bluuebunny/crossref_metadata_2025 huggingface dataset:
Induction of deoxycytidine deaminase activity in mammalian cell lines by infection with herpes simplex virus type 1.
Authors: Chan T S
Published: May 2006

Herpes simplex virus type 1 induces deoxycytidine deaminase (cytidine/deoxycytidine aminohydrolase, EC 3.5.4.5) activity when it lytically infects a number of mammalian cell lines. The deaminase activity is induced in a mouse cell line that is deficient in this enzyme. The induction of the enzyme in this mutant cell line does not occur in the presence of actinomycin D and the induced enzyme is more thermolabile than the enzyme of the wild-type mouse cell line. Furthermore, a new deoxycytidine deaminase species with a characteristic electrophoretic mobility that is different from that of the host cell enzyme is found in cell extracts prepared from a human cell line infected with herpesvirus. These results strongly suggest that the virus-induced deoxycytidine deaminase is coded by the viral genome. Because a deficiency in this enzyme is conditionally lethal for cells growing in a medium containing 5-methyldeoxycytidine as the sole source of thymidylate, this enzyme can be utilized as a selective marker for selecting mutant cells that have regained deoxycytidine deaminase activity as the result of infection by ultraviolet-inactivated herpes simplex virus.
Regulation of heme pathway enzymes and cellular glutathione content by metals that do not chelate with tetrapyrroles: blockade of metal effects by thiols.
Authors: Maines M D , Kappas A
Published: May 2006

The trace metals nickel and platinum, which are not substrates for ferrochelatase and thus do not form heme in biological systems, were found to act similaryl to cobalt, and heme itself, in regulating heme metabolism in liver and kidney. These metals induced heme oxygenase activity in both organs with the peak of induced enzyme activity reached approximately 16 hr after single injections in rats. Both metals caused transient depression of cellular glutathione content followed by increases above normal after 12 hr in liver. Nickel and platinum were more potent inducers of heme oxygenase in kidney than in liver (10-13 times normal versus 5-6 times normal). At high concentrations, they inhibited heme oxygenase [heme, hydrogen-donor:oxygen oxidoreductase (alpha-methene-oxidizing, hydroxylating), EC 1.14.99.3] in vitro. Both were active in regulating heme metabolism only when administered in the ionic form. Complexing of the metals with sulfhydryl agents completely blocked their actions on heme metabolism. Administration of cysteine orally prior to or shortly after administration of the metals had a similar blocking effect. Nickel and platinum produced depression of delta-aminolevulinate synthase [succinyl-CoA:glycine c-succinyltransferase (decarboxylating), EC 2.3.1.37] activity in liver, but neigther inhibited this rate-limiting ennzyme for heme synthesis in vitro. Furthermore, despite the substantial decreases in cellular heme and hemoprotein contents mediated by the metal, production of delta-amimolevulinate synthase did not undergo the compensatory increase that would be expected if there were a direct reciprocal feedback relationship between cellular heme level and synthesis of this enzyme. These findings indicate that it is not necessary for metal ions to be chelated in the porphyrin ring in order to regulate the enzymes of heme synthesis and heme oxidation. Accordingly, it is suggested that the iron atom of heme is the proximately active regulator of delta-aminolevulinate synthase and heme oxygenase--actions generally ascribed to the iron-tetrapyrrole complex itself--and that the tetrapyrrole moiety of the complex functions primarily as a means of transport of the metal to regulatory sites in cells.
In vitro synthesis of messenger RNA by a defective interfering particle of vesicular stomatitis virus.
Authors: Colonno R J , Lazzarini R A , Keene J D , Banerjee A K
Published: May 2006

A defective interfering particle derived from the heat-resistant strain of vesicular stomatitis virus was analyzed for the presence of virion-associated RNA polymerase (nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) activtiy. The RNA synthesizing capacity of the defective particles in vitro was similar to that of the wild-type virus. Characterization of the RNA produced in vitro indicated that the defective particles were able to synthesize vesicular stomatitis virus leader RNA and four virus mRNA species that sediment at 12-18 S. These RNA products were identical to the mRNAs synthesized in vitro by the wild-type virus in regard to size, polyadenylation, capping, and methylation. In contrast to the wild-type virus, the purified defective particles did not synthesize the large mRNA species sedimenting at 31 S in vitro. Possible mechanisms of homotypic and heterotypic interferences shown by this defective particle are discussed.
Immune surveillance against virus-induced tumors and nonrejectability of spontaneous tumors: contrasting consequences of host versus tumor evolution.
Authors: Klein G , Klein E
Published: May 2006

Spontaneous tumours are defined as tumors that develop in the absence of all experimental interference. In contrast to the widely documented, strong rejection reactions against most virus-induced tumors, spontaneous tumors evoke little or no detectable rejection reaction in intact or preimmunized syngeneic hosts. The difference can be viewed in relation to the contrasting natural history of the two conditions. Spontaneous tumors evolve in several steps, as a fule. "Tumor progression" is a microevolutionary process at the level of the somatic tissue where successive clonal variants replace each other. Each new variant gains the upper hand due to its greater independence of some restricting host mechanism. Independence of immune restrictions must be part of this process. Host selection for immune resistance apparently plays no major role here, presumably because most of the naturally occurring tumors arise after the host has passed the peak of its reproductive period. Protection against the oncogenic effects of ubiquitous tumor viruses is, on the other hand, the result of host selection for immune mechanisms favoring prompt rejection of virus-transformed cells. This is neither synonymous with nor related to protection against the viral infection per se, which is frequently successful and usually quite harmless. A certain relationship can be perceived between the degree of viral ubiquity and the strength of immune protection against the corresponding tumor cells. Natural selection for host recognition of commonly occurring, virally induced changes in neoplastic cell membranes can be surmised to occur, at least in part, by the fixation of appropriate immune responsiveness (Ir) genes. The role of Ir genes for tumor recognition can be approached by the genetic analysis of the F1 hybrid resistance effect. Unresponsiveness to spontaneous tumors may be overcome by target-cell modification, e.g., by chemical coupling, somatic cell hybridization, or viral "xenogenization".
Evidence for a receptor protein of activated carcinogen
Authors: Mainigi Kumar D. , Sorof Sam
Published: May 2006

During carcinogenesis in rat liver by 3′-methyl-4-dimethylaminoazobenzene, the two moieties of the principal liver carcinogen-protein complex have considerably different turnover rates. With continued ingestion of the azocarcinogen by rats, the bound azo dye in the complex has a half-life of 2.5 ± 0.25 (SD) days, while the protein moiety has a half-life of 8.7 ± 1.6 days (probability of identity <0.001). In addition, the interaction of the azocarcinogen with the principal target protein
in vivo
appears to extend the half-life of the protein itself from 3.3 ± 0.2 days in normal liver to 8.7 ± 1.6 days (
P
< 0.001). The slowing of the turnover of the protein by the carcinogen appears to be readily reversible, since soon after the cessation of azocarcinogen feeding, the half-life of the protein returns to that of the target protein in normal liver.

The considerable difference in turnover rates of the two moieties of the complex and the reversible effects of the carcinogen in slowing the turnover of the protein moiety suggest that the two moieties of the native azoprotein are noncovalently linked and that they have different biological activities. The native complex appears to contain azo dye in an activated state that is capable of yielding a reactive electrophile, because after protein denaturation the bound azo dye was previously found to have properties that are indicative of covalent linkage to the protein. The retardation in the biological turnover rate of the protein moiety, apparently resulting from interaction with azocarcinogen, is in agreement with the known ligand-induced stabilization
in vitro
and reduced rate of proteolytic degradation
in vivo
of other proteins that result from conformational change to a more compact configuration. Our evidence is consistent with the hypothesis that the principal liver carcinogen-protein complex contains hydrophobically bound activated azocarcinogen, whose specificity of reaction with critical macromolecule(s) in nuclei may be directed by the conformationally altered protein of an activated carcinogen-protein complex, i.e., a specific receptor protein containing activated azocarcinogen.
Elastic model of supercoiling.
Authors: Benham C J
Published: May 2006

An elastic model for the supercoiling of duplex DNA is developed. The simplest assumptions regarding the elastic properties of double-helical DNA (homogeneous, isotropic, of circular cross section, and remaining straight when unstressed) will generate two orders of superhelicity when stressed. Recent experimental results [Brady, G.W., Fein, D.B. & Brumberger, H. (1976) Nature 264, 231-234] suggest that in supercoiled DNA molecules there are regions where two distinct orders of supercoiling arise, as predicted by this model.
Binding of 25-hydroxycholesterol and cholesterol to different cytoplasmic proteins
Authors: Kandutsch Andrew A. , Chen Harry W. , Shown Elaine P.
Published: May 2006

Studies were carried out to determine whether or not oxygenated derivatives of cholesterol (e.g., 25-hydroxycholesterol) that specifically suppress the activity of 3-hydroxy-3-methylglutaryl-CoA reductase [mevalonate:NADP
+
oxidoreductase (CoA-acylating), EC 1.1.1.34], bind to a soluble component of the cytoplasm different from that which binds the nonsuppressor, cholesterol. Density gradient fractionation of the cytosolic fraction isolated from L cell cultures that had been incubated with low concentrations of 25-hydroxy[
26,27
-
3
H]cholesterol or [
1,2
-
3
H]cholesterol provided evidence for the existence of at least two different sterol-binding proteins. Bound cholesterol sedimented in a sucrose density gradient as two or more broad bands with coefficients of approximately 9 S and 21 S. Two relatively narrow bands of bound 25-hydroxycholesterol had sedimentation coefficients of 5 S and 8 S. Preincubation of the cells with a relatively high concentration of unlabeled 25-hydroxycholesterol altered the banding pattern of the 25-hydroxy[
3
H]cholesterol taken up during a subsequent incubation period by decreasing the size of the major (8S) band. Under these conditions, cholesterol did not affect the banding pattern of 25-hydroxy[
3
H]cholesterol. The density gradient banding pattern of bound [
3
H]cholesterol was only slightly affected by preincubating the cells with unlabeled cholesterol or 25-hydroxycholesterol. Both sterols appeared to be bound to proteins because the bound sterols were eliminated from cytosol that had been heated at 100°, and their sedimentation coefficients were altered by proteolysis.
Decay of genetic variability in geographically structured populations.
Authors: Nagylaki T
Published: May 2006

