bluuebunny/crossref_metadata_2025 huggingface dataset:
Transcription of the Polyoma Virus Genome: Synthesis and Cleavage of Giant Late Polyoma-Specific RNA
Authors: Acheson Nicholas H. , Buetti Elena , Scherrer Klaus , Weil Roger
Published: May 2006

The size of virus-specific RNA synthesized in cultured mouse kidney cells infected with polyoma virus was estimated by electrophoresis and sedimentation analysis of RNA extracts from whole cells. Newly synthesized “late” polyoma-specific RNA appears as “giant” molecules of heterogeneous size, up to several times larger than a strand of polyoma DNA (1.5 × 10
6
daltons). Treatment with dimethylsulfoxide or urea showed that the large size of these molecules is not due to aggregation. Giant polyoma-specific RNA is strikingly similar in size distribution to “nuclear messenger-like” RNA (“heterogeneous nuclear” RNA) of the host cell. Subsequent to its synthesis, some of the giant polyoma-specific RNA appears to be cleaved to at least three smaller species.
Purification and
In Vitro
Transcription of a Transfer RNA Gene
Authors: Daniel Violet , Beckmann Jacques S. , Sarid Sara , Grimberg Jacob I. , Herzberg Max , Littauer Uriel Z.
Published: May 2006

A gene specifying tyrosine transfer RNA has been purified and transcribed
in vitro
. The purification procedure made use of two specialized transducing phages carrying the tRNA
Tyr
gene of
Escherichia coli
inserted into their DNA in opposite orientations. The separated heavy strands of the two phages were annealed and the single-stranded tails of the resulting hybrid were removed by digestion with
Neurospora
endonuclease. The size of the purified double-stranded structures was determined by electron microscopy. These isolated duplexes served as template for the
in vitro
transcription of tRNA
Tyr
-like molecules.
The Antibody Response of Mice to Murine Leukemia Virus in Spontaneous Infection: Absence of Classical Immunologic Tolerance
Authors: Oldstone Michael B. A. , Aoki Tadao , Dixon Frank J.
Published: May 2006

Gross murine leukemia virus is the etiologic agent of spontaneous leukemias of AKR mice. Despite the persistence of the Gross virus throughout their life, these mice are not immunologically tolerant to the virus. Specific antibodies to Gross antigens can be detected in the kidney where they have been deposited in the glomeruli, apparently in the form of Gross antigen-antibody complexes.
Noncooperativity of the αβ Dimer in the Reaction of Hemoglobin with Oxygen
Authors: Hewitt J. A. , Kilmartin J. V. , Eyck L. F. Ten , Perutz M. F.
Published: May 2006

The theory that the αβ dimer is the functional unit of cooperativity in hemoglobin has been tested by determination of the oxygen equilibrium curve of stable deoxy dimers, obtained by the addition of 0.9 M MgCl
2
to human des-Arg 141α-hemoglobin. Cooperativity was absent in this medium, but was regained on transfer of the hemoglobin to a dilute phosphate buffer, where tetramers reformed. X-ray analysis of crystals of oxy- and deoxy-des-Arg hemoglobins showed that the removal of Arg 141α would leave the structure of αβ dimers unchanged. Nonreactivity of the sulfhydryl groups at 112β proved that the subunits in deoxy dimers form the same contact as in oxy dimers, namely α
1
β
1
, and that no significant dissociation into free subunits occurs in 0.9 M MgCl
2
. The absorption spectrum of the deoxy dimers corresponded to the sum of the spectra of the free deoxy α and β subunits, and was different from that of the deoxy tetramer, showing the constraining salt bridges formed by the C-terminal residues in the tetramer to be necessary for the spectral changes normally observed on association of the deoxy subunits.
In Vitro
Synthesis of DNA Complementary to Purified Rabbit Globin mRNA
Authors: Ross Jeffrey , Aviv Haim , Scolnick Edward , Leder Philip
Published: May 2006

Several properties of the viral RNA-dependent DNA polymerases and of rabbit globin mRNA make it possible to consider synthesis of the globin gene
in vitro
. These enzymes copy an RNA template using a short sequence of complementary nucleotides as a primer. Furthermore, globin mRNA has a 3′-terminal sequence of adenylic acid residues that make it particularly suitable as a template, since oligo(dT) can be annealed to a specific site on the mRNA. This small primer could phase the DNA polymerase, possibly ensuring that replication is initiated from that end of the globin message. We have used this approach and find that purified mRNA is an efficient template for the polymerase enzyme. The reaction requires the RNA template and the four deoxyribonucleoside triphosphates, and it is markedly stimulated by the addition of oligo(dT). Consistent with the expectation that the oligo(dT) uniquely phases the polymerase at an adenine-rich region in the globin message, oligo(dG), oligo(dC), and oligo(dA) fail to serve as primers. The product has a density intermediate between that of DNA and RNA, and shifts to a lighter DNA density after treatment with base. Further, it is specifically complementary to globin mRNA and sediments slightly faster in an alkaline sucrose gradient than a DNA standard that has a molecular weight of 129,000. The data suggest that a major portion of the DNA product is a sequence of at least 500 bases, about 50 more than would be necessary to encode rabbit globin. The potential usefulness of this interesting product is discussed.
Light Chain Sequences of Human IgM Cold Agglutinins
Authors: Capra J. Donald , Kehoe J. Michael , Williams Ralph C. , Feizi Ten , Kunkel Henry G.
Published: May 2006

The amino-terminal amino-acid sequence has been determined for the kappa light chains of nine IgM cold agglutinins with specificity for blood group-related carbohydrate antigens. Six of the nine sequences corresponded to the prototype VK
III
subgroup pattern, two to that of subgroup VK
II
, and only one to the VK
I
subgroup. This distribution of kappa subgroups differs markedly from that of normal and myeloma proteins sequenced to date, where the VK
I
subgroup is more prevalent than either VK
II
or VK
III
. Evidence is presented that supports the conclusion that the unusual subgroup distribution relates to the antibody property itself and not to some other attribute of these molecules.
Ultrastructure of the Human Complement Component, Clq
Authors: Shelton Emma , Yonemasu Kunio , Stroud Robert M.
Published: May 2006

The human complement component, Clq, is a fragile molecule of delicate structure consisting of three distinct parts, a central subunit, connecting strands, and terminal subunits. Each terminal subunit is further subdivided into a large and a small subunit, and the central subunit appears to be divided into two equal parts. In the intact molecule, six connecting strands link six terminal subunits by their larger subdivision to the central subunit. The overall diameter of the molecule when viewed from the “top” is about 35 nm (350 Å).
A Partial Sequence of Nuclear Events in Regenerating Rat Liver
Authors: Mayfield John E. , Bonner James
Published: May 2006

When two lobes of the liver of the adult rat are removed, the cells of the remaining lobe are aroused to renewed cell division. We have studied the early events in such regeneration. The first observable response to such partial hepatectomy is the production in the liver nuclei of rapidly-labeled high-molecular-weight RNA of sequences not produced by normal liver. This is followed, with a lag of about 1 hr, by the appearance of increased (above normal) amounts of chromosomal RNA, again of sequences not produced by normal liver. With a lag of another hour, the template activity in support of RNA synthesis of the liver chromatin increases substantially. These events occur before initiation of DNA synthesis in the cells of the regenerating liver.
Initiation Factor 2-Dependent Ribosomal Binding of
N
-Formylmethionyl-Transfer RNA Without Added Guanosine Triphosphate
Authors: Mazumder Rajarshi
Published: May 2006

Evidence is presented that suggests that GTP (or 5′-guanylylmethylene diphosphonate) is not essential for either formation of an AUG-directed, initiation factor IF-2-dependent initiation complex on the 30S subunit or for positioning of fMet-tRNA on the peptidyl site. However, recycling of limiting amounts of IF-2 requires both GTP and the 50S subunit. The formation of the complex IF-2-30S as an intermediate in polypeptidechain initiation is suggested.
Transcription in Yeast: A Factor that Stimulates Yeast RNA Polymerases
Authors: Mauro Ernesto Di , Hollenberg Cornelis P. , Hall Benjamin D.
Published: May 2006

Yeast cells contain an RNA polymerase factor, π, which is a heat-stable protein with an apparent molecular weight of 12,000. This factor stimulates transcription of calf-thymus, salmon-sperm, yeast-nuclear, and T4-phage DNA. It stimulates transcription by each of the four yeast-nuclear RNA polymerases, by rat-liver RNA polymerases I and II, and by
Escherichia coli
RNA polymerase. π-Factor can cause each of the eukaryotic RNA polymerases to become insensitive to rifamycin AF-013, but does not stop inhibition of
E. coli
RNA polymerase by rifamycin AF-013. Stimulation of transcription by π-factor is general, and does not apply only to a limited class of genes. Apparently, π-factor stimulates transcription by increasing the proportion of RNA polymerase binding events that leads to the initiation of RNA chains.
The Rapid Turnover of RNA Polymerase of Rat Liver Nucleolus, and of Its Messenger RNA
Authors: Yu Fu-Li , Feigelson Philip
Published: May 2006

Turnover rates of the components of systems for RNA synthesis of rat-liver nucleus, nucleolus, and nucleoplasm were investigated. Cycloheximide administered
in vivo
selectively diminished nucleolar RNA synthesis
in vitro
. In contrast to the relatively stable nucleoplasmic RNA polymerase, nucleolar RNA polymerase (polymerase I) from rat liver decays rapidly upon cycloheximide administration, following pseudo-first order kinetics with a half-life of about 1.3 hr. Cycloheximide elicits this effect not through direct interaction with nucleolar RNA polymerase itself, nor by alteration of template function, but rather by inhibition of
de novo
synthesis of one or more of the protein components of nucleolar RNA polymerase. Similarly, when actinomycin-D was administered
in vivo
to inhibit RNA synthesis, the rate of decay of nucleolar RNA polymerase, assayed in the presence of exogenous poly d(A-T) template, was similar to that observed after cycloheximide administration. Thus, the messenger RNA(s) that codes for one or more of the catalytically essential polypeptide components of this enzyme turn over very rapidly with a half-life considerably shorter than 1.3 hr. The rapidity of turnover of both the enzyme protein and its messenger RNA(s) renders nucleolar RNA polymerase highly responsive to altered transcriptional, translational, or post-translational modulation. The marked differences in turnover rates of nucleolar and nucleoplasmic RNA polymerases indicate that at least certain of the protomeric components of nucleolar RNA polymerase I are distinct from those of nucleoplasmic RNA polymerases II and III.
Endonucleolytic Activity from
Micrococcus luteus
That Acts on γ-Ray-Induced Damage in Plasmid DNA of
Escherichia coli
Minicells
Authors: Paterson M. C. , Setlow R. B.
Published: May 2006

A partially purified extract from
Micrococcus luteus
contains endonucleolytic activity toward ultraviolet (UV)-irradiated deoxyribonucleic acid (DNA). We found that the same extract also acts on superhelical, covalently-closed circular λ
dv
DNA isolated from γ-irradiated minicells of
E. coli
. The introduction of nicks in isolated covalently-closed circular DNA by an endonuclease in the extract results in relaxed circles, and these two circular DNA species are easily distinguishable by their sedimentation properties in alkaline sucrose. The frequency with which the endonuclease-susceptible lesions are produced in superhelical DNA is only marginally enhanced when
60
Co γ-rays are administered to an aerobic rather than an anoxic minicell suspension. The ratio of endonuclease-sensitive defects to single-strand scissions, induced by γ-irradiation in air, is about 1:3. The nuclease-sensitive lesions disappear from γ-irradiated minicells during incubation after radiation presumably as a consequence of excision repair. Since the addition of UV-irradiated calf-thymus DNA depresses the ability of the
M. luteus
extract to attack not only UV-damaged
E. coli
DNA (a known substrate for the so-called UV-specific endonuclease that catalyzes the initial single-strand incision adjacent to the structural defect) but, also λ
dv
DNA injured by γ-rays, we conclude that physicochemical alterations induced by both types of radiation are recognized by one and the same endonuclease.
Configuration of the C(20) Epimer of 7,8-Dihydrobatrachotoxinin A
Authors: Karle Isabella L.
Published: May 2006

7,8-Dihydrobatrachotoxinin A is an intermediate in the synthesis of batrachotoxin, the extremely potent venom from the Colombian frog
Phyllobates aurotaenia
. A crystal structure analysis by x-ray diffraction has confirmed that the intermediate is identical with the natural batrachotoxinin A except for the saturation of the C(7)-C(8) bond. There are seven asymmetric carbon atoms in the molecule. The
cis
A/B and C/D ring junctions cause the molecule to assume the characteristic shape of cardioactive steroids. A cage is formed from the A-ring, atom C(9), and the O atom that makes the ether linkage between C(3) and C(9).
Computation of Large Molecules with the Hartree-Fock Model
Authors: Clementi Enrico
Published: May 2006

The usual way to compute Hartree-Fock type functions for molecules is by an expansion of the one-electron functions (molecular orbitals) in a linear combination of analytical functions (LCAO-MO-SCF, linear combination of atomic orbitals—Molecular Orbital—Self Consistent field). The expansion coefficients are obtained variationally. This technique requires the computation of several multicenter two-electron integrals (representing the electron-electron interaction) proportional to the fourth power of the basis set size. There are several types of basis sets; the Gaussian type introduced by S. F. Boys is used herein. Since it requires from a
minimum
of 10 (or 15) Gaussian-type functions to about 25 (or 30) Gaussian functions to describe a second-row atom in a molecule, the fourth power dependency of the basis set has been the
de facto bottleneck of quantum chemical computations in the last decade
.

In this paper, the concept is introduced of a “dynamical” basis set, which allows for drastic computational simplifications
while retaining full numerical accuracy
. Examples are given that show that computational saving in computer time of more than a factor of one hundred is achieved and that large basis sets (up to the order of several hundred Gaussian functions per molecule) can be used routinely.

It is noted that the limitation in the Hartree-Fock energy (correlation energy error) can be easily computed by use of a statistical model introduced by Wigner for solid-state systems in 1934.

Thus,
large molecules
can now be simulated by computational techniques without reverting to semi-empirical parameterization and without requiring enormous computational time and storage.
Alteration of the Cytotoxic Action of Sensitized Lymphocytes by Cholinergic Agents and Activators of Adenylate Cyclase
Authors: Strom Terry B. , Deisseroth Albert , Morganroth Joel , Carpenter Charles B. , Merrill John P.
Published: May 2006

The cytotoxic action of lymphocytes upon cells bearing alloantigens to which they are sensitized is inhibited by agents that elevate intracellular amounts of 3′:5′-cyclic AMP: prostaglandin E
1
, cholera toxin, and theophylline. Cholinergic agents, added in the range of 1 to 100 pM, enhance cytotoxicity, an effect that is blocked by atropine. Because cholinergic agents elevate cyclic GMP in other
in vitro
systems, these findings suggest that the cytotoxic process effected by sensitized lymphocytes is a secretory phenomenon modulated by cyclic AMP and cyclic GMP.
Guanosine 3′:5′-Cyclic Monophosphate: A Possible Intracellular Mediator of Mitogenic Influences in Lymphocytes
Authors: Hadden John W. , Hadden Elba M. , Haddox Mari K. , Goldberg Nelson D.
Published: May 2006

Adenosine 3′:5′-cyclic monophosphate (cyclic AMP) has been shown to have an antimitotic role in various cell types, and it has been hypothesized that a decrease of cyclic AMP concentration in the cell initiates or permits cell division. This hypothesis has been evaluated with respect to clonal proliferation of lymphocytes. Two potent mitogenic agents, phytohemagglutinin and concanavalin A, which induce thymic-dependent lymphocytes to undergo clonal proliferation, were examined for their ability to initiate proliferation and to alter the concentrations of cyclic AMP and guanosine 3′:5′-cyclic monophosphate (cyclic GMP) in purified human peripheral blood-lymphocytes. Optimal mitogenic concentrations of phytohemagglutinin and concanavalin A produced 10- to 50-fold increases in the concentration of lymphocyte cyclic GMP within the first 20 min of exposure to the mitogens. No changes were seen in the concentration of cyclic AMP after stimulation with either mitogen in purified form. Increases of less than 2-fold in the concentration of lymphocyte cyclic AMP observed with a less purified preparation of phytohemagglutinin could be attributed to the agglutinating rather than the mitogenic properties of the mitogen. A revised hypothesis is presented in which a temporally discrete rise in lymphocyte cyclic GMP concentration is viewed as an active signal to induce proliferation, while the elevation of cyclic AMP concentration in these cells is viewed as a regulatory influence that limits or inhibits mitogenic action.
Evidence for Coadaptation in
Avena barbata
Authors: Allard R. W. , Babbel G. R. , Clegg M. T. , Kahler A. L.
Published: May 2006

Two populations of
Avena barbata
have been sampled intensively and allelic frequencies have been determined on a fine grid for six enzyme loci. The distribution of alleles among microniches within the location occupied by one of these populations (CSA-1) was correlated with environment following patterns of macro- and microdifferentiation previously described in California. Multilocus analyses revealed striking gameticphase disequilibrium for both linked and unlinked loci, and also that two balanced five-locus gametic types, one associated with mesic conditions and the other with more xeric conditions, are in substantial excess at the CSA-1 location. Evidence is presented that these two gametic types are maintained by selection acting on two coadapted combinations of alleles, held together by restriction of recombination resulting from linkage and/or inbreeding. Gametic-phase disequilibrium featuring different allelic complexes were found in each of three microniches in the second population (Geyserville), which occupies a site that is environmentally atypical for
A. barbata
.
Elongation Factor T-Dependent Hydrolysis of Guanosine Triphosphate Resistant to Thiostrepton
Authors: Ballesta Juan P. G. , Vazquez David
Published: May 2006

Methanol stimulates the hydrolysis of GTP catalyzed by bacterial ribosomes in the presence of the chain elongation factor T (EF-T). The methanol-stimulated activity is uncoupled from aminoacyl-tRNA binding to the ribosomes and does not require the presence of either synthetic polynucleotide messenger or aminoacyl-tRNA. When these reactants are present, along with EF-T, GTP, and methanol, the ribosomal binding of aminoacyl-tRNA is inhibited by thiostrepton but the uncoupled, EF-T-dependent hydrolysis of GTP is resistant to the antibiotic.
Enhancement of RNA Polymerase Activity by a Factor Released by Auxin from Plasma Membrane
Authors: Hardin James W. , Cherry Joe H. , Morré D. James , Lembi Carole A.
Published: May 2006

Using recently developed techniques for solubilization of RNA polymerase from soybean chromatin and isolation of plasma membrane fractions from plants we can show the presence of a transcriptional factor specifically released from the membranes by auxin, 2,4-dichlorophenoxyacetic acid. The nonauxin, 3,5-dichlorophenoxyacetic acid, does not release the factor, but subsequent exposure of the membranes to auxin results in its release. Factor activity could not be demonstrated in fractions devoid of plasma membranes. The presence of a regulatory factor for RNA polymerase associated with plant plasma membrane and specifically released by auxin provides a mechanism whereby both rapid growth responses and delayed nuclear changes could be derived from a common auxin receptor site associated with plasma membrane.
Induction of Neuronal Functions: Acetylcholine-Induced Acetylcholinesterase Activity in Mouse Neuroblastoma Cells
Authors: Harkins Jane , Arsenault Molly , Schlesinger Kurt , Kates Joseph
Published: May 2006

Addition of acetylcholine to growing cultures of mouse neuroblastoma cells induced a 37-fold increase in the specific activity of acetylcholinesterase (EC 3.1.1.7). Morphological changes, consisting of neurite-extensions, were also observed during the logarithmic phase of growth of cells stimulated with acetylcholine. A histochemical procedure for localization of acetylcholinesterase was used with the following results: (
a
) Cells differentiating by growth inhibition in serum-free medium do not stain positively for acetylcholinesterase, except when they have extended neurites, whereas all cells induced with acetylcholine, with or without neurites, stain positively for the enzyme. (
b
) The inverse relation between cell growth and induction of enzyme activity was demonstrated in nondividing cells at the center of a colony that do not incorporate thymidine into DNA and that stain positively for acetylcholinesterase, whereas actively dividing cells on the periphery of the colony do not stain for the enzyme. However, by addition of acetylcholine we were able to dissociate inhibition of cell growth from biochemical and morphological differentiation in mouse neuroblastoma cells.
Acetylcholine Receptors of Muscle Grown
In Vitro
Authors: Vogel Z. , Sytkowski A. J. , Nirenberg M. W.
Published: May 2006

[
125
I]Monoiodo- and [
125
I]diiodo-α-bungarotoxin were synthesized and shown to bind specifically to the acetylcholine receptor of cultured embryonic chick- and rat-muscle cells. The pharmacologic properties of the receptor of cultured embryonic chick muscle resembled those of the nicotinic acetylcholine receptor of adult vertebrate muscle. Autoradiography of muscle cells labeled with toxin showed that acetylcholine receptors were distributed over the entire cell surface. In addition, discrete areas with a high receptor concentration were found.
Structure of the Oxidized Form of a Flavodoxin at 2.5-Å Resolution: Resolution of the Phase Ambiguity by Anomalous Scattering
Authors: Watenpaugh K. D. , Sieker L. C. , Jensen L. H. , Legall J. , Dubourdieu M.
Published: May 2006

Flavodoxin from
Desulfovibrio vulgaris
crystallizes in the oxidized form as well-formed, tetragonal bipyramids, space group P4
3
2
1
2, unit-cell parameters,
a = b
= 51.6 Å,
c
= 139.6 Å, 8 molecules per unit cell.

The structure has been determined at 2.5-Å resolution with phases based on a single isomorphous derivative. The phase ambiguity of a single derivative was resolved by use of anomalous scattering from the single-site Sm
+3
.

The molecule has a five-strand pleated sheet core with two long helices on either side of the sheet. The flavin mononucleotide lies mostly buried on one side of the molecule, but the methyl groups, one edge of the flavin, and part of the ribityl are exposed at the surface.
Specificity of the Break Produced by Restricting Endonuclease R
1
in Simian Virus 40 DNA, as Revealed by Partial Denaturation Mapping
Authors: Mulder Carel , Delius Hajo
Published: May 2006

Superhelical circular (form I) SV40 DNA was converted to linear molecules by the action of a partially purified restriction enzyme of Resistance Transfer Factor-R
1
of
Escherichia coli
. The resulting linear DNA molecules are full length, as judged by their sedimentation through alkaline sucrose gradient and by direct observation in an electron microscope. Nicked circular (form II) DNA was found as an intermediate in the conversion of form I DNA to linear DNA. Analysis of partial denaturation maps obtained by alkaline denaturation of the unitlength linear molecules showed that the break in SV40 DNA occurred at a specific site on the DNA.
Conversion of ϕX174 and fd Single-Stranded DNA to Replicative Forms in Extracts of
Escherichia coli
Authors: Wickner Reed B. , Wright Michel , Wickner Sue , Hurwitz Jerard
Published: May 2006

ϕX174 and M13 (fd) single-stranded circular DNAs are converted to their replicative forms by extracts of
E. coli pol
A1 cells. We find that the ϕX174 DNA-dependent reaction requires Mg
++
, ATP, and all four deoxynucleoside triphosphates, but not CTP, UTP, or GTP. This reaction also involves the products of the
dna
C,
dna
D,
dna
E (DNA polymerase III), and
dna
G genes, but not that of
dna
F (ribonucleotide reductase). The
in vitro
conversion of fd single-stranded DNA to the replicative form requires all four ribonucleoside triphosphates, Mg
++
, and all four deoxynucleoside triphosphates. The reaction involves the product of gene
dna
E but not those of genes
dna
C,
dna
D,
dna
F, or
dna
G. The reaction with fd DNA is inhibited by rifampicin or antibody to RNA polymerase, while the reaction with ϕX174 DNA is not affected by either. With the ϕX174 DNA-dependent reaction, activities have been detected that specifically complement extracts of
dna
A,
dna
B,
dna
C,
dna
D, or
dna
G mutants.
Autonomy or Nonautonomy of Gene Effects in Mosaics
Authors: Tokunaga Chiyoko
Published: May 2006

The dominant autosomal gene
Msc
(
Multiple sex combs
) of
Drosophila
causes the appearance of sex combs on the second and third legs and a reduction of size of sex combs on first legs. The effect of
Msc
was studied in mosaic flies in which non-
Msc
spots were present on a
Msc
background. Mosaics were due to somatic crossing-over induced by x-rays. Analysis of mosaics suggested autonomy of the action of
Msc
, provided that the somatic crossing-over occurs less frequently proximally to the
Msc
locus than distally. This unusual ratio of somatic crossing-over was confirmed by a separate experiment with the gene
Kinked
, whose locus is very close to
Msc
.
Coenzymatic Activity of Pyridoxal 5′-Sulfate and Related Analogues of Pyridoxal 5′-Phosphate
Authors: Groman E. , Huang Y. Z. , Watanabe T. , Snell Esmond E.
Published: May 2006

The effect of changes in the substituent at the 5′-position of pyridoxal 5′-phosphate on the coenzymatic activity of six analogues of this coenzyme was determined for three bacterial enzymes. Pyridoxal 5′-sulfate showed substantial coenzymatic activity for arginine decarboxylase and tryptophanase, but not for D-serine dehydratase; α
5
-pyridoxalmethylphosphonate showed substantial activity for D-serine dehydratase, but not for the other two enzymes. These results demonstrate that neither the dianionic phosphate group nor the ester oxygen of pyridoxal 5′-phosphate is a general requirement for coenzymatic activity. Minor variations in orientation and charge of the group at position 5 exert major effects on the capacity for complex formation between analogue and apoenzyme, and on the catalytic efficiency of the resulting complex, but have comparatively little effect on the substrate affinity of the analogue-apoenzyme complexes. These effects show no general pattern from enzyme to enzyme, and do not correlate with the affinity of analogue for apoenzyme under the conditions tested.
A Pressor Substance in the Cerebrospinal Fluid of Normotensive and Hypertensive Patients
Authors: Finkielman Samuel , Fischer-Ferraro Catalina , Diaz Alberto , Goldstein Daniel J. , Nahmod Victor E.
Published: May 2006

A pressor polypeptide was isolated from the cerebrospinal fluid of normotensive and hypertensive patients. Pharmacologically it behaves like angiotensin I. A very significant correlation (
r
= 0.83,
P
< 0.001) was found between the concentration of this polypeptide and the blood pressure of essential hypertensive patients.
Role of the Penicillin-Sensitive Transpeptidation Reaction in Attachment of Newly Synthesized Peptidoglycan to Cell Walls of
Micrococcus luteus
Authors: Mirelman David , Bracha Rivka , Sharon Nathan
Published: May 2006

Cell-wall preparations of
Micrococcus luteus
(
lysodeikticus
) catalyze
in vitro
peptidoglycan synthesis from UDP
N
-acetyl-D-glucosamine, UDP
N
-acetylmuramic acid-pentapeptide, and glycine. Newly synthesized peptidoglycan is partially cross-linked by a transpeptidation reaction with concomitant release of C-terminal D-alanine. Penicillin not only strongly inhibits release of D-alanine (98% at 1 μg/ml), but also markedly inhibits incorporation of acetylglucosamine and
N
-acetylmuramic acid-pentapeptide into the preformed cell-wall peptidoglycan. The simplest explanation for the results is that incorporation of newly synthesized strands of peptidoglycan and their attachment to “older” cell-wall peptidoglycan proceeds mainly by transpeptidation and that transglycosylation is responsible only for part of the elongation of the pre-existing peptidoglycan. Another possibility is that incorporation occurs by transglycosylation, but it cannot continue without concurrent formation of peptide cross-bridges.
Cleavage of Simian Virus 40 DNA at a Unique Site by a Bacterial Restriction Enzyme
Authors: Morrow John F. , Berg Paul
Published: May 2006

The R
1
restriction endonuclease of
Escherichia coli
converts covalently-closed circular Simian Virus 40 (SV40) DNA to unit-length linear duplex molecules. Cleavage occurs at a unique site, since denaturation and renaturation of these linear molecules yield linear but no circular molecules. The distance from the cleavage site to the SV40 DNA sequence contained in the adenovirus-SV40 hybrid, Ad2
+
ND
1
, is 0.11 of the length of SV40 DNA. T4 gene 32 protein binds to SV40 DNA in a region 0.45 of the length of SV40 DNA from the R
1
cleavage site.
E. coli
B restriction endonuclease can cleave SV40 DNA at several sites.
An Asymbiotic Nitrogen-Fixing Bacterium from the Root Environment of Corn
Authors: Raju P. N. , Evans Harold J. , Seidler Ramon J.
Published: May 2006

Examination of root systems and adhering soil associated with unusually green corn plants from nitrogen-deficient areas in fields has revealed higher acetylene-reducing activities than comparable root systems of chlorotic plants that appeared to be nitrogen deficient. From the root systems with acetylene-reducing activity, N
2
-fixing
Enterobacter cloacae
were isolated. Pure cultures of the organism grown in a medium lacking added fixed nitrogen reduced acetylene to ethylene and used N
2
as a sole source of nitrogen under anaerobic conditions. Acetylene reduction was strikingly inhibited by 0.04 atm or greater partial pressures of O
2
; however, the bacteria maintained appreciable acetylene-reducing rates in medium exposed to partial pressures of O
2
ranging from 0.005 to 0.015 atm. Nitrogenase activity in cell-free extracts of the bacterium was dependent upon Na
2
S
2
O
4
and an ATP-generating system. Some environmental conditions expected to influence N
2
fixation by free-living N
2
-fixing bacteria on root surfaces of nonlegumes are discussed.
Mutants That Produce Nitrogenase in the Presence of Ammonia
Authors: Gordon Joyce K. , Brill Winston J.
Published: May 2006

Mutants of
Azotobacter vinelandii
that fix N
2
in the presence of excess NH
4
+
have been isolated. A mutant that was unable to synthesize component I and component II of nitrogenase was spontaneously reverted to the N
2
-fixing phenotype. Of 21 revertants picked, 7 revertants were not as sensitive as the wild type to repression. A derepressed mutant is as sensitive as the wild type to growth inhibition by 2-methylalanine in the presence of glucose.
Axial Presentations of Regular Arcs on M

n
Authors: Morse Marston
Published: May 2006

THEOREM 1.

Let M
n
be a Riemannian manifold of class C
m
, m > 0. On M
n
let g be a simple compact, sensed, regular arc whose local coordinates are functions of class C
m
of the algebraic arc length s, measured along g from a prescribed point of g. There then exists a presentation (F: U, X) [unk] [unk]M
n
such that g [unk] X, and each point p(s) of g is represented in the euclidean domain U by coordinates (x
1
,...,x
n
) = (s,0,...,0)

.
Replacement of Nerve-Growth Factor by Ganglionic Non-Neuronal Cells for the Survival
In Vitro
of Dissociated Ganglionic Neurons
Authors: Burnham Patricia , Raiborn Charles , Varon Silvio
Published: May 2006

Nerve-growth factor is known to cause a considerable increase in the number of neurons putting out processes and surviving in cell cultures of dissociated dorsal-root and sympathetic ganglia from embryonic chicks. Similar effects of nerve-growth factor have now been noted with cultures of dissociated dorsal-root ganglia from newborn mice or rats. In all three sensory ganglionic systems, the effects of the nerve-growth factor on fiber production and neuronal survival could be mimicked, in the absence of the factor, by adequate increase of the non-neuronal cells in the cultures. The results suggest a hypothesis that views the role of the nerve-growth factor as subordinate to that of the non-neuronal cells.
Time-Variant Conductance of Bilayer Membranes Treated with Monazomycin and Alamethicin
Authors: Mauro A. , Nanavati R. P. , Heyer E.
Published: May 2006

Experimental data obtained on bilayer membranes treated with either of two antibiotics, monazomycin or alamethicin, are presented showing the marked difference in the time course of the rise and subsequent decay of the conductance in response to a positive and negative step of potential established by means of a voltage-clamp feedback circuit. The variation of the conductance with time in these model systems qualitatively mimics the behavior of the “potassium conductance” of squid giant axons and other excitable biological systems; namely, the rise of the conductance to the steady state requires a longer time than its decay to the resting state. For the alamethicin system, the decay time becomes very brief—as short as 50 μsec—as either the salt or the alamethicin concentration is reduced, while the rise time remains several seconds. This marked brevity of the decay time versus the rise time may have implications for the mechanism underlying the formation of conducting channels in such membranes.
The Three-Dimensional Structure of Yeast Phenylalanine Transfer RNA: Shape of the Molecule at 5.5-Å Resolution
Authors: Kim S. H. , Quigley G. , Suddath F. L. , McPherson A. , Sneden D. , Kim J. J. , Weinzierl J. , Blattmann P. , Rich Alexander
Published: May 2006

Three isomorphous heavy-atom derivatives have been obtained of orthorhombic crystals of phenylalanine transfer RNA from yeast. These derivatives contain osmium, samarium, and platinum. The positions of the heavy atoms have been determined; these have been used to calculate a three-dimensional electron-density map of transfer RNA at a resolution of 5.5 Å. The map shows a high contrast between the molecular boundaries and the solvent areas, so that most of the external shape of the molecule can be determined. The molecule appears to be 92 Å long and to have a width varying from 16 Å to 34 Å. There are some narrow regions in the molecule that connect more globular regions. The electron density map shows chains of dense objects approximately 6 Å apart that are probably due to adjacent phosphate groups on the polynucleotide chain. At the present stage of the analysis it is not possible to trace the entire backbone unambiguously; however, the data at this resolution suggest no apparent similarity between the folding of the molecule and any of the tertiary structure models proposed for transfer RNA.
Structural and Functional Properties of Ribosomes Crosslinked with Dimethylsuberimidate
Authors: Slobin Lawrence I.
Published: May 2006

To test whether a 30S ribosomal subunitformylmethionyl-tRNA-mRNA complex is an obligatory intermediate in protein synthesis, 70S ribosomes from
Escherichia coli
were crosslinked with the bifunctional imidoester, dimethylsuberimidate. Crosslinked ribosomes contained covelently joined 30S and 50S subunits, as judged by their inability to dissociate at low Mg
2+
concentrations. Treatment of 70S ribosomes with high salt (1 M NH
4
Cl), either before or after reaction with the crosslinking reagent, produced two different crosslinked ribosomal particles, one of “60 S” and the other “70 S.” Preliminary evidence indicates that both particles can bind
N
-acetylphenylalanyl-tRNA at low Mg
2+
concentrations and are active for polyphenylalanine syntheses.

Crosslinked ribosomes were functional when tested with poly(U) as an mRNA in systems requiring initiation factors and
N
-acetylphenylalanyl-tRNA for activity. Under optimal crosslinking conditions, they retained 80% of the activity of unmodified ribosomes for polyphenylalanine synthesis. Despite the maintenance of these functional capacities, such ribosomes had a sharply reduced ability to bind fMet-tRNA and were completely inactive in protein synthesis with bacteriophage f2 RNA as a messenger. We conclude that 70S ribosomes must dissociate into subunits to initiate protein synthesis with natural mRNAs.
Altered Chloroplast Ribosomal Proteins Associated with Erythromycin-Resistant Mutants in Two Genetic Systems of
Chlamydomonas reinhardi
Authors: Mets Laurens , Bogorad Lawrence
Published: May 2006

The phenotype of several erythromycin-resistant mutants of
Chlamydomonas reinhardi
was further characterized in terms of the electrophoretic properties of their chloroplast ribosomal proteins. In mutant
ery-M2d
a single protein of the large (52 S) subunit has altered properties, which probably result from a change in its primary sequence. This mutation is inherited in a Meudelian manner. In mutant
ery-U1a
, which is inherited in a uniparental manner, a different single protein of the 52 S subunit is altered. This change might result from a change in either the primary sequence of the protein or in some form of secondary modification. These results indicate that these two distinct genetic systems must cooperate in the production of chloroplast ribosomes.
Fluorescence Studies of the Binding of the Polyene Antibiotics Filipin III, Amphotericin B, Nystatin, and Lagosin to Cholesterol
Authors: Bittman Robert , Fischkoff Steven A.
Published: May 2006

The interactions of filipin III, amphotericin B, nystatin, and lagosin with sterols in aqueous suspension and in vesicles were followed by fluorescence excitation spectra and by measurement of polarized fluorescence intensities. The equilibrium constants for association of the polyene antibiotics with aqueous suspensions of cholesterol follow the order filipin III > amphotericin B > nystatin > lagosin, in agreement with the order reported for the extent of damage these antibiotics cause in natural and model membranes. Fluorescence polarization measurements show that hydrophobic forces are primarily responsible for the formation of the complexes. Filipin III undergoes a large enhancement in fluorescence polarization on binding to aqueous suspensions of cholesterol and
epi
-cholesterol, and to vesicles of lecithin-cholesterol, lecithin-β-cholestanol, and lecithinergosterol. Small increases in polarization occur on interaction of filipin III with vesicles derived from lecithin and
epi
-cholesterol, thiocholesterol, and androstan-3β-ol. Amphotericin B undergoes a relatively constant enhancement in fluorescence polarization on interaction with the various lecithin-sterol vesicles used and does not display the selectivity exhibited by filipin III. It is suggested that filipin III serves as a probe of lecithin-sterol interaction.
Mechanism of Cooperative Oxygen Binding to Hemoglobin
Authors: Ogata Ronald T. , McConnell Harden M.
Published: May 2006

Evidence is presented that a generalized concerted transition model provides a quantitative understanding of (
a
) the molecular species that are present in solutions of partially liganded hemoglobin and (
b
) the macromolecular mechanism of cooperativity. Model parameters for hemoglobin A and for hemoglobin Chesapeake were determined from studies of the binding of spin-label triphosphates to ligand-free and partially liganded hemoglobin solutions, and to the hybrids α
2
+CN
β
2
and α
2
β
2
+CN
. This model is the same as that proposed originally by Monod, Wyman, and Changeux [
J. Mol. Biol.
(1965) 12, 88] for hemoglobin, except that the α-subunits are treated as nonequivalent to the β-subunits.
Activity of Ribosomes Containing 5S RNA with a Chemically Modified 3′-Terminus
Authors: Fahnestock S. R. , Nomura M.
Published: May 2006

Ribosomes containing 5S RNA in which the 3′-terminus has been modified chemically, either by periodate oxidation or by conversion of the terminal ribose to a morpholine derivative, are fully as active in peptidebond formation and polypeptide synthesis as those ribosomes with unmodified 5S RNA. These results exclude models for protein synthesis in which peptidyl-5S RNA is formed as an intermediate.
A New Micromethod for Evaluating Lymphocyte Responses to Phytohemagglutinin: Quantitative Analysis of the Function of Thymus-Dependent Cells
Authors: Park B. H. , Good R. A.
Published: May 2006

We have developed a new micromethod for testing phytohemagglutinin stimulation of human lymphocytes. 50 μl of peripheral blood is incubated at 37°C directly, without cell separation, with 50 μl of tissue culture medium containing 50μg of phytohemagglutinin for 24 hr. Then, 0.5 μCi of tritiated thymidine in 50 μl of tissue culture medium is added and incubated for an additional 16 hr. After incubation, erythrocytes are selectively lysed in distilled water, and white blood cells are trapped quickly on a Millipore filter. The radioactivity of the filter is then assessed by a scintillation counter. The requirement of extremely small amounts of blood and a short incubation time are advantages. Further, this method provides a most useful evaluation of thymusdependent cell populations in man and experimental animals and, for the first time, this method provides the possibility of quantitating the deficiency of thymus-dependent cells.
Action of DNA Polymerase I of
Escherichia coli
with DNA-RNA Hybrids as Templates
Authors: Karkas John D. , Stavrianopoulos Jannis G. , Chargaff Erwin
Published: May 2006

Experiments indicating the ability of the ribo strand of a DNA-RNA template to guide polydeoxynucleotide synthesis by highly purified DNA polymerase I of
E. coli
(EC 2.7.7.7) are presented. With poly(rA)·poly(dT) as template, poly(dT) is formed with a high efficiency, but almost no poly(dA). The specific activity of the enzyme, when tested with this template under suitable conditions, is eight times greater than that found for the poly(dA-dT) template. Single-stranded DNA fractions, with no template activity for DNA polymerase, are converted to efficient templates after their transcription by RNA polymerase. A concerted polymerization reaction, in which the action of DNA polymerase is dependent on that of RNA polymerase, can also be demonstrated with synthetic polydeoxynucleotides and single-stranded fractions of denatured DNA as templates.
The Inhibition of Plant and Animal Adenosine 3′:5′-Cyclic Monophosphate Phosphodiesterases by a Cell-Division-Promoting Substance from Tissues of Higher Plant Species
Authors: Wood Henry N. , Lin Michael C. , Braun Armin C.
Published: May 2006

One member of a new class of cell-division-promoting factors, that has been given the trivial name of cytokinesin I, is a potent inhibitor of adenosine 3′:5′-cyclic monophosphate phosphodiesterases of both plant and animal origin. Since an adenylate cyclase has been demonstrated in this study to be present in plant cells, the results suggest that cytokinesin I may be exerting its biological effects in promoting division in cells of higher plant species as a regulator of adenosine 3′:5′-cyclic monophosphate.
Direct Evidence for a Prostaglandin Receptor and Its Application to Prostaglandin Measurements
Authors: Kuehl F. A. , Humes J. L.
Published: May 2006

A prostaglandin receptor is present in rat adipocytes, as shown by competition studies with [
3
H]-prostaglandin E
1
. The affinity of the E prostaglandins for this receptor preparation is greater than that of A and F prostaglandins, an observation consistent with their relative potencies in stimulating cyclic AMP formation in isolated mouse ovaries and various other organs. In the protocol described, binding constants of 3-8 nM were obtained with prostaglandins E
2
and E
1
. A sensitivity of 1 pmole makes this method readily applicable for measurement of tissue concentrations of the E prostaglandins.
Stimulation by Dopamine of Adenylate Cyclase in Retinal Homogenates and of Adenosine-3′:5′-Cyclic Monophosphate Formation in Intact Retina
Authors: Brown Joan Heller , Makman Maynard H.
Published: May 2006

A catecholamine-sensitive adenylate cyclase system is present in homogenates of both calf and rat retinas. Dopamine is a more potent activator of the bovine enzyme than is norepinephrine or epinephrine. Cyclic AMP concentrations in intact bovine retina are increased by dopamine, as well as by other catecholamines, and by depolarizing agents. Studies with adrenergic blocking agents suggest that the stimulation of retinal adenylate cyclase by catecholamines cannot be clearly defined in terms of the characteristics of alpha or beta adrenergic receptors. Bovine retina also contains a protein kinase that is stimulated 20-fold by cyclic AMP. It is proposed that dopamine is the major activator of a retinal adenylate cyclase, and that this activation is related to its role as a neurotransmitter.
Heavy Meromyosin: Evidence for a Refractory State Unable to Bind to Actin in the Presence of ATP
Authors: Eisenberg Evan , Dobkin Louis , Kielley W. Wayne
Published: May 2006

The binding of actin to heavy meromyosin (HMM) in the presence of ATP was studied by analytical ultracentrifuge and ATPase studies. At 0°C, at very low ionic strength, the double-reciprocal plot of HMM ATPase against actin concentration is linear. If one assumes that all of the HMM is bound to actin when the ATPase activity equals
V
max
, then, at an actin concentration where the actin-HMM ATPase is 85% of
V
max
, all but 15% of the HMM should be complexed with actin. However, when the binding of HMM to actin in the presence of ATP was measured with the analytical ultracentrifuge, more than 60% of the HMM was not bound to actin. From experiments with EDTA- and Ca-ATPases it seemed unlikely that the unbound HMM was denatured. It is thus possible that during the steady-state hydrolysis of ATP, HMM spends more than 50% of its cycle of interaction with actin and ATP in a “refractory state,” unable to bind to actin, i.e., while an HMM molecule goes through one cycle of interaction with actin and ATP, an actin monomer could bind and release several HMM molecules so that the turnover rate per mole of added actin would be considerably greater than that per mole of added HMM. Comparison of the rate of ATPase activity at very high actin concentration with that at very high HMM concentration shows that this is indeed so. Therefore, both kinetic and ultracentrifuge studies suggest that the HMM exists in a refractory state during a large part of its cycle of interaction with actin and ATP.