthesis is controlled by the conformation of messenger RNA. When R17 bacteriophage RNA was first incubated in the presence of Mg
++
before being used as messenger in a cell-free system from
Escherichia coli
, significant changes in the incorporation of phenylalanine and histidine into protein were seen. The amounts of proteins synthesized were also altered. The changes were not due to degradation of R17 RNA nor to denaturation of a contaminating repressor; they could be reversed by appropriate treatment of the RNA. There forms of R17 RNA are therefore postulated for the control mechanism and characterized by their translational behavior. The significance of these forms with respect to their conformation is discussed.
The Mechanism of Protein Synthesis Activation After Fertilization of Sea Urchin Eggs
Authors: Metafora S. , Felicetti L. , Gambino R.
Published: May 2006

Upon fertilization of
Paracentrotus lividus
eggs, the ability of their ribosomes to form a ternary complex with poly(U) and phenylalanyl-tRNA is enhanced. In addition, it is possible to extract from ribosomes of the unfertilized egg a protein factor that inhibits polyphenylalanine synthesis by decreasing the binding of mRNA and aminoacyl-tRNA to the ribosomes. The observed increase in the rate of protein synthesis that occurs at fertilization could be accounted for by the removal of this inhibitory protein from the ribosomes.
Effects of L-Dopa on Norepinephrine Metabolism in the Brain
Authors: Chalmers J. P. , Baldessarini R. J. , Wurtman R. J.
Published: May 2006

Rats received intracisternal [
3
H]norepinephrine and, after 5 min, intraperitoneal L-dopa (100 mg/kg); they were killed at intervals during the subsequent 24 hr. Their brains were assayed for norepinephrine, L-dopa,
S
-adenosylmethionine, and [
3
H]norepinephrine and its metabolites. Rats that received L-dopa had markedly lower brain concentrations of
S
-adenosylmethionine and of
O
-methylated metabolites of [
3
H]norepinephrine than controls. An increase (15-40%) in brain norepinephrine content and accelerated turnover of brain norepinephrine was also observed in the animals receiving
L
-dopa. These changes were all transient, lasting about 1 hr and coinciding with the period when appreciable amounts of L-dopa were detectable in the brain.
Normal and Defective Repair of Damaged DNA in Human Cells: A Sensitive Assay Utilizing the Photolysis of Bromodeoxyuridine
Authors: Regan James D. , Setlow R. B. , Ley R. D.
Published: May 2006

A new technique has been developed for studying the extent of repair of UV-radiation damage to DNA in human cells. It is easy to use, has excellent sensitivity, and provides rapid quantitative estimates of repair. UV-irradiated cells whose DNA has been previously labeled with a radioisotope are grown after irradiation in non-radioactive bromodeoxyuridine, which is incorporated at the breaks induced by repair enzymes. After a period of growth in the thymidine analog the cells are exposed to a large flux of 313 nm radiation and then lysed on top of an alkaline sucrose gradient. Bromodeoxyuridine-containing sections of the DNA are thus selectively photolysed. Sedimentation in the alkaline gradient reveals the average molecular weight of disrupted segments and gives a measure of the number of breaks induced by repair enzymes over the whole period allowed for repair. The large change in average molecular weight observed upon exposure of normal repairing cells to 313 nm radiation is not observed in the repair-deficient cells from patients with xeroderma pigmentosum. The quantitative aspects of this assay for repair and its sensitivity should make it applicable to the study of repair induced by agents other than UV radiation.
RNA-Dependent RNA Polymerase Activity Associated with Virions and Subviral Particles of Myxoviruses
Authors: Chow Nang-Ly , Simpson Robert W.
Published: May 2006

In vitro
RNA synthesis is catalyzed by an enzyme found in purified virions of each of nine influenza strains tested. The extent of [
3
H]UTP incorporation observed is strain dependent, with an obligate requirement for Mn
2+
ions and RNA template. At least 30% of purified product RNA shows resistance to degradation by ribonuclease A and T1 before and after annealing with exogenous RNA from influenza virions.
Localization of Methylated Arginine in the A1 Protein from Myelin
Authors: Brostoff Steven , Eylar E. H.
Published: May 2006

Methylated arginine residues are found at only one site (position 107) of the polypeptide chain of the A1 protein, as shown by analysis of tryptic and peptic peptides; these analyses show 0.2 mole of N
G
-dimethylarginine and 0.4-0.8 mole of N
G
-monomethylarginine per mole of A1 protein. The methylated arginine residues appeared to be relatively resistant to tryptic attack. Both methylated derivatives were isolated from an enzymatic digest of the A1 protein; they were identified by chromatography, electrophoresis, and degradation to citrulline, methylamine, and ornithine on alkaline hydrolysis. The phylogenetic importance of the methylated derivatives was shown by their presence in the human, monkey, bovine, rabbit, guinea pig, rat, chicken, and turtle A1 proteins at the analogous position to that of the bovine sequence: [Formula: see text] We postulate that the methylated arginine residues may serve an important role in the myelin membrane
in situ
by stabilization of a double-chain structure for the A1 protein; such a double-chain conformation is induced by a (proline)
3
sequence located nearby.
Kinetics of Heterogeneous Chemical Reactions: A Theoretical Model for the Accumulation of Pesticides in Soil
Authors: Lin S. H. , Sahai R. , Eyring H.
Published: May 2006

A theoretical model for the accumulation of pesticides in soil has been proposed and discussed from the viewpoint of heterogeneous reaction kinetics with a basic aim to understand the complex nature of soil processes relating to the environmental pollution. In the bulk of soil, the pesticide disappears by diffusion and a chemical reaction; the rate processes considered on the surface of soil are diffusion, chemical reaction, vaporization, and regular pesticide application. The differential equations involved have been solved analytically by the Laplace-transform method.
Identification of 1,25-Dihydroxycholecalciferol, a Form of Vitamin D
3
Metabolically Active in the Intestine
Authors: Holick M. F. , Schnoes H. K. , DeLuca H. F.
Published: May 2006

A biologically active vitamin D
3
metabolite (“peak V metabolite”) more polar than 25-hydroxycholecalciferol has been isolated from chicken intestines in pure form as a mono(trimethylsilyl)ether derivative. The molecule has been identified as 1,25-dihydroxycholecalciferol by means of mass spectrometry, ultraviolet absorption spectrophotometry, and specific chemical reactions.
Pavlovian Pattern Learning by Nonlinear Neural Networks
Authors: Grossberg Stephen
Published: May 2006

This note describes laws for the anatomy, potentials, spiking rules, and transmitters of some networks of formal neurons that enable them to learn spatial patterns by Pavlovian conditioning. Applications to spacetime pattern learning and operant conditioning are then possible, if the conditioning is viewed as multi-channel Pavlovian conditioning in a highly inhomogeneous anatomy. In suitable anatomies, biases in learning because of axon collaterals with nonuniformly distributed diameters can be corrected if one properly couples the action potential to transmitter potentiation, and chooses signal velocity proportional to axon diameter. These anatomies can contain any number of cells. Anatomies exist in which patterns may be learned without their being practiced overtly, whereas persistent recall of old patterns without the learning of newly imposed patterns is impossible. Physiologically, this constraint has the trivial interpretation that signals from one cell to another first pass through the intervening synaptic knob. Mechanisms that control learning rates at times important to the network (e.g., reward and punishment times) can be discussed. Serial behavior like that described by Lashley is possible: this consists of sequential learning and performance of patterns faster than would be allowed by a motor-feedback control, at velocities influenced by arousal level, with the possibility of abrupt termination of performance if conflicting environmental demands arise. Analogs of pattern completion and mass action exist, as do phase transitions in memory (for some rate parameters and anatomies, memory is rigid, for others, it is plastic). The laws limit the ways in which these networks can be interconnected to yield specific discrimination, learning, memory, and recall capabilities.
High-Resolution X-Ray Diffraction Patterns of Crystalline Transfer RNA That Show Helical Regions
Authors: Kim Sung Hou , Quigley Gary , Suddath F. L. , Rich Alexander
Published: May 2006

Yeast phenylalanyl transfer RNA crystallizes in a simple orthorhombic unit cell (
a
= 33.2,
b
= 56.1,
c
= 161 Å), and the crystal yields an x-ray diffraction pattern with a resolution of 2.3 Å. From an analysis of the packing in the unit cell it is concluded that the molecular dimensions are approximately 80 by 33 by 28 Å. The diffraction pattern viewed along the
a
-axis has a distribution characteristic of double-helical nucleic acids. However, this distribution is not found when the pattern is viewed along the
b
-axis. This has been interpreted as indicating that the double-helical portions of the transfer RNA molecule are approximately half a helical turn in length, and therefore can contain 4-7 base pairs. These results are consistent with the cloverleaf formulation of transfer RNA secondary structure.
Sequences of Pituitary and Placental Lactogenic and Growth Hormones: Evolution from a Primordial Peptide by Gene Reduplication
Authors: Niall H. D. , Hogan M. L. , Sauer R. , Rosenblum I. Y. , Greenwood F. C.
Published: May 2006

Human placental lactogen has been found to resemble human pituitary growth hormone very closely in amino acid sequence, about 80% of the residues examined being identical in the two molecules when a revised sequence for growth hormone is used as the basis for comparison. The structural features responsible for the differing biological potency of the two hormones may therefore reside in rather limited regions of primary structure. The observation of internal sequence homologies within the pituitary growth hormone and prolactin and the placental lactogen molecules suggests that these polypeptide hormones may have evolved by genetic reduplication from a smaller common ancestral peptide. This finding directs further attention to subfragments of these molecules as possible possessors of intrinsic somatotrophic and lactogenic activity.
Enzymatic Characterization of a Mutant of
Escherichia coli
with an Altered DNA Ligase
Authors: Modrich Paul , Lehman I. R.
Published: May 2006

A temperature-sensitive, radiation-sensitive mutant of
Escherichia coli
has been assayed for DNA ligase activity
in vitro
. The strain contains a markedly reduced amount of DNA-joining activity, which is thermolabile. The formation of the ligase-adenylate intermediate is also temperature-sensitive
in vitro
. Two temperature-resistant revertants of the mutant contain normal amounts of a thermostable ligase. The mutant is killed by growth at 42°C, a temperature at which it displays aberrant DNA synthesis. These results suggest that the ligase is necessary for normal DNA metabolism and viability in this strain.
Partial Purification by Affinity Chromatography of Tyrosine Aminotransferase-Synthesizing Ribosomes from Hepatoma Tissue Culture Cells
Authors: Miller James V. , Cuatrecasas Pedro , Thompson E. Brad
Published: May 2006

This report describes a cell-free protein-synthesizing system derived from hepatoma tissue culture cells in which the synthesis of tyrosine aminotransferase is enhanced in relation to total protein synthesis. The enhancement was achieved by using affinity chromatography to select a specific fraction of ribosomes in which the proportion of tyrosine aminotransferase synthesis is higher than it is in unfractionated ribosomes.
Properties of Adenylate Cyclase of Lymphoid Cells
Authors: Makman Maynard H.
Published: May 2006

Adenylate cyclase of homogenates or lysates of mouse and rat lymphoid tissues was activated by the addition of fluoride ion, epinephrine, or norepinephrine, but not by any of several other hormones. The catecholamine stimulation was characterized as β-adrenergic. This activity was localized in the small lymphoid cells, was greater in thymic than in splenic or mesenteric node cells, and also was greater in mouse than in rat cells. Catecholamine-stimulated activity of mouse thymocytes remained constant from the 17-19th day of fetal development to 5 weeks after birth; it subsequently decreased to about one-half of the activity by 7-8 weeks. Similar decreases with age occurred in mouse spleen and rat thymus. In contrast, the glucagon-stimulated activity of rat liver increased during a similar period. Hypophysectomy of rats at 3 weeks did not influence the amount of cyclase activity of thymocytes assayed at 7 weeks.

When intact mouse thymocytes were first incubated in a culture medium at 37°C with epinephrine or norepinephrine, a second addition of catecholamine after cell lysis no longer stimulated the enzymes. This loss of stimulation was selective, since basal activity and stimulation by fluoride ion were not affected. Incubation of intact cells with phytohemagglutinin markedly decreased the activity of lysates, whether assayed in the presence or absence of catecholamine or fluoride. In contrast, phytohemagglutinin added directly to the assay had no effect. No alternations occurred in adenylate cyclase activity as a result of the incubation of a 1:1 mixture of thymocytes from two strains of mice selected for the capacity of the cells to produce a mixed lymphocyte response.
Properties of Squid Axon Membrane as Revealed by a Hydrophobic Probe, 2-
p
-Toluidinylnaphthalene-6-Sulfonate
Authors: Tasaki I. , Watanabe A. , Hallett M.
Published: May 2006

A hydrophobic probe, 2-
p
-toluidinylnaphthalene-6-sulfonate (TNS), was introduced into the interior of a squid giant axon and fluorescene properties of the TNS-stained axon were examined under illumination with polarized ultraviolet light. A transient reduction in fluorescence was observed when the axon was stimulated electrically. The light waves contributing to this fluorescence change were found to be nearly completely polarized, indicating that the probe molecules in the membrane are highly oriented. The emission spectra of these TNS-stained axons were examined at rest and during nerve excitation. The results obtained are considered to support the view that the process of nerve excitation is accompanied by a transition of the axon membrane from a hydrophobic to a hydrophilic state.
Purification and DNA-Binding Properties of the Catabolite Gene Activator Protein
Authors: Riggs A. D. , Reiness G. , Zubay G.
Published: May 2006

A protein required for the activation of the
lac
operon has been extensively purified and partly characterized. This protein, called CGA protein (catabolite gene activator protein, sometimes named CAP), is a dimer with subunits of 22,000 daltons. Purified CGA protein has a substantial affinity for DNA; this affinity is greatly strengthened by cAMP and strongly inhibited by cGMP. Other studies have shown that these cyclic nucleotides compete for a binding site on CGA protein. The opposing effects of the two cyclic compounds in DNA-CGA protein binding show a parallel behavior to their effects on the expression of the
lac
operon. Thus cAMP, in addition to CGA protein, is required for expression of the
lac
operon, whereas cGMP inhibits the expression. The obvious inference is that CGA protein activates the
lac
operon by binding to the DNA under the influence of cAMP. Thus, CGA protein seems to be a new type of regulatory protein: a DNA-binding activator.
New Forms of Bovine Carboxypeptidase B and Their Homologous Relationships to Carboxypeptidase A
Authors: Reeck Gerald R. , Walsh Kenneth A. , Hermodoson Mark A. , Neurath Hans
Published: May 2006

Two new forms of carboxypeptidase B have been isolated from spontaneously activated bovine pancreatic juice. The fully active enzymes contain an internal split at residues 92-93 and 95-96, respectively. Sequenator analysis of the amino terminal segments of the two chains of the enzyme has extended the sequence information by 51 amino acid residues. Comparison of 125 residues strengthens the hypothesis that carboxypeptidases A and B are homologous both in amino acid sequence and in three-dimensional conformation and implicates Asp-255 as the anionic site of substrate binding of the B enzyme.
Ring Orientation in βIonone and Retinals
Authors: Honig B. , Hudson B. , Sykes B. D. , Karplus M.
Published: May 2006

The ring orientation in β-ionone, all-
trans
retinal, and 11-
cis
retinal, relative to that of the polyene chain, has been determined by means of semi-empirical calculations and magnetic resonance measurements of the nuclear Overhauser effect and long-range coupling constants. The experimental results yield a distorted s-
cis
conformation about the C
6
-C
7
“single bond”, with the torsional angle in the range 30° to 70°. This agrees well with the semi-empirical potential function, which has a broad, rather flat minimum for angles from 40° to 120°. The temperature dependence of the NMR results provide confirmation for the form of the torsional potential.
Suggestive Evidence That the “Blocking Antibodies” of Tumor-Bearing Individuals May Be Antigen-Antibody Complexes
Authors: Sjögren H. O. , Hellström I. , Bansal S. C. , Hellström K. E.
Published: May 2006

Sera from mice carrying progressively growing sarcomas induced by Moloney virus or methylcholanthrene can block the cytotoxic effect of lymphocytes immune to the tumor-specific antigens of the respective neoplasms. The blocking effect can be specifically removed by absorbing sera with the respective types of tumor cells, and it can be recovered from these cells by elution at low pH. If the low pH is maintained, it is possible to separate out a low and a high molecular weight fraction from the eluates. If the fractions are added to the target cells for 45 minutes and then removed, neither of these fractions can block lymphocyte-mediated cytotoxicity, while a 1:1 mixture of them has a specific blocking effect. If they are admixed with the lymphocytes, incubated for 1 hr, and then allowed to incubate with the target cells and lymphocytes during the entire 2 days of the test, the low molecular weight fraction, as well as the mixture, but not the high molecular weight fraction, has a blocking activity.

It is suggested that the blocking factor in sera from tumor-bearing animals, as regularly tested, is an antigen-antibody complex, capable of binding to the target cells and/or reacting with lymphocytes immune to their antigens, thus blocking the lymphocytes' reactivity; the latter reaction is postulated to be of a temporary nature.
A Translocation-Associated Ribosomal Conformation Change Detected by Hydrogen Exchange and Sedimentation Velocity
Authors: Chuang De-Maw , Simpson Melvin V.
Published: May 2006

Translocation in ribosomes consists of transposition of peptidyl-tRNA from the aminoacyl to the peptidyl site and, probably concomitantly, the movement of ribosomes on mRNA. Does a conformational change in the ribosome provide the motive force for this process? Hydrogen exchange and sedimentation velocity experiments indicate that the
Escherichia coli
ribosome does undergo a conformational change associated with translocation. When pretranslocational ribosomes carrying acetyldiphenylalanyl-tRNA in the aminoacyl site were incubated with G factor and GTP, translocation occurred, with a concomitant increase in hydrogen exchange rate and a decrease in sedimentation constant. These changes did not occur when GTP was replaced by a nonhydrolyzable analogue, GDP-CH
2
-P, and they were blocked by the antibiotics fusidic acid and thiostrepton. When posttranslocational ribosomes were cycled back to the pretranslocational state by T factor, GTP, and phenylalanyl-tRNA, the sedimentation constant reverted to the original value. Whether or not this conformation change drives translocation requires further study.
Microbial Metabolism of the Isoprenoid Alkane Pristane
Authors: McKenna E. J. , Kallio R. E.
Published: May 2006

The “inert” hydrocarbon pristane (2,6,10,14-tetramethylpentadecane) can be utilized as the sole source of carbon and energy for growth of a coryneform soil isolate. Identification of the metabolites 4,8,12-trimethyltridecanoic acid and α-methylglutaric acid indicates that two pathways of fatty acid metabolism operate in this bacterial strain.

The widespread use of pristane as a biological marker appears to be predicated on its structural similarity to phytol and its apparent stability, which may be only a reflection of the inability of microorganisms to carry out its anaerobic destruction.
Composition of Basal and Stimulated Hepatic Bile in Baboons, and the Formation of Cholesterol Gallstones
Authors: McSherry Charles K. , Glenn Frank , Javitt Norman B.
Published: May 2006

The baboon,
Papio
, has been found to be a model for the study of the pathogenesis of cholesterol cholelithiasis in man. Studies of the physiologic variations in hepatic bile composition indicate a cyclic pattern to the proportions of cholesterol, lecithin, and bile salt in hepatic bile. During reabsorption of the bile salt pool from the intestines (stimulated flow), hepatic bile is characteristically undersaturated with cholesterol. After reabsorption of the bile salt pool (basal flow), hepatic bile is characteristically supersaturated with cholesterol. This typical pattern of basal and stimulated hepatic bile occurs irrespective of the presence of cholesterol stones in the baboon. Recognition of these two types of hepatic bile and their interrelationship during admixture in the gallbladder provides new insight into the pathogenesis of gallstone formation.
Immunological Evidence for an Inactive Precursor of Collagen Proline Hydroxylase in Cultured Fibroblasts
Authors: McGee James O'D. , Langness Uwe , Udenfriend Sidney
Published: May 2006

A specific antibody to rat collagen proline hydroxylase has been used to measure the amount of “enzyme” protein in cultured mouse fibroblasts (L-929 cells) during normal growth, and under other conditions that cause an increase in enzyme activity. Collagen proline hydroxylase activity per mg of cell protein increased 24-fold as the cells progressed through the logarithmic to the stationary phase of growth, while the cellular concentration of immunologically reactive protein changed only slightly. Similar results were obtained with cells in early log phase in which enzyme activity was stimulated severalfold by cell concentration or lactate treatment without a corresponding change in cellular antigen. It has also been shown that the enzymatically inactive antigen in these fibroblasts competes effectively for antibody-binding sites with partially purified enzyme. It is concluded that early-log-phase fibroblasts contain an inactive form of collagen proline hydroxylase which may be a precursor of the functional enzyme.
Antitumor Activity and Toxicity of Salts of Inorganic Group IIIa Metals: Aluminum, Gallium, Indium, and Thallium
Authors: Hart Michael M. , Adamson Richard H.
Published: May 2006

The toxicity and antitumor activity of salts of the Group IIIa metals aluminum, gallium, indium, and thallium were determined. With the (lethal dose)
50
as a measure, the decreasing order of toxicity was TlCl
3
≥ In(NO
3
)
3
> Ga(NO
3
)
3
> Al(NO
3
)
3
. All four metals exhibited antitumor activity, but when the tumor was inoculated by a route different from that of the drug, only Ga
+3
and, to a lesser extent, In
+3
inhibited tumor growth. Ga(NO
3
)
3
was found to inhibit the growth of three out of four rodent solid tumors. Gallium therefore has potential therapeutic usefulness for treatment of solid tumors in man.
Role of Exonuclease and β Protein of Phage λ in Genetic Recombination, V. Recombination of λ DNA
in Vitro
Authors: Cassuto Era , Lash Terry , Sriprakash K. S. , Radding Charles M.
Published: May 2006

The sequential action of λ exonuclease and polynucleotide ligase upon redundant joint molecules is sufficient to produce intact polynucleotide chains and heat-stable, biologically active molecules of λ DNA, whereas the action of ligase alone is insufficient. These results (
a
) confirm the previously described mechanism of single-strand assimilation, including a subsidiary mechanism by which the further action of λ exonuclease is arrested when a redundant strand is completely assimilated, and (
b
) represent a simulation of the steps in genetic recombination that follow the formation of biparental complexes (synapsis). λ exonuclease is postulated to catalyze a concerted reaction that includes exposure of complementary sequences, formation of heteroduplex regions, and elimination of redundant branches.
Entropic Contributions to Rate Accelerations in Enzymic and Intramolecular Reactions and the Chelate Effect
Authors: Page Michael I. , Jencks William P.
Published: May 2006

It is pointed out that translational and (overall) rotational motions provide the important entropic driving force for enzymic and intramolecular rate accelerations and the chelate effect; internal rotations and unusually severe orientational requirements are generally of secondary importance. The loss of translational and (overall) rotational entropy for 2 → 1 reactions in solution is ordinarily on the order of 45 entropy units (e.u.) (standard state 1 M, 25°C); the translational entropy is much larger than 8 e.u. (corresponding to 55 M). Low-frequency motions in products and transition states, about 17 e.u. for cyclopentadiene dimerization, partially compensate for this loss, but “effective concentrations” on the order of 10
8
M may be accounted for without the introduction of new chemical concepts or terms.
On the Control of the Induction of β-Galactosidase in Synchronous Cultures of
Escherichia coli
Authors: Goldberg Richard B. , Chargaff Erwin
Published: May 2006

The mode of induction of β-galactosidase (EC 3.2.1.23) in synchronously growing cultures of two Hfr strains of
Escherichia coli
K12 was investigated. Cells can be induced to form the enzyme during any portion of the cell cycle; but when they are grown permanently in the presence of an inducer, enzyme synthesis is discontinuous. The interruption of β-galactosidase synthesis appears to be geared to the growth cycle: it occurs when the cells are dividing actively. The observation that
lac
-specific messenger RNA is produced also in the absence of detectable enzyme synthesis suggests the existence of a control mechanism operating on the level of translation.
Effect of Leukocyte Transfusion in a Child with Type II Mucopolysaccharidosis
Authors: Knudson Alfred G. , Ferrante Nicola Di , Curtis John E.
Published: May 2006

Treatment of a child affected by type II mucopolysaccharidosis (Hunter's syndrome) with leukocyte transfusions produced dramatic biochemical and clinical changes. The biochemical changes, consisting of greatly increased urinary excretion of glycosaminoglycans and their products of degradation, were transient. The clinical changes, on the other hand, were protracted, which suggests that the mobilization and degradation of stored glycosaminoglycans was not followed by their reaccumulation to initial levels. The effects obtained with this treatment are superior to those produced by plasma infusion, and have implications for therapeutic attempts in the treatment of other hereditary diseases.
Translocation of Messenger RNA and “Accommodation” of fMet-tRNA
Authors: Thach Sigrid S. , Thach Robert E.
Published: May 2006

Messenger RNA is moved a distance of approximately three nucleotides in the 5′ direction relative to the ribosome during the translocation of peptidyl-tRNA from the A to the P site. This movement is catalyzed by G factor and is dependent on the hydrolysis of GTP. In contrast, mRNA is not moved during the f
2
-catalyzed hydrolysis of GTP that is involved in the activation of ribosome-bound fMet-tRNA. This second type of GTP-dependent reaction has been named “Accommodation”.
Inhibition by Siomycin and Thiostrepton of Both Aminoacyl-tRNA and Factor G Binding to Ribosomes
Authors: Ll Juan Modole , Cabrer Bartolomé , Parmeggiani Andrea , Azquez David V
Published: May 2006

Siomycin, a peptide antibiotic that interacts with the 50S ribosomal subunit and inhibits binding of factor G, is shown also to inhibit binding of aminoacyl-tRNA; however, it does not impair binding of fMet-tRNA and completion of the initiation complex. Moreover, unlike other inhibitors of aminoacyl-tRNA binding (tetracycline, sparsomycin, and streptogramin A), siomycin completely abolishes the GTPase activity associated with the binding of aminoacyl-tRNA catalyzed by factor T
u
. A single-site interaction of siomycin appears to be responsible for its effect on both the binding of the aminoacyl-tRNA-T
u
-GTP complex and that of factor G.
Photo-Affinity Labels for Adenosine 3′:5′-Cyclic Monophosphate
Authors: Brunswick D. J. , Cooperman Barry S.
Published: May 2006

Three derivatives of cyclic AMP that are potentially useful as photo-affinity labels were synthesized. One of these derivatives is, upon photolysis, specifically incorporated into the cyclic AMP-binding site of rabbit muscle phosphofructokinase. The use of these derivatives in isolating and identifying cyclic AMP receptor sites is discussed.
Mechanism of Initiation of Repression of
In Vitro
Transcription of the
Lac
Operon of
Escherichia coli
Authors: Eron Larry , Block Ricardo
Published: May 2006

A cyclic AMP-binding protein (CAP protein), cyclic AMP, and RNA polymerase holoenzyme are shown to initiate
lac
transcription at the
lac
promoter.
Lac
repressor appears to control transcription by preventing RNA polymerase and/or CAP protein from binding to the
lac
promoter. Results support the idea that the
lac
promoter is composed of two sites that interact with CAP protein and RNA polymerase holoenzyme. The promoter can be altered by mutation so that holoenzyme alone can initiate
lac
transcription correctly.
Regulation of Protein Synthesis Initiation in HeLa Cells Deprived of Single Essential Amino Acids
Authors: Vaughan Maurice H. , Pawlowski Philip J. , Forchhammer J.
Published: May 2006

In HeLa cells deprived of valine, histidine, or methionine initiation of protein synthesis decreases rapidly and disaggregation of polyribosomes also occurs. The mechanism of inhibition does not seem to involve the supply of RNA in the cell, and thus it differs from the initiation of inhibition at elevated temperatures. Polyribosomes rapidly form again if the missing amino acid is restored, even in the presence of actinomycin D.
Pantetheine-Linked Peptide Intermediates in Gramicidin S and Tyrocidine Biosynthesis
Authors: Kleinkauf Horst , Roskoski Robert , Lipmann Fritz
Published: May 2006

To study the function of pantetheine in gramicidin S and tyrocidine biosynthesis, pepsin digests of the polymerizing enzymes, of which only the heavy ones contain pantetheine, were analyzed. The digests of gramicidin S enzymes charged with either [
14
C]proline or with D-phenylalanyl-[
14
C]proline, were analyzed by thin-layer chromatography; only the dipeptide showed a derivative associated with pantetheine. Similar results were obtained from the heavy tyrocidine enzyme charged with either [
14
C]asparagine alone or with the pentapeptide D-Phe-Pro-Phe-D-Phe-[
14
C]Asn. Several radioactive products appeared on the thin-layer chromatograms of both these digests; association with pantetheine was found only in the case of the pentapeptide. Exposure of the chromatogram from the pentapeptide-labeled digest to performic acid and development in a second direction separated the peptide from pantetheine, indicating that a nascent peptide was originally linked to the cofactor by a thioester bond. The connection of pantetheine only with peptide residues appears to confirm its role in transpeptidation during peptide chain growth.
Cortisone Stimulation of Nucleolar RNA Polymerase Activity
Authors: Yu Fu-Li , Feigelson Philip
Published: May 2006

Four hours after intraperitoneal injection of cortisone acetate into rats, hepatic nuclei had an enhanced ability to incorporate labeled nucleoside triphosphates into RNA
in vitro
. When the nuclei were further fractionated into nucleolar and extranucleolar (nucleoplasmic) fractions, it was found that this hormonal effect was localized exclusively in the nucleolar fraction. This increased transcriptive activity potentially could be due to either (
a
) an increased availability of the DNA template or (
b
) an increase in the amount or catalytic efficiency of the RNA polymerase, or both. In order to distinguish between these possibilities, actinomycin D was used to inhibit the template function of endogenous nucleolar DNA and a synthetic template, polydeoxycytidylate, which is insensitive to actinomycin D and codes for polyriboguanylate synthesis, was used to evaluate RNA polymerase activity. These studies indicate that the increased RNA synthesis evident in nucleoli isolated from livers of rats four hours after cortisone treatment is largely a consequence of elevated levels of RNA polymerase.
Nucleic Acid Polymerases of the Developing Chicken Embryo: A DNA Polymerase Preferring a Hybrid Template
Authors: Stavrianopoulos Jannis G. , Karkas John D. , Chargaff Erwin
Published: May 2006

This paper presents a preliminary survey of the nucleic acid polymerases of the developing chicken embryo, especially of the 4-day stage. The predominant activity is that of a DNA polymerase preferring a DNA-RNA hybrid as the template. The enzyme, which is activated by Mn
2+
ions and inhibited by
p
-chloromercuriphenylsulfonate, copies preferentially the ribo strand of a hybrid, such as poly(rA)·poly(dT), but is relatively inactive with all-ribo duplexes. DNA polymerase I of
Escherichia coli
was also found to use the hybrid template with high efficiency, copying preferentially the ribo strand. With the chicken enzyme, the template activity of denatured DNA was increased tenfold by simultaneous transcription with RNA polymerase. DNA polymerase activity reaches a maximum in the 6- to 8-day chicken embryo and then declines progressively to about one-third of the maximal value in the adult chicken.
Genetic Analysis of Cell Heredity in Imaginal Discs of
Drosophila melanogaster
Authors: Garcia-Bellido A. , Merriam J. R.
Published: May 2006

Somatic crossing-over was used in heterozygous
Drosophila melanogaster
to effect clonal homozygosity for three mutants (
h, Hw, ac
). In these mutants, one type of process, chaetae, replaces another type, trichomes, in specific patterns on the adult fly. Heterozygous individuals were irradiated at different larval or pupal ages with x-rays and the somatic crossing-over was identified in the adult cuticle by genetically coupled mutants serving as cell markers of chaetae and trichomes. Induction of homozygosis more than 8 hr before puparium formation resulted in autonomous differentiation of the mutant pattern in the homozygous patch of tissue for the three mutants tested; homozygosis induced within 8 hr of puparium formation was not followed by expression of the corresponding genotype. 8 hr before puparium formation, each cell type still has to divide twice before metamorphosis and differentiation. Thus, the genetically conditioned decision of a specific cell to differentiate either a chaeta or a trichome is made during the growth of the wing imaginal disc and is transmitted clonally to descendant cells. Once this decision has been made, subsequent changes in the genotype of the cell or of its daughters are not material to the fate of the cell. We introduce the term “perdurance” to designate the persistence of a cellular developmental fate for several cell generations after the loss of the genetic basis for that cellular development.
A Novel Closed-Circular Mitochondrial DNA with Properties of a Replicating Intermediate
Authors: Kasamatsu Harumi , Robberson Donald L. , Vinograd Jerome
Published: May 2006

A fraction of the covalently closed mitochondrial DNA in mouse L cells contains a replicated heavy-strand segment that is hydrogen bonded to the circular light strand. The inserted single strand is dissociable from the circular duplex at an elevated temperature.