The ultimate rate and pattern of approach to equilibrium of a diploid, monoecious population subdivided into a finite number of equal, large, panmictic colonies are calculated. The analysis is restricted to a single locus in the absence of selection, and every mutant is assumed to be new to the population. It is supposed that either the time-independent backward migration pattern is symmetric in the sense that the probability that an individual at position x migrated from y equals the probability that one at y migrated from x, or it depends only on displacements and not on initial and final positions. Generations are discrete and nonoverlapping. Asymptotically, the rate of convergence is approximately (I-u)2t[I-(2NT)-1]t, where u, NT, and t denote the mutation rate, total population size, and time in generations, respectively; the transient part of the probability that two homologous genes are the same allele is approximately independent of their spatial separation. Thus, in this respect the population behaves as if it were panmictic.
Enhanced oncogenic behavior of human and mouse cells after cellular hybridization with Burkitt tumor cells.
Authors: Glaser R , Ablashi D V , Nonoyama M , Henle W , Easton J
Published: May 2006

Studies were made of the expression of the Epstein-Barr virus (EBV) in somatic hybrids of Burkitt tumor cells and human or mouse cells to determine whether EBV genetic information associated with the capacity to transform leukocytes of human and non-human primates could be maintained and expressed in nonlymphoblastoid cells. Data obtained thus far suggest that at least one characteristic associated with cellular transformation (loss of contact inhibition) is expressed only in nonlymphoblastoid cells in which the EBV genome is maintained. In addition, we have demonstrated that human epithelial/Burkitt hybrid cells (D98/HR-1 and D98/Raji) are more oncogenic in nude (athymic) mice than are cells of the human epithelial parental line, D98, or one of the Burkitt lymphoblastoid parent cell lines (Raji); the HR-1 Burkitt parent cell line was as oncogenic as the hybrid cell lines but the time required to induce tumors was much longer. Thus, human epithelial cells show alteration of growth properties in vitro and in vivo after cellular hybridization with Burkitt tumor cells.
Discontinuous replication of replicative form DNA from bacteriophage phiX174.
Authors: Machida Y , Okazaki T , Okazaki R
Published: May 2006

Bacteriophage phiX174 DNA has been labeled with short pulses of [3H]thymidine during synthesis of replicative form molecules in infected Escherichia coli HF4704 cells. The replicating phiX174 DNA was isolated and analyzed by sedimentation in an alkaline sucrose gradient. During a brief pulse (5 sec at 30 degrees), the radioactivity incorporated into the complementary strand was found in chains much shorter than one genome length. Of the radioactivity incorporated into the viral strand, two-thirds was in the short pieces and the rest was in chains of one genome length or longer. RNA attachment to the 5' end of both strand components of the nascent short pieces was shown by the appearance of spleen exonuclease-digestable nascent molecules after alkali treatment. These observations suggest that the viral as well as the complementary strand is synthesized by the discontinuous mechanism with RNA primers during replication of duplex phiX174 DNA.
Isoantigenic expression of Forssman glycolipid in human gastric and colonic mucosa: Its possible identity with “A-like antigen” in human cancer
Authors: Hakomori S. , Wang S.-M. , Young W. W.
Published: May 2006

The heterogenetic Forssman antigen is a glycosphingolipid, a ceramide pentasaccharide with the structure GalNAcα1→3GalNAcβ1→3Galα1→4Galβ1→4Glc→ceramide. Forssman-positive animals are capable of synthesizing this compound in tissues or in erythrocytes, in contrast to the Forssman-negative species, including humans, which are incapable of adding the last carbohydrate in the sequence of the Forssman antigen, namely αGalNAc. The Forssman glycolipid and its precursor globoside were examined in twenty-one samples of surgically extirpated gastrointestinal mucosa and tumors derived therefrom. The results revealed that a few patients had chemically and immunologically detectable levels of the Forssman glycolipid as a normal component of their gastrointestinal mucosa (F
+
population); in contrast, the majority of patients did not contain this glycolipid in their normal mucosa (F
-
population). Whereas the F
-
population included blood groups A, B, and O, the F
+
population did not correspond to blood group A. The Forssman status in tumors taken from the F
+
or F
-
population showed the following striking features: (
i
) all tumors derived from F
-
mucosa possessed Forssman glycolipid, whereas (
ii
) none of the tumors originating in F
+
mucosa contained Forssman glycolipid. Globoside, the immediate precursor of Forssman antigen, was distributed equally among F
+
and F
-
mucosa and the tumors derived therefrom. Thus, the expression of Forssman antigen in gastrointestinal mucosa appears akin to that of an isoantigen. Furthermore, the Forssman antigen that appears in tumors of the F
-
population could represent a human tumor-associated antigen. In view of the strong crossreactivity of Forssman antigen with blood group A determinants, the appearance of Forssman antigen in human tumors could be related to the “A-like antigen” (or “neo-A antigen”) of human tumors reported previously [Hakomori, S., Koscielak, J., Black, K. J. & Jeanloz, R. W. (1967)
J. Immunol
. 98, 31-38; Häkkinen, I. (1970)
J. Natl. Cancer Inst
. 44, 1183-1193].
Variation in ability of measles virus plaque progeny to induce interferon.
Authors: McKimm J , Rapp F
Published: May 2006

Plaque progeny of three interferon (IF)-inducing strains of measles virus (Edmonston, Schwarz, and CC) were examined for ability to induce IF in BSC-1 cells. Only after passage in Vero cells did any of the Edmonston progeny induce IF. The vast majority of plaque progeny selected from the Schwarz strain induced IF, even though this virus was originally derived from the Edmonston strain. This property was retained even after serial plaque purification of the progeny. However, the Schwarz-derived CC strain consisted of a population generally unable to induce IF. Stocks grown from both Edmonston and CC plaques demonstrating the IF+ phenotype maintained this characteristic as a whole, but it was not a property that was inherited by all progeny in the stocks. Levels of IF induced were approximately the same for all strains, even though the proportion of inducing progeny varied markedly among them. These noninducing variants appeared to be normal, fully infectious measles virions. The results suggest that induction of IF by measles virus is at least partially under the genetic control of the virus.
An observation concerning electronically excited retinal
Authors: Simons Jack
Published: May 2006

The observation of Mathies and Stryer of highly polar excited electronic states of
all-trans
-retinal, its unprotonated Schiff base, a salt of the protonated Schiff base, and 11-
cis
-retinal leads us to propose a possible consequence of the existence of such species. The highly polar excited molecule may have sufficient potential to oxidize its surroundings, thus achieving a transfer of one electron. Experimental evidence is combined with crude model calculations to support the possible role of these excited states as electron transfer agents.
Influence of 9-beta-D-arabinofuranosyladenine on total protein synthesis and on differential gene expression of unique proteins in the rodent malarial parasite Plasmodium berghei.
Authors: Ilan J , Pierce D R , Miller F W
Published: May 2006

The antibiotic 9-beta-D-arabinofuranosyladenine is a drug with a broad spectrum of activity against animal viruses, with little or no effect on mammalian cells, when administered in vivo or in vitro. Here we report that the antibiotic markedly inhibited the incorporation of [35S]methionine into malarial protein. Inhibition was apparent when the parasites were either exposed to the drug in vivo during the course of infection or incubated with the drug in vitro. Moreover, the antibiotic induced pronounced changes in the spectrum of proteins synthesized. Some proteins that are prominently apparent in the control disappear from the drug-treated parasites; others specific for drug-treated parasites appear, indicating changes in the commitment for gene expression as manifested by the appearance of the final protein product. Proteins synthesized were analyzed by two-dimensional polyacrylamide gels; the first dimension used isoelectric focusing in cylinder gels and the second dimension used electrophoresis in a lithium dodecyl sulfate slab gel. Proteins were visualized by radioautography.
Random assembly of different kinds of small subunit polypeptides during formation of fraction I protein macromolecules
Authors: Hirai Atsushi
Published: May 2006

Maternal inheritance determine the charge on the large subunit of fraction I protein whereas both parents of an interspecific F
1
hybrid plant make an equal contribution to the charge of the small subunit. Experiments were performed to test whether fraction I protein in the hybrid plant was a hybrid molecule or two kinds of protein molecules, one composed of large subunits combined with small subunits of the male type and the other composed of large subunits combined with small subunits of the female type. A mixture of fraction I proteins from
Nicotiana langsdorffii
and
N. bonariensis
was resolved into two components of different charge by agarose gel electrophoresis but the protein from the F
1
hybrid plant between the two species was a single component. However, two-dimensional agarose gel electrophoresis showed that fraction I protein from an F
1
hybrid could be highly heterogeneous in charge compared to a fraction I protein containing a single small subunit polypeptide that was homogeneous in charge. Evidently, charge heterogeneity results from random self-assembly of the small subunit polypeptides. Random self-assembly of small subunits of two types could result in a mixture in which 99.2% of the population are hybrid molecules composed of seven types together with 0.39% containing small subunits of the maternal type and 0.39% containing those of the paternal type. In an F
1
hybrid plant in which three small subunit polypeptides randomize during assembly, a mixture of 45 types of fraction I protein macromolecules could be present.
Genetic analysis of host range mutant viruses suggests an uncoating defect in simian virus 40-resistant monkey cells
Authors: Wilson John H.
Published: May 2006

Host range mutations that permit simian virus 40 (SV40) to grow with increased efficiency on SV40-resistant monkey cells have been positioned within the viral
B/C
gene by a mapping method that relies on the coupling of specific DNA fragments. Pairs of restriction endonucleases that each cleave SV40 DNA at only one site were used to generate pairs of specific DNA fragments. Corresponding pairs of fragments were purified from host range mutant and wild-type DNA and joined in known combinations to determine the location of the host range mutations. The map position of the host range mutations was confirmed by using the same technique to generate and couple genetically marked viral DNA fragments to produce the predicted double mutants. Three different double mutants were constructed that carry both host range and temperature-sensitive
A
mutations. The mutations in three independently isolated host range mutant viruses are located at very close, perhaps identical, sites, because no wild type viruses were produced from the cell-mediated repair of pairwise heteroduplexes between them. The location of these host range mutations suggests that their phenotype results from mutational alteration of the major capsid protein, the product of the
B/C
gene.

In addition it was demonstrated that monkey cells can efficiently join appropriate pairs of restriction endonuclease fragments intracellularly to produce infectious genomes. That reaction has been partially characterized. The general utility of fragment coupling (
in vitro
and
in vivo
) and heteroduplex repair for constructing and analyzing multiple mutants of SV40 is discussed.
Hybridization properties of immunoglobulin mRNA: Failure to detect covalently associated IgG mRNA transcripts of reiterated and unique mouse DNA
Authors: Legler Mary K. , Cohen Edward P.
Published: May 2006

Messenger RNAs for antibody heavy (γ) and light (κ) chains were isolated from the polysomes of an IgG-producing mouse myeloma cell line. Polysomes engaged in heavy or light chain synthesis were separated by immunoprecipitation using rabbit antibodies specific for the mouse IgG formed. The mRNAs obtained, more than 85% specifying IgG [Legler, M. & Cohen, E. P. (1976)
Biochemistry
15, 4390-4399], were used as “probes” in hybridization experiments with sheared mouse liver DNA. To determine whether mRNAs for Ig heavy and light chains contained covalently bound transcripts of unique and reiterated DNA, hybrids were isolated with or without treatment with ribonuclease (RNase) prior to fractionation and the apparent rates of hybridization were compared. A monophasic C
o
t (DNA concentration × incubation time) curve with a C
0
t
1/2
of 4000 moles of nucleotide per liter × sec, corresponding to less than five hybridization sites per haploid genome, was obtained whether or not RNase was used in the isolation protocol. With a similar experimental design, the apparent hybridization rates of heterogeneous nuclear RNA from the same cell source were clearly different.

The “stringency” of the reaction was reduced by incubating the hybridization mixtures at lower temperatures in a further attempt to detect a large class of repetitive sequences that would form hybrids with the IgG mRNA used, if such sequences were present. The results, however, were the same; i.e., the apparent rates of hybridization of mRNAs for mouse antibody γ and κ chains with sheared mouse liver DNA were essentially the same whether or not RNase was used in the isolation procedure. Reiteration of genes in mouse liver DNA for mouse IgG could not be detected.
DNA packaging and the pathway of bacteriophage T4 head assembly.
Authors: Hsiao C L , Black L W
Published: May 2006

A cold-sensitive mutation in the structural gene for a minor phage T4 capsid protein (p20) leads to formation of heads containing p20 and cleaved head proteins and empty of DNA. Such heads can be filled with DNA and converted to active phages in vivo uponshift to high temperature. It appears that p20 has two distinct roles in head assembly: first, in construction of the prehead shell (blocked by ts and am mutation) and, second,in DNA packaging (blocked by cs mutation). The latter function is closely associated with gene 17 product, previously known to be required for DNA packagaing. Temperature shift studies of cs-ts double mutants and other observations allow determination of phage function required for DNA packaging. Contrary to previous proposals, we find that T4 DNA packaging is not directly coupled to and can follow DNA synthesis, protein cleavage, prehead core removal, and gene 21-mediated cleavage-induced increase in head volume. Our evidence suggests that an altered head assembly pathway exists and that DNA packaging is probably initiated by DNA-capsid (p20) interaction.
Antibodies to estrogen receptor: Immunochemical similarity of estrophilin from various mammalian species
Authors: Greene Geoffrey L. , Closs Liselotte E. , Fleming Honorée , DeSombre Eugene R. , Jensen Elwood V.
Published: May 2006

Immunoglobulin obtained from the serum of rabbits immunized with a highly purified preparation of estradiol-receptor complex from calf uterine nuclei has been shown to contain specific antibodies to the receptor protein (estrophilin) by four criteria: (
a
) precipitation of the radioactive steroid upon addition of goat antibody against rabbit gamma globulin to a mixture of the tritiated estradiol-receptor complex and the immunoglobulin, (
b
) adsorption of the estradiol-receptor complex by the immunoglobulin linked to Sepharose, (
c
) adsorption of the estradiol-receptor complex in the presence of the immunoglobulin by
Staphylococcus aureus
protein-A linked to Sepharose, and (
d
) the ability of the immunoglobulin to increase the sedimentation rate of the estradiol-receptor complex. Antibodies to calf nuclear estrophilin were shown to crossreact with the nuclear receptor of rat uterus, as well as with the extranuclear receptor of calf, rat, mouse, and guinea pig uterus and of human breast cancer. The antibodies do not react with either the nuclear or extranuclear dihydrotestosterone-receptor complexes of rat prostate or with the extranuclear progesterone-receptor complex of chick oviduct. These findings indicate an immunochemical similarity among estrophilins from several mammalian species, as well as between extranuclear and nuclear forms of the receptor, but not among receptor proteins for different steroid hormones.
Spin labeling of a cysteine residue of the
Escherichia coli
outer membrane lipoprotein in its membrane environment
Authors: Lee Nancy , Scandella Carl , Inouye Masayori
Published: May 2006

A method was developed to attach a spin label to a specific site on the structural lipoprotein of the
Escherichia coli
outer membrane
in situ
. This method takes advantage of the fact that the outer membrane of wild-type
E. coli
contains few residues reactive towards sulfhydryl reagents. A mutant
E. coli
strain has been isolated [Suzuki, H., Nishimura, Y., Iketani, H., Campisi, J., Hirashima, A., Inouye, M. & Hirota, Y. (1976)
J. Bacteriol.
127, 1494-1501] in which the second position from the carboxy terminus of the lipoprotein is changed from arginine into a cysteine residue. The membrane fraction of this mutant was treated with
N
-(1-oxyl-2,2,5,5-tetramethylpyrrolidinyl)maleimide in the presence of EDTA and 2-mercaptoethanol. Spin label was found to be preferentially incorporated into the lipoprotein. The spectrum of the spin-labeled membrane shows two components, both arising from spin label at the same site near the carboxy terminus. The strongly immobilized component has a maximum hyperfine splitting value of 53 G, and the weakly immobilized component, 37 G. A fraction of the lipoprotein is covalently bound to the peptidoglycan layer through its carboxy-terminal lysine; the spectrum of the isolated bound form of the lipoprotein was identical to that of the free form. When the matrix protein, the other major outer membrane protein, was removed by mutation, the spectrum of the lipoprotein was altered, suggesting that these two proteins are closely associated.
Translational specificity of Bacillus stearothermophilus ribosomes.
Authors: Chen C S , Nakamoto T
Published: May 2006

The translational specificity of Bacillus stearothermophilus ribosomes was studied by determining the effectiveness of various synthetic RNAs as templates at 37 degrees and at higher temperatures. The effectiveness of poly(G,U) was maximal at a G:U ratio of 1:3; it declined with lower G content because of reduced ribosomal affinity for the RNA and, with higher G, because of interference by secondary structure. The effectiveness of poly(A,C,G,U) also declined when secondary structure was increased by increasing (G+C) content. Escherichia coli ribosomes exhibited a similar specificity for poly-(G,U), but had a lower sensitivity to interference by RNA secondary structure. In both bacterial species, sensitivity to secondary structure was determined by the 30S ribosomal subunit.
Evidence for the presence of two nonidentical subunits in NAD-dependent isocitrate dehydrogenase of pig heart
Authors: Ramachandran N. , Colman Roberta F.
Published: May 2006

The NAD-dependent isocitrate dehydrogenase [
threo
-D
S
-isocitrate:NAD
+
oxidoreductase (decarboxylating); EC 1.1.1.41] from pig heart is a multisubunit enzyme with a molecular weight of approximately 340,000. Electrophoresis of the enzyme in 10% polyacrylamide gels containing sodium dodecyl sulfate reveals two discrete bands with molecular weights of 41,000 and 39,000. The two bands exhibit approximately equal intensity when stained with Coomassie Blue, Amido Black, and Bromophenol Blue, suggesting that these polypeptide chains are present in equimolar quantities in the native enzyme. The same two-band pattern is observed when the sulfhydryl groups of the enzyme are blocked by alkylation with iodoacetate prior to electrophoresis, indicating that sulfhydryl oxidation is not responsible for the observed heterogeneity. Each of the subunits appears as a single band when eluted from the gel and again subjected to electrophoresis under the same conditions. Isocitrate dehydrogenase contains a total of 41 lysine and arginine residues per average subunit of 40,000 daltons. The observation of approximately 80 peptides upon paper chromatography and high voltage electrophoresis of tryptic digests of the enzyme is consistent with the existence of two distinct polypeptide chains. Dansylation yields two NH
2
-terminal amino acid derivatives: dansyl-phenylalanine and dansyl-alanine. It is concluded that the NAD-specific isocitrate dehydrogenase is composed of equal numbers of two nonidentical subunits.
Subcellular fractionation of intra-axonally transport polypeptides in the rabbit visual system.
Authors: Lorenz T , Willard M
Published: May 2006

We analyzed the subcellular distributions of proteins that are transported down the axons of rabbit retinal ganglion cells and compared these distributions to those of enzyme markers for endoplasmic reticulum, plasma membrane, and mitochondria. The proteins of each of five previously identified transport groups were uniquely distributed through the subcellular fractions, suggesting that each transport group is associated with different subcellular organelles. In particular, all of the observed group I polypeptides (the most rapidly moving, group, maximum velocity greater than 240 mm/day) were associated with material of hydrodynamic properties similar to those of the plasma membrane. The proteins of group II (maximum velocity = 34--68 mm/day) were heterogenous in their subcellular distributions but included mitochondrial proteins. Groups III and IV (maximum velocity = 4--8 and 2--4 mm/day, respectively) included materials that may be involved in motile processes; group V (maximum velocity = 0.7--1.1 mm/day) contained material of very high density which may be associated with neurofilaments.
Transcription of a defective polyoma virus genome.
Authors: Condit R , Cowie A L , Kamen R , Fried M
Published: May 2006

The circular genome of the cloned defective polyoma virus D-50 consists of tandemly repeated copies of the DNA sequence between 67 and 84 units on the wild-type polyoma virus DNA map. Each repeated copy thus contains the origin of viral DNA replication, which is located at about 71 map units. Viral RNA was synthesized in vitro using viral transcription complexes extracted late (30 hr) after infection from mouse cells co-infected with D-50 and helper wild-type virus. Both wild-type and D-50 DNA molecules were active as templates for in vitro transcription. Approximately 84% of the RNA transcribed in vitro from wild-type DNA was complementary to the L DNA strand. This is normal for wild-type transcription late after infection. By contrast, at least 90% of the RNA transcribed from D-50 DNA molecules was complementary to the E DNA strand. After normalization of the data to account for the observed molar ratio of D-50 DNA repeated sequences to unit length wild-type DNA, we estimate that transcription of the E DNA strand of each D-50 repeated unit is about 1.4 times as efficient as transcription of the wild-type E DNA strand. Transcription of the D-50 L DNA strand, however, is only 0.03 times as efficient as transcription of the wild-type L DNA strand. The implications of these results concerning the nature and location of promoter sequences in polyoma DNA are discussed.
Ovalbumin: a secreted protein without a transient hydrophobic leader sequence.
Authors: Palmiter R D , Gagnon J , Walsh K A
Published: May 2006

Ovalbumin mRNA was translated in a reticulocyte lysate. The primary translation product starts with methionine derived from Met-tRNAf. When the nascent polypeptide is about 20 residues long, this methionine is removed. The new NH2-terminal glycine is acetylated from acetyl-CoA when the polypeptide is 44 residues long. The sequence of 35 residues at the NH2 terminus of ovalbumin was determined by automated Edman degradation after a method was devised to prevent acetylation during protein synthesis in the reticulocyte lysate. This sequence is the same as that of secreted ovalbumin and does not resemble the transient "signal peptides" associated with most secretory proteins, including three other egg white proteins synthesized in the same cells as ovalbumin.
Hysteresis effects of C
1
H
4
and C
2
H
4
in the regions of the solid-phase transitions
Authors: Ma Shao-mu , Lin S. H. , Eyring Henry
Published: May 2006

The thermodynamic model of hysteresis in phase transitions based on the regular solution theory, previously developed, was applied to the solid phases of C
1
H
4
and C
2
H
4
. The width and height of the hysteresis loops for these systems were calculated and compared with the experimental data; agreement was satisfactory.
Complete nucleotide sequence of a 16S ribosomal RNA gene from Escherichia coli.
Authors: Brosius J , Palmer M L , Kennedy P J , Noller H F
Published: May 2006

The complete nucleotide sequence of the 16S RNA gene from the rrnB cistron of Escherichia coli has been determined by using three rapid DNA sequencing methods. Nearly all of the structure has been confirmed by two to six independent sequence determinations on both DNA strands. The length of the 16S rRNA chain inferred from the DNA sequence is 1541 nucleotides, in close agreement with previous estimates. We note discrepancies between this sequence and the most recent version of it reported from direct RNA sequencing [Ehresmann, C., Stiegler, P., Carbon, P. & Ebel, J.P. (1977) FEBS Lett. 84, 337-341]. A few of these may be explained by heterogeneity among 16S rRNA sequences from different cistrons. No nucleotide sequences were found in the 16S rRNA gene that cannot be reconciled with RNase digestion products of mature 16S rRNA.
Glucose-induced conformational change in yeast hexokinase.
Authors: Bennett W S , Steitz T A
Published: May 2006

The A isozyme of yeast hexokinase (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1) crystallized as a complex with glucose has a conformation that is dramatically different from the conformation of the B isozyme crystallized in the absence of glucose. Comparison of the high-resolution structures shows that one lobe of the molecule is rotated by 12 degrees relative to the other lobe, resulting in movements of as much as 8 A in the polypeptide backbone and closing the cleft between the lobes into which glucose is bound. The conformational change is produced by the binding of glucose (R.C. McDonald, T.A. Steitz, and D.M. Engelman, unpublished data) and is essential for catalysis [Anderson, C.M., Stenkamp, R.E., McDonald, R.C. & Steitz, T.A. (1978) J. Mol. Biol. 123, 207-219] and thus provides an example of induced fit. The surface area of the hexokinase A-glucose complex exposed to solvent is smaller than that of native hexokinase B. By using the change in exposed surface area to estimate the hydrophobic contribution to the free energy changes upon glucose binding, we find that the hydrophobic effect alone favors the active conformation of hexokinase in the presence and absence of sugar. The observed stability of the inactive conformation of the enzyme in the absence of substrates may result from a deficiency of complementary interactions within the cavity that forms when the two lobes close together.
Macronuclear DNA of the hypotrichous ciliate
Oxytricha fallax
Authors: Rae Peter M. M. , Spear Brian B.
Published: May 2006

DNA in the macronuclei of
Oxytricha fallax
, as in other hypotrichous ciliate protozoa, exists as small, achromosomal molecules rather than in chromosomes. We report studies on
O. fallax
DNA using physicochemical procedures and nucleic acid hybridization. Macronuclear DNA molecules range in size from 22 kilobase pairs (kb) to about 0.5 kb. The DNA has a buoyant density in CsCl of 1.694 g·cm
-3
and a melting temperature in 15 mM NaCl/1.5 mM sodium citrate, pH 7, at 65.4°. These values correspond to 34.7% Gua + Cyt and 28.1% Gua + Cyt, respectively, and base composition determined by thin-layer chromatography of nucleotides is 32.4% Gua + Cyt. The only modified nucleotide that is detectable is
N
6
-methyldeoxyadenylate (0.2%), and the amount and kind of modification cannot account for the discrepancies in nucleotide composition determination by the three methods. The genes for 25S and 19S rRNA are contained in DNA molecules 6.67 kb in length, of which at least 6.15 kb is transcribed. These rDNA molecules show no intrastrand complementarity as does rDNA in some other lower eukaryotes, and they have two asymmetric sites recognized by endonuclease
Eco
RI. The genes for 5S RNA are in DNA molecules 0.69 kb in length. Digestion of this DNA with restriction enzymes
Bam
HI,
Bsu
I,
Hha
I, and
Taq
I gives no evidence for a tandemly repeated sequence. It is likely that both 19S + 25S rRNA genes and 5S RNA genes in the
Oxytricha
macronucleus exist as single transcription units, and both may have “spacer” regions approximately 0.5 kb long.
Viscoelastic studies on Tetrahymena macronuclear DNA.
Authors: Williams J B , Fleck E W , Hellier L E , Uhlenhopp E
Published: May 2006

We have used viscoelastometry in an attempt to understand the physical organization of genetic material in Tetrahymena nuclei. The micronucleus or germ line nucleus is diploid. It divides mitotically during vegetative growth, and five pairs of chromosomes are seen in meiosis. The macronucleus, or somatic nucleus, is approximately 45-ploid, divides amitotically, and has no visible chromosomes at any stage. Viscoelastic analysis of Tetrahymena macronuclei reveals DNA Molecules of 2-3 X 10(10) daltons accounting for much, if not all, of the macronuclear DNA. Since the average chromosome in the micronucleus contains 2.4-2.7 X 10(10) daltons of DNA, we deduce that the macronucleus of Tetrahymena contains chromosome-sized DNA molecules.
Colored lattices
Authors: Harker David
Published: May 2006

Combinations of translations and color permutations are derived that leave a periodic array of colored points—a colored lattice—apparently unchanged. It is found that there are three types of colored lattices: (
1
) those in which all rows and nets have more than one color, (
2
) those in which there are rows with only one color, and (
3
) those in which there are both rows and nets with only one color. The color permutation groups of colored lattices are all Abelian. The direct product of three independent cyclic subgroups is required by type
1
, but only two are required by type
2
; in type
3
the color permutation group consists of the
n
powers of a cyclic permutation of all
n
colors present—i.e., the group consists of a single cycle.
Some new singular Fourier—Stieltjes series
Authors: Brown Gavin , Hewitt Edwin
Published: May 2006

Singular continuous probability measures on the circle group are constructed whose Fourier-Stieltjