bluuebunny/crossref_metadata_2025 huggingface dataset:
Oligoclonal IgG Antibody Response in the Central Nervous System to Different Measles Virus Antigens in Subacute Sclerosing Panencephalitis
Authors: Vandvik Bodvar , Norrby Erling
Published: May 2006

Agarose electrophoresis of cerebrospinal fluid from two patients with subacute sclerosing panencephalitis revealed in both cases several homogeneous bands in the intermediate and basic gammaglobulin region. The bands were identified as IgG with various degrees of kappa or lambda light-chain restriction in crossed immunoelectrophoresis.

Homogeneous IgG bands were separated by preparative agarose electrophoresis and were found to represent measles virus-specific antibodies. Antibody activities against different virus products (hemolysin, hemagglutinin, and nucleocapsids) were carried by different populations of IgG. In both cerebrospinal fluid materials, antibodies to the virus hemolysin and to virus nucleocapsids were found to be relatively more basic than the antibodies to virus hemagglutinin, which appeared in the basic intermediate gammaglobulin region.

We conclude that the oligoclonal IgG bands in cerebrospinal fluid of patients with subacute sclerosing panencephalitis represent homogeneous measles virus antibodies. In some instances, the IgG bands appeared to fulfill criteria of monoclonality on the basis of their electrophoretic homogeneity, selective light-chain type, and specific antibody activity.
Activation of Prolyl Hydroxylase in L-929 Fibroblasts by Ascorbic Acid
Authors: Stassen Frans L. H. , Cardinale George J. , Udenfriend Sidney
Published: May 2006

The addition of ascorbate to the culture medium of early log-phase mouse fibroblasts (L-929 cells) resulted in a 5-fold increase of prolyl hydroxylase activity. Maximal activity was reached within 2 hr after addition of 5 μM ascorbate. The total amount of enzyme-related antigen did not change on treatment with ascorbate and the activation was shown to be independent of RNA and protein synthesis. The increase in activity caused by ascorbate is therefore due to the activation of a preformed precursor. Enzyme (molecular weight 260,000-300,000) and putative precursor (molecular weight 85,000-105,000) were separated by chromatography on DEAE-Sephadex. Treatment of intact cells with dithiothreitol resulted in an almost quantitative conversion of the enzyme to the smaller inactive protein. When these cells were treated with ascorbate or incubated overnight in fresh medium the enzyme reappeared and precursor concentrations decreased proportionately. Ascorbate may act by bringing about aggregation of enzymatically inactive subunits.
Diazoacetyl Subtilisin
Authors: Stefanovsky Yuri , Westheimer F. H.
Published: May 2006

Subtilisin reacts at pH 6.8-7.8 with
p
-nitrophenyl diazoacetate to release
p
-nitrophenol and form diazoacetyl subtilisin. Although at pH 7.8 this derivative rapidly undergoes hydrolytic cleavage to regenerate active enzyme, the derivative can be trapped by rapidly lowering the pH to 5. Similarly, with
14
C-labeled
p
-nitrophenyl diazoacetate, the corresponding radiochemically labeled diazoacetyl enzyme can be prepared. Photolysis of this radioactive derivative incorporates radioactivity into the protein, and subsquent hydrolysis gives rise to several radioactive components, which, however, have not yet been identified.
The 3′-Terminal Nucleotide Sequences of Bacteriophage λ DNA
Authors: Weigel Paul H. , Englund Paul T. , Murray Kenneth , Old Robert W.
Published: May 2006

Analyses of radioactive oligonucleotides in endonuclease digests of 3′-terminally labeled λ DNA revealed the 3′ terminal sequence -GTTACG for the
l
strand and -ACCCGCG for the
r
strand. These sequences, together with those previously known for the 5′ cohesive ends, provide a total of 25 known base-pairs in the vicinity of the termini. When the cohesive ends are paired, the sequence between the nicks can be bisected by a 2-fold rotational axis of symmetry. Five of the first eight base-pairs, on either side of the axis, are rotationally symmetric. This symmetry may be involved in the recognition of the site by an enzyme responsible for formation of the cohesive ends.
Fusion of Phospholipid Vesicles with Viable
Acholeplasma laidlawii
Authors: Grant C. W. M. , McConnell Harden M.
Published: May 2006

When vesicles of dipalmitoyl phosphatidylcholine produced by sonication are mixed with
Acholeplasma laidlawii
in neutral buffer, a phenomenon occurs that is most readily explained in terms of fusion of lipid vesicle membrane with the mycoplasma cytoplasmic membrane. The mycoplasma can readily accumulate large quantities of the foreign lipid without loss of viability. The added lipids do not remain in patches but diffuse laterally throughout the mycoplasma membrane.
Human Regulatory Gene for Inducible Tyrosine Aminotransferase in Rat-Human Hybrids
Authors: Croce Carlo M. , Litwack Gerald , Koprowski Hilary
Published: May 2006

The inducibility of tyrosine aminotransferase (EC 2.6.1.5) by corticosteroid hormones in rat-human hybrid clones was studied. The presence of human X chromosome activity in the cells was always associated with the suppression of tyrosine aminotransferase inducibility in all the clones examined. Negative correlation between the human X chromosome and inducibility of the enzyme was clearly established. Corticosteroid receptor was present to the same extent in hybrid cell clones that either contained or lost the human X chromosome. The human repressor for inducible tyrosine aminotransferase has a linkage relationship with glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and hypoxanthine-guanine-phosphoribosyltransferase (EC 2.4.2.8) and, therefore, can be assigned to the X chromosome.
Effect of Insulin on the Growth Pattern and Adenylate Cyclase Activity of BHK Fibroblasts
Authors: De Asúa Luis Jiménez , Surian Estela S. , Flawia Mirtha M. , Torres Héctor N.
Published: May 2006

BHK 21/13 fibroblasts grown in the presence of insulin show some characteristics of a transformed strain. Cells broaden, cross each other intricately, and form colonies on both polystyrene dishes and soft agar. The effect of insulin is prevented by addition of
N
6
-butyryl adenosine 3′:5′-cyclic monophosphate and theophylline to the culture medium. Insulin causes a decrease in the concentration of intracellular adenosine 3′:5′-cyclic monophosphate and inhibition of adenylate cyclase activity in BHK fibroblast membranes. This inhibition is observed at insulin concentrations of 0.1 nM or higher.
Mapping of
Escherichia coli
Ribosomal Components Involved in Peptidyl Transferase Activity
Authors: Sonenberg N. , Wilchek M. , Zamir A.
Published: May 2006

The method of affinity labeling has been used to identify protein components of 50S ribosomal subunits involved in peptidyl transferase activity.
E. coli
50S ribosomal subunits were mapped by reaction with the
N
-bromoacetyl analog of chloramphenicol, an antibiotic known to interact specifically with the active center of the enzyme. The synthetic analog competes with chloramphenicol in binding to 50S ribosomal subunits and inhibits peptidyl transferase activity. It attaches covalently to the ribosome under appropriate conditions and causes an irreversible loss in peptidyl transferase activity. The reagent specifically alkylates cysteine residues of proteins L2 and L27.
Mutational Analysis of a Regulatory Gene for Morphogenesis in
Schizophyllum
Authors: Raper Carlene A. , Raper John R.
Published: May 2006

Knowledge of the structure and function of a complex gene regulating sexual development in the mushroom,
Schizophyllum commune
, has come from the analysis of various mutations in a chromosomal region known as the
B
β incompatibility gene. This gene is one of two linked genes,
B
α and
B
β, that together comprise the
B
factor which regulates a developmental sequence known as the
B
-sequence. The
B
-sequence is normally “turned off” unless alleles of different specificity of either
B
α or
B
β are combined in a heterokaryon resulting from the mating of two individuals. Various mutations have been found in the
B
β gene that range in effect from dominant,
always-on
, through a number of intermediate stages of changes in specificity and function, to recessive,
always-off
. There is evidence that the
B
β gene operates via a positive control mechanism and involves at least four functions, one of which has been shown to be separable by recombination.
Tropism of
Mycoplasma gallisepticum
for Arterial Walls
Authors: Clyde Wallace A. , Thomas Lewis
Published: May 2006

The fatal encephalopathy associated with
M. gallisepticum
strain S6 in turkey poults was completely curable by treatment with tylosin or pleuromutilin. The lesions of cerebral polyarteritis disappeared after therapy. Polyarthritis developed in some birds after recovery from encephalitis. Immunofluorescent studies revealed that intravenously injected organisms became localized as microcolonies within the walls of cerebral and periarticular arteries, and in the glomeruli. Turkey IgG deposition was demonstrated on the glomerular basement membranes, but not in the arterial lesions. The results suggest that the pathologic changes caused by this microorganism are due to selective localization and growth in arteries.
A Quantitative Assay for Intercellular Adhesion
Authors: Walther Bernt T. , Öhman Rolf , Roseman Saul
Published: May 2006

Intercellular adhesion is measured by a new method based on determination of the rates of attachment of single cells to confluent cell monolayers. The procedure is simple, rapid, and reproducible. Specific and nonspecific intercellular adhesions can be quantitated and distinguished from each other, and from the adhesion to glass (or plastic). The rate of adhesion of single cells to the monolayer is characteristic of more than 80% of the single-cell population. This method, therefore, provides a means for study of the molecular basis of intercellular adhesion.
Gap Junctions between Photoreceptor Cells in the Vertebrate Retina
Authors: Raviola Elio , Gilula Norton B.
Published: May 2006

In the outer plexiform layer of the retina the synaptic endings of cone cells make specialized junctions with each other and with the endings of rod cells. The ultrastructure of these interreceptor junctions is described in retinas of monkeys, rabbits, and turtles, in thin sections of embedded specimens and by the freeze-fracturing technique. Cone-to-rod junctions are ribbon-like areas of close membrane approximation. On either side of the narrowing of the intercellular space, the junctional membranes contain a row of particles located on the fracture face A (cytoplasmic leaflet), while the complementary element, a row of single depressions, is located on fracture face B. The particle rows are surrounded by a membrane region that is devoid of particulate inclusions and bears an adherent layer of dense cytoplasmic material. Cone-to-cone junctions in some places are identical to cone-to-rod junctions, while in other places they closely resemble typical gap junctions (nexus). Interreceptor junctions, therefore, represent a morphological variant of the gap junction, and probably mediate electrotonic coupling between neighboring photoreceptor cells.
Biogenesis of Poxviruses: Inactivation of Host DNA Polymerase by a Component of the Invading Inoculum Particle
Authors: Pogo Beatriz G. T. , Dales Samuel
Published: May 2006

Inhibition of nuclear DNA polymerase activity in cells infected with vaccinia virus parallels the development of a nuclease activity similar to one associated with the virus particles. Both phenomena occur in the absence of protein synthesis, implying that incoming particles are responsible for the effects observed. Experimental evidence is presented indicating that the nuclear DNA polymerase activity is inhibited coincidentally with, and perhaps as a consequence of, the hydrolysis of nascent, single-stranded DNA molecules. Should this interpretation prove to be correct, our observations may have revealed the first instance in virus cytopathology linking the inactivation of a specific host-cell function with an enzyme activity originating from the invading particle.
A New Form of DNA Polymerase III and a Copolymerase Replicate a Long, Single-Stranded Primer-Template
Authors: Wickner William , Schekman Randy , Geider Klaus , Korǹberg Arthur
Published: May 2006

A new form of DNA polymerase III, termed Pol III star (Pol III
*
), has been purified to homogeneity from
Escherichia coli
. Pol III
*
is temperature sensitive when isolated from a thermo-sensitive
dna
E mutant, as had been described for Pol III. Pol III
*
and Pol III are separable by gel filtration. Pol III
*
utilizes a duplex template containing short gaps with the same catalytic properties as Pol III. However, Pol III
*
is able to replicate long, singlestranded templates such as homopolymer chains and viral circles of M13 and ϕX174 if provided with the following: spermidine, a primer fragment, and a new protein, termed copolymerase III
*
(Copol III
*
). The latter, purified to homogeneity, has no known independent enzymatic activity and supports synthesis by Pol III
*
but not by Pol I, Pol II, or Pol III.
Spin-State Correlations in Near Infrared Spectroscopy of Cytochrome c′
Authors: Kamen Martin D. , Kakuno T. , Bartsch R. G. , Hannon S.
Published: May 2006

Characteristic absorption spectra in the ultraviolet, visible, and near infrared regions are correlated with spin state in ferriheme proteins. Weak, diffuse bands in the near infrared exhibit maxima at about 1000-1100 nm (high spin) and at about 1450-1750 nm (low spin). In these and earlier studies such correlations have been established for several ferriheme proteins, but less extensively than in the more well-known cases of Soret and visible band maxima. We have strengthened the correlation in the near infrared by measurements of absorption spectra in
Rhodospirillum rubrum
cytochrome
c
′, a variant
c
-type cytochrome that exhibits a pH-induced transition from high-spin to low-spin state as the pH varies from 6.3 to 13.1. Data are provided on extinction coefficients of characteristic absorption bands at various pH values, obtained by comparison with those measured under the same conditions for horse-heart ferricytochrome
c
. It is concluded that good correlations of spin state with absorption behavior exist over the entire spectroscopic range from 250 to 2500 nm and that the basic assignments of absorption bands to in-plane charge transfer processes are consistent with these correlations.
Reconstitution of D-Lactate-Dependent Transport in Membrane Vesicles from a D-Lactate Dehydrogenase Mutant of
Escherichia coli
Authors: Reeves John P. , Hong Jen-Shiang , Kaback H. Ronald
Published: May 2006

Membrane-bound, flavin-linked D-lactate dehydrogenase in membrane vesicles of
E. coli
ML 308-225 is solubilized by extraction with guanidine HCl. When membrane vesicles prepared from a D-lactate dehydrogenase mutant are treated with this extract, they regain the capacity to catalyze D-lactate oxidation and D-lactate-dependent transport. Similar effects are obtained with wild-type membrane vesicles in which D-lactate oxidation and D-lactate-dependent transport have been inactivated by 2-hydroxy-3-butynoate. Although treatment of wild-type vesicles with the extract results in an increased capacity to catalyze D-lactate oxidation, no effect on transport is observed. Reconstituted transport activity is a saturable function of the amount of guanidine extract added. Moreover, the quantity of extract required to achieve maximum initial rates of transport varies with each transport system. On the other hand, reconstituted D-lactate oxidation increases linearly over a broader range of extract concentrations.

Oxamate, a competitive inhibitor of D-lactate dehydrogenase, and
p
-chloromercuribenzenesulfonate block both the initial rate of transport and the steady-state level of accumulation in reconstituted vesicles. Furthermore, these reagents induce efflux of transport substrates from preloaded, reconstituted vesicles. The same reagents inhibit the initial rate of uptake but not the steady-state level of accumulation in ML 308-225 vesicles, and do not induce efflux. These results suggest that, although reconstituted vesicles catalyze D-lactate oxidation and D-lactate-dependent transport, the system has not been reconstituted to its native state.
Determination of Secondary and Tertiary Structural Features of Transfer RNA Molecules in Solution by Nuclear Magnetic Resonance
Authors: Shulman R. G. , Hilbers C. W. , Wong Yeng P. , Wong K. Lim , Lightfoot Donald R. , Reid Brian R. , Kearns David R.
Published: May 2006

High-resolution 300-MHz proton nuclear magnetic resonance spectra of the hydrogen-bounded protons in three different purified tRNA molecules are presented. The resonances in the region between -11 and -15 ppm from 2,2-dimethyl-2-silapentane-5-sulfonate (DSS) are assigned to the ring NH protons of specific base pairs by two approaches. First, intrinsic positions of -14.8 ppm and -13.7 ppm are taken for the AU and GC ring NH protons, respectively, and the spectra are calculated by including ring current shifts from the nearest neighbors. The spectra calculated in this way on the basis of the cloverleaf are in good agreement with the observed. Second, fragments of yeast tRNA
Phe
were obtained, which helped in assignments of the spectrum of intact molecules. The close agreement strongly supports the cloverleaf model.

Tertiary structural features were determined in a few cases where the ring currents at the terminal base pairs of helical regions depended upon stacking of the helices. In this way, we were able to show that in
Escherichia coli
tRNA
Glu
the CCA stem forms a continuous helix with the TΨC stem, which is in accord with the preliminary x-ray structure of yeast tRNA
Phe
, suggesting that this stacking is observed in solution and may be a general property of different tRNA molecules. Similar reasoning suggests that in
E. coli
tRNA
fMet
G-27 is stacked upon the dihydrouridine helix.
Activation of a Covalent Enzyme-Substrate Bond by Noncovalent Interaction with an Effector
Authors: Malhotra O. P. , Bernhard Sidney A.
Published: May 2006

The absorption spectrum of an activesite specific chromophoric acyl enzyme, sturgeon β-(2-furyl)-acryloyl-glyceraldehyde-3-phosphate dehydrogenase, is reported. This acyl enzyme undergoes all of the catalyzed reactions characteristic of the intermediate of the physiological acyl enzyme, 3-phospho-D-glyceroyl-glyceraldehyde-3-phosphate dehydrogenease. The rates of reactions of both these acyl enzymes depend strongly on the
extent
of interaction of the acyl enzyme with the oxidized coenzyme, NAD
+
, even where the “redox” properties of the coenzyme are not required. Likewise, the spectral properties of chromophoric acyl enzyme are affected by the extent of bound NAD. Under the pseudophysiological conditions reported herein, there is a stoichiometric limitation of two furylacryloyl-acyl groups per enzyme molecule containing
four
covalently-equivalent subunits. The binding of NAD both to the apoenzyme and to the diacyl enzyme is heterogeneous: at low extents of NAD occupancy, NAD binding is stronger. The binding to acyl enzyme can be quantitatively described by an enzyme model involving a tetramer with 2-fold symmetry, and consequently containing equal numbers of
two
classes of sites. NAD binding to difurylacryloyl-enzyme occurs virtually discretely, first to the two unmodified (tight-binding) sites, followed by looser binding to the two acyl-sites. NAD occupancy at these latter sites transforms the chromophoric acyl spectrum from that characteristic of a model furylacryloyl-thiol ester in H
2
O to a highly perturbed furylacryloyl spectrum characteristic of monomeric native “active-thiol” furylacryloyl-enzymes. Likewise the acyl reactivity towards arsenolysis depends on the extent of NAD bound to the loose sites. Elimination of the tight binding of NAD to the difurylacryloyl enzyme tetramer by alkylation of the remaining two free SH groups with iodoacetate has no apparent influence on the NAD-dependent furylacryloyl-spectral perturbation at the “two
equivalent
acyl sites,” even though it eliminates the apparent “negative cooperativity” in NAD binding.
Chlorophyll Composition and Photochemical Activity of Photosystems Detached from Chloroplast Grana and Stroma Lamellae
Authors: Gasanov R. A. , French C. S.
Published: May 2006

A stroma fraction that has photosystem 1 activity and grana lamellae fractions that have activities for both photosystems were isolated by differential centrifugation of a needle valve homogenate. Subsequent fractions, corresponding to photosystems 1 (F-1D) and 2 (F-2D) were isolated by digitonin treatment of the grana lamellae (P-10K) and compared with respect to their chlorophyll composition and electron transport activities.

Fraction F-2D from grana lamellae having photosystem 2 activity is primarily active in photosystem 2 and contains only the four major forms of chlorophyll
a
with a predominance of chlorophyll
a
677 nm. This fraction differs from the original grana membranes in the absence of the longwavelength form of chlorophyll
a
and in the widening of the absorption band of chlorophyll
a
682 nm from 10.9 to 15.6 nm.

Photosystem 1 particles from grana and stroma both have high photosystem 1 activity but differ from each other in the proportions of the four major forms of chlorophyll
a
. The short-wavelength forms of chlorophyll
a
and also chlorophyll
b
650 nm in particles from grana lamellae comprise relatively more total area than these same forms in the particles from stroma. In addition, the fraction corresponding to photosystem 1 from grana lamellae is not shifted to the long-wavelength side of the main absorption maximum, as compared to the photosystem 2 particles from grana and the original grana membrane fraction; this is usually observed in fractions that have photosystem 1 activity. Furthermore, the longest wavelength form of chlorophyll
a
in the photosystem 1 particles from grana is at 700 nm, while in the same fraction from stroma, it is at 706 nm.

The half-width of the four main forms of chlorophyll
a
and both forms of chlorophyll
b
in the photosystem 1 fraction from grana is narrower than that of the corresponding forms in the same fraction from stroma. This may indicate a different packing of pigment molecules that are aggregated on the surface of membranes of these two fractions.
Chemical Synthesis and Biochemical Properties of Peptide Fragments of Apolipoprotein-Alanine
Authors: Sparrow James T. , Gotto Antonio M. , Morrisett Joel D.
Published: May 2006

Apolipoprotein-alanine is an apolipoprotein isolated from very-low-density lipoproteins of human plasma. This protein contains 79 amino acids and binds phosphatidyl choline. Four fragments of this molecule corresponding to sequence positions 41-79 (I), 48-79 (II), 55-79 (III), and 61-79 (IV) have been synthesized by standard solid-phase methods. The resulting peptides were cleaved from the resin and deblocked with liquid HF, then purified by chromatography on Sephadex G-50 and DEAE-cellulose. Each purified peptide eluted as a single, symmetrical peak, exhibited a single band on polyacrylamide gel electrophoresis, and gave an amino-acid analysis in good agreement with the theoretical value. Circular dichroism studies indicated that only fragments I and II became more helical in the presence of phosphatidyl choline and significantly inhibited the reactivation of delipidated β-hydroxybutyrate dehydrogenase (EC 1.1.1.30), an enzyme that requires phosphatidyl choline for activity. When subjected to ultracentrifugation at density 1.064 g/ml in the presence of phosphatidyl choline, fragments I, II, III, and IV floated to the top of the tube to the extent of 85, 50, 13, and 9%, respectively. These results indicate that residues 55-79 do not contain the minimum determinants required for the binding of phospholipid. However, extension of the peptide's N-terminus by seven residues produces a molecule that does bind phosphatidyl choline.
Nonribosomal Synthesis of Guanosine 5′,3′-Polyphosphates by the Ribosomal Wash of Stringent
Escherichia coli
Authors: Sy Jose , Ogawa Yasuo , Lipmann Fritz
Published: May 2006

A factor in the ribosomal wash of stringent strains of
E. coli
was identified by Haseltine
et al.
as a complement to the ribosomal system for the synthesis of the magic spot compounds of Cashel and Gallant. This factor has been found, in the absence of ribosomes, to catalyze the enzymatic pyrophosphoryl transfer from ATP to GTP or GTP in the formation of magic spot I and magic spot II, the guanosine tetra- and pentaphosphates (ppGpp and pppGpp), respectively. The enzyme, which normally requires the presence of the ribosome-tRNA-mRNA complex for activity, catalyzes a very slow synthesis that is stimulated tenfold by 20% methanol. The temperature optimum of the methanol-stimulated system is 25-30° and activity is drastically depressed at 37°, presumably by inactivation. Catalysis is linear with enzyme concentration and with time for the first 3 hr; during this period 25% of the added GTP is converted. The nonribosomal system is distinguished from the ribosomal system by having a lower Mg
++
and a higher NH
4
+
optimum. The two systems differ in their response to antibiotics: thiostrepton strongly inhibits the ribosomal system but has no effect on the nonribosomal system.
Measurements of Rates of Adenosine 3′:5′-Cyclic Monophosphate Synthesis in Intact
Escherichia coli
B
Authors: Peterkofsky Alan , Gazdar Celia
Published: May 2006

A method for labeling adenosine 3′:5′-cyclic monophosphate
in vivo
from precursor adenosine followed by quantitative analysis of the labeled nucleotide is described. When the labeling period is short and the specific activity of the ATP pool is determined, the rate of incorporation of radioactivity corresponds to a determination of adenylate cyclase activity
in vivo
. In
E. coli
B the specific activity of adenylate cyclase
in vivo
varies under different growth conditions. Under all conditions tested, the adenylate cyclase activity
in vivo
is great enough to account for the pattern of accumulation of cyclic AMP. This is in contrast to previous adenylate cyclase assays
in vitro
, where the measured enzyme activities were insufficient to account for the amounts of cyclic AMP accumulated.
Analysis of Long Pyrimidine Polynucleotides in HeLa Cell Nuclear DNA: Absence of Polydeoxythymidylate
Authors: Birnboim H. C. , Mitchel R. E. J. , Straus N. A.
Published: May 2006

HeLa cell nuclear DNA contains an unexpectedly large amount of long pyrimidine polynucleotides. These sequences were detected in DNA labeled with [
3
H] thymidine by treatment with formic acid-diphenylamine and subsequent analysis by polyacrylamide gel electrophoresis. About 0.5% of the total thymine residues were found in polynucleotides that migrated more slowly than 4S RNA. No polynucleotides of comparable size were detected in
Escherichia coli
DNA. The pyrimidine polynucleotides contained no pure poly(dT) sequences (less than 0.0015% of the total residues), as judged by thermal chromatography of a complex formed with poly(A).
A Ribosome Dissociation Factor from Rabbit Reticulocytes Distinct from Initiation Factor M
3
Authors: Merrick W. C. , Lubsen N. H. , Anderson W. F.
Published: May 2006

A ribosome dissociation factor (DF), from a 0.5 M KCl wash fraction of rabbit-reticulocyte-ribosomes, has been purified by Sephadex G-200, phosphocellulose, DEAE-cellulose, and hydroxyapatite chromatography. The most purified preparation displayed one major and several minor bands on 3.75% acrylamide gels.

DF cannot replace IF-M
1
, IF-M
2A
, IF-M
2B
, IF-M
2
, EF-1, or EF-2 in poly(U)-directed polyphenylalanine synthesis at low Mg
++
concentrations or in endogenous mRNA-directed globin synthesis. Conversely, these initiation and elongation factors showed little or no dissociation activity, even when assayed at levels 5-10 times greater than those required to saturate a polypeptide synthesis assay. Reticulocyte DF thus appears to be a distinct factor.
Isolation of a Glucagon-containing Peptide: Primary Structure of a Possible Fragment of Proglucagon
Authors: Tager Howard S. , Steiner Donald F.
Published: May 2006

The heterogeneity of crystalline bovine (ox)/porcine glucagon has been examined by gel filtration and ion-exchange chromatography. A strongly basic peptide that reacted well with antibodies to bovine/porcine glucagon was isolated and its primary structure was determined. The amino-acid sequence of the NH
2
-terminal 29 residues of the 4500-dalton peptide is identical with that of intact bovine or porcine glucagon. The remaining eight residues at its COOH-terminus are Lys-Arg-Asn-Asn-Lys-Asn-Ile-Ala. Small amounts of other glucagon-immunoreactive peptides having molecular weights ranging from 3700 to 9000 were also detected in crystals of bovine/porcine glucagon. We propose that the 37-residue peptide is a fragment of bovine or porcine proglucagon.
5-Bromo-2′-deoxyuridine Potentiation of Transformation of Rat-Embryo Cells Induced
In Vitro
by 3-Methylcholanthrene: Induction of Rat Leukemia Virus gs Antigen in Transformed Cells
Authors: Freeman Aaron E. , Gilden Raymond V. , Vernon Mina Lee , Wolford Ronald G. , Hugunin Patricia E. , Huebner Robert J.
Published: May 2006

Low-passage rat-embryo cells were not transformed by 3-methylcholanthrene or by 5-bromo-2′ deoxyuridine. However, prior treatment with bromodeoxyuridine, followed by treatment with methylcholanthrene, resulted in cell transformation about three subpassages after removal of the carcinogen. RNA-directed DNA polymerase activity could not be detected in either normal or transformed cells. However, gs-1 antigen specific for rat C-type RNA virus was detected in cultures derived from bromodeoxyuridine-treated cells. No gs-1 antigen for the C-type RNA virus was detected in cultures that had not been treated with bromodeoxyuridine during the 25 subpassages of these experiments.

High-passage rat-embryo cells, derived from a different cell pool, were transformed by either methylcholanthrene or dimethylbenzanthracene without prior infection with an exogenous virus, and without prior treatment with bromodeoxyuridine, gs-1 antigen for C-type RNA virus was also detected in 4 of 4 randomly selected transformed cell lines; the gs-1 antigen was not detected in any of 4 nontransformed control cultures. Considering these and previously published findings, we conclude that the lowpassage cells cannot be transformed by methylcholanthrene because of powerful cellular controls over the endogenous virus. Bromodeoxyuridine triggers some expressions of the endogenous virus; thus, the bromodeoxyuridine-treated cells are more susceptible to the transforming effects of methylcholanthrene. High-passage rat cells do not maintain perfect control over expression of their endogenous virus; the cell cultures are susceptible to the transforming effects of chemical carcinogens.
Enzyme Assay in Microsomes Below Zero Degrees
Authors: Debey Pascale , Balny Claude , Douzou Pierre
Published: May 2006

Reactions of a membrane-bound multienzyme complex (electron-transport chain of rat-liver microsomes) suspended in aqueous-organic solvent used as antifreeze at temperatures below 0° were studied. In the presence of a relatively high concentration of ethylene glycol, electron transfer can still be observed and some individual and sequential enzyme assays can be performed over a wide range of temperatures below 0°.
A Specific Photoreaction in Polydeoxyadenylic Acid
Authors: Pörschke Dietmar
Published: May 2006

Ultraviolet photosensitivity of the single-stranded forms of poly(A) and poly(dA) is compared. In contrast to poly(A), poly(dA) is rather sensitive to ultraviolet irradiation. Relatively low doses of ultraviolet light lead to characteristic changes of the ultraviolet and circular dichroism spectra of poly(dA), suggesting formation of a specific photoproduct in poly(dA) that cannot be formed in poly(A). The quantum yields in poly(dA) (ϕ = 2.5 × 10
-3
) are about a factor of 10 higher than in poly(A), indicating a high structure specificity. The base-pairing capacity of irradiated probes of poly(dA) to poly(dT) is inhibited. These results demonstrate a relatively high probability of DNA photolesions, that cannot be repaired by simple repair enzyme systems.
A Calcium Ionophore Simulating the Action of Epinephrine on the α-Adrenergic Receptor
Authors: Selinger Zvi , Eimerl Sara , Schramm Michael
Published: May 2006

Calcium acting through the ionophore A-23187 caused massive K
+
release from rat parotid slices. The ionophore thus simulates the action of epinephrine on the α-adrenergic receptor in this system. The α-adrenergic and cholinergic receptors are, however, not involved in the action of the ionophore since phetolamine and atropine had no effect on the ionophore-induced K
+
release. Amylase secretion, which is induced by epinephrine through the β-adrenergic receptor but does not require Ca
++
in the medium, was only slightly increased by the ionophore in the presence of Ca
++
. The K
+
released by Ca
++
through the ionophore was regained by the cells upon chelation of Ca
++
with ethylene glycol bis(β-aminoethyl ether)-
N,N
′-tetraacetic acid. Similar to the action of epinephrine on the α-adrenergic receptor, the K
+
release induced by the ionophore is specific for Ca
++
, which cannot be substituted by 2.5 mM Sr
++
, Mg
++
, or Ba
++
. The results suggest that epinephrine, like the ionophore, introduces Ca
++
into the cell to mediate K
+
release. It is proposed that the ionophore A-23187 may be an effective probe to test whether other Ca
++
-requiring hormones and neurotransmitters act in a similar fashion to produce their diverse physiological responses.
Crosslinking of the Glycoproteins in Human Erythrocyte Membranes
Authors: Ji T. H.
Published: May 2006

The glycoproteins of human erythrocyte membranes were crosslinked with dimethyl adipimidate dihydrochloride. On sodium dodecyl sulfate-polyacrylamide gel electrophoregrams of the crosslinked solubilized membranes, at least three new glycoprotein complexes appeared in addition to the normal glycoprotein species. One of the new glycoprotein complexes was shown to contain two of the three species of membrane glycoproteins.
Stringent Control of Ribosomal Protein Gene Expression in
Escherichia coli
Authors: Dennis Patrick P. , Nomura Masayasu
Published: May 2006

The regulation of the expression of ribosomal protein genes was examined during partial inhibition of tRNA aminoacylation in isogenic
rel
+
and
rel
-
strains of
E. coli
B carrying a temperature-sensitive mutation in valyl-tRNA synthetase (EC 6.1.1.9) gene. Measurements of the differential synthesis rate of ribosomal protein, α
r
(ribosomal protein synthesis rate/total protein synthesis rate), indicate that ribosomal protein synthesis is regulated directly or indirectly by availability of charged tRNA, and that the synthesis of ribosomal protein, like the synthesis of rRNA, is subject to the influence of the
rel
gene control system.
Prostaglandin Endoperoxides. A New Concept Concerning the Mode of Action and Release of Prostaglandins
Authors: Hamberg Mats , Svensson Jan , Samuelsson Bengt
Published: May 2006

Methods were developed for quantitative determination of the three major metabolites of arachidonic acid in human platelets, i.e., 12L-hydroxy-5,8,10,14-eicosatetraenoic acid (HETE), 12L-hydroxy-5,8,10-heptadecatrienoic acid (HHT) and 8-(1-hydroxy-3-oxopropyl)-9,12L-dihydroxy-5,10-heptadecadienoic acid (PHD). Aggregation of washed platelets by thrombin was accompanied by release of 1163-2175 ng/ml of HETE, 1129-2430 ng/ml of HHT, and 998-2299 ng/ml of PHD. The amount of PGG
2
(prostaglandin G
2
) produced as calculated from the sum of the amounts of its metabolites (HHT and PHD) was 2477-5480 ng/ml. In contrast, the amounts of PGE
2
(prostaglandin E
2
) and PGF
2α
(prostaglandin F
2α
) released were approximately two orders of magnitude lower. In this system, the prostaglandins thus exert their biological action through the endoperoxides, which are almost exclusively metabolized to nonprostanoate structures and only to a small extent to the classical prostaglandins.

Platelets from subjects given aspirin produced less than 5% of the above mentioned amounts of HHT and PHD, whereas the production of HETE was stimulated about 3-fold. This provides additional evidence for our earlier proposal [Hamberg, M., Svensson, J., Wakabayashi, T. & Samuelsson, B. (1974)
Proc. Nat. Acad. Sci. USA
71, 345-349] that the anti-aggregating effect of aspirin is through inhibition of PGG
2
formation.
Relaxation Complexes of Plasmids ColE1 and ColE2: Unique Site of the Nick in the Open Circular DNA of the Relaxed Complexes
Authors: Lovett Michael A. , Guiney Donald G. , Helinski Donald R.
Published: May 2006

The product of the induced relaxation of supercoiled DNA-protein relaxation complexes of colicinogenic factors E1 (ColE1) and E2 (ColE2) is an open circular DNA molecule with a strand-specific nick. Cleavage of the open circular DNA of each relaxed complex with the
Eco
RI restriction endonuclease demonstrates that the single-strand break is at a unique position. The site of the single-strand break in the relaxed ColE1 complex is approximately the same distance from the
Eco
RI cleavage site as the origin of ColE1 DNA replication.
Properties of the
Escherichia coli
DNA Binding (Unwinding) Protein: Interaction with DNA Polymerase and DNA
Authors: Molineux Ian J. , Gefter Malcolm L.
Published: May 2006

The
E. coli
DNA binding protein reduces the activity of the single-strand-specific nucleases associated with all three DNA polymerases known in
E. coli
. A slight excess of binding protein over that required to saturate the DNA template leads to total inhibition of activity of the 3′ → 5′ nucleases associated with DNA polymerases I and III, but restores maximum activity of the DNA polymerase II-associated nuclease. The binding protein forms a specific complex with DNA polymerase II in the absence of DNA, and it is this complex that degrades a DNA·binding protein complex. Binding protein also facilitates the binding of DNA polymerase II to single-stranded DNA, whereas the binding to DNA of DNA polymerase I is inhibited. These data may explain the specificity with which the binding protein enhances the synthetic ability of DNA polymerase II.
Stereochemical Evidence for the Evolution of Pyridoxal-phosphate Enzymes of Various Function from a Common Ancestor
Authors: Dunathan H. C. , Voet J. G.
Published: May 2006

Several pyridoxal-phosphate-dependent enzymes can convert the bound cofactor to pyridoxamine phosphate. This conversion may be an obligatory part of the normal catalytic sequence, as with transaminases, or may be an abnormal path, inactivating the enzyme. This conversion requires protonation of the C
4
′ carbon of the cofactor, which has now been shown to proceed stereospecifically and
with the same absolute stereochemistry
in seven quite different pyridoxal-phosphate enzymes. We report on one of these, tryptophan synthase B protein. This regularity in protonation stereochemistry suggests a remarkable regularity in the geometry of cofactor binding to the apoenzyme. This regularity is interpreted as evidence for the evolution of this entire family of enzymes from a common progenitor which, through the course of evolution, could not invert its original, arbitrary binding stereochemistry without passing through catalytically inactive conformations.
Diagonal Polyacrylamide-Dodecyl Sulfate Gel Electrophoresis for the Identification of Ribosomal Proteins Crosslinked with Methyl-4-Mercaptobutyrimidate
Authors: Sommer Andreas , Traut Robert R.
Published: May 2006

A diagonal polyacrylamide-dodecyl sulfate gel electrophoresis procedure is described. Its utility is related to the use of the reagent methyl-4-mercaptobutyrimidate as a protein-protein crosslinking reagent. Crosslinking with this reagent occurs through the formation of intermolecular disulfide bonds. Oxidized proteins are separated in one dimension by electrophoresis under non-reducing conditions and in the second dimension under reducing conditions. All proteins except those derived from crosslinked species fall on a diagonal. Methods are described for the identification of the separated monomeric components of crosslinked species. The technique has been applied to the 30S ribosomal subunit of
Escherichia coli
, and the new crosslinked dimer, S4-S13, has been identified.
Photo-Affinity Labeling of tRNA Binding Sites in Macromolecules. I. Linking of the Phenacyl-
p
-azide of 4-Thiouridine in (
Escherichia coli
) Valyl-tRNA to 16S RNA at the Ribosomal P Site
Authors: Schwartz Ira , Ofengand James
Published: May 2006

The phenacyl-
p
-azide of 4-thiouridine in (
E. coli
) tRNA
1
Val
was prepared for use as a photo-affinity probe of tRNA binding sites on ribosomes. The derivatized tRNA was 90-100% as active as control tRNA for aminoacylation, nonenzymatic binding to the ribosomal P site, elongation factor Tu(EFTu)-dependent binding to the A site, EFTu-GTP-aa-tRNA ternary complex formation, and transfer of valine into polypeptide. Irradiation of
p
-azidophenacyl-[
3
H]valyl-tRNA bound noncovalently to the ribosomal P site resulted in covalent attachment of 15-20% of the noncovalently bound tRNA to the ribosomes. The linking occurred exclusively to the 16S RNA of the 30S ribosomal subunit, thus suggesting that the region of the ribosome within 9 Å of the 4-thiouridine of tRNA, when it is bound in the P site, is solely 16S RNA.
Glutamate Oxidation in 6C3HED Lymphoma: Effects of L-Asparaginase on Sensitive and Resistant Lines
Authors: Lavietes Beverly B. , Regan David H. , Demopoulos Harry B.
Published: May 2006

L-Asparaginase (EC 3.5.1.1) inhibited respiration in sensitive, but not resistant, lines of murine lymphoma 6C3HED. Glucose, in these tumor lines, was principally converted to lactate, and very little was oxidized in the citric acid cycle or hexose monophosphate shunt. The cells derived 70-80% of their respiratory CO
2
from glutamine or glutamate. Asparaginase had no effect on the pattern of glucose utilization. The differential effect on oxygen consumption may result from the absence of asparagine synthetase in sensitive cells. Respiration may be inhibited by accumulation of the aspartate, the product of glutamate oxidation. Resistant lymphoma cells remove aspartate by converting it to asparagine. Sensitive cells, which lack asparagine synthetase, cannot make asparagine.
The Glycine Synaptic Receptor: Evidence That Strychnine Binding Is Associated with the Ionic Conductance Mechanism
Authors: Young Anne B. , Snyder Solomon H.
Published: May 2006

The ability of a series of anions to inhibit [
3
H]strychnine binding to spinal cord synaptic membranes correlates closely with their neurophysiologic capacity to reverse inhibitory postsynaptic potentials in the mammalian spinal cord. Seven neurophysiologically active anions are also effective inhibitors of [
3
H]strychnine binding with mean effective doses ranging from 160 to 620 mM. Seven other anions that are ineffective neurophysiologically also fail to alter strychnine binding. Chloride inhibits strychnine binding in a noncompetitive fashion. Hill plots of the displacement of [
3
H]strychnine by chloride give coefficients of 2.3-2.7. The inhibition of strychnine binding by these anions suggests that strychnine binding is closely associated with the ionic conductance mechanism for chloride in the glycine receptor.
Deficiencies or Excesses of Metabolites Interfering with Differentiation
Authors: Freese Ernst , Ichikawa Tomio , Oh Yong K. , Freese Elisabeth B. , Prasad Chandan
Published: May 2006

Auxotrophic mutants of
Bacillus subtilis
need much higher concentrations of the required adenine, nicotinic acid, riboflavin, thiamine, or tryptophan for optimal sporulation than for maximal growth. Acetate can partially replace thiamine, indicating the importance of the pyruvate dehydrogenase system for differentiation. A glycerol-requiring mutant can sporulate only if its cells contain a small concentration of L-α-glycerol phosphate during development. This can best be achieved by excess (≥5 mM) of extracellular α-glycerol phosphate, which enters
B. subtilis
very slowly. The results show that both biosynthetic and catabolic enzymes are often needed to maintain the precise balance of metabolites required for differentiation. Mutants unable to catabolize fructose 6-phosphate, glucose 6-phosphate, or α-glycerol phosphate do not sporulate as long as these compounds accumulate inside the cells; their development is blocked before prespore septa have formed.
Tubulin Synthesis on Polysomes Isolated from Brain and Leg Muscle of Embryonic Chick
Authors: Jorgensen Annelise Ø. , Heywood Stuart M.
Published: May 2006

A protein-synthesizing system has been established
in vitro
, in which tubulin is synthesized on polysomes isolated from brain and leg muscle of embryonic chick. The tubulin synthesized
in vitro
is characterized by (
i
) its electrophoretic mobility on sodium dodecyl sulfate-acrylamide gels (brain: 55,000 daltons; leg muscle: 53,000 daltons), and (
ii
) its ability to function as a microtubular subunit, as judged by its specific ability to participate in at least two polymerization and depolymerization steps in the microtubule assembly system
in vitro
.
Proton Magnetic Resonance Spectra of
Rhodospirillum rubrum
Cytochrome
C
2
Authors: Smith Gary M. , Kamen Martin D.
Published: May 2006

Nuclear magnetic resonance spectra of ferro- and ferricytochrome
C
2
from the facultative photoheterotroph,
Rhodospirillum rubrum
, obtained with a 220-MHz spectrometer, are presented. Assignments to protons of various important structural groups in contact with or near the prosthetic heme group are given. These include (
a
) in the ferro-form, methyl,
c
β and
c
γ protons of the extraplanar ligand residue, methionine 91, and methyl protons of the residue leucine 32; and (
b
) corresponding protons in the ferri-form with the addition of methyl protons from the condensation of a heme vinyl group with cysteine 17, a single proton from the condensation involving cysteine 14, and protons from the ring methyls. These resonances are compared with those corresponding to the same groups in horse heart cytochrome
c
.
Pyrrole Hydrogen Ionization of Imidazole Derivatives in Metal Ion Complexes and Carbonic Anhydrase
Authors: Martin R. Bruce
Published: May 2006

Zinc ion-induced pyrrole hydrogen ionization from a histidyl residue has recently been suggested as the source of the activity-related deprotonation in carbonic anhydrase (EC 4.2.1.1; carbonate hydro-lyase) occurring at pH 7-8. The results offered to support the hypothesis are shown to be deficient. Examination of the literature reveals no precedent for such a pronounced acidification from pK
a
[unk] 14.2 in imidazole compounds by zinc ion. It is suggested that Zn(II)-induced pyrrole ionizations in imidazoles occur with pK
a
about 13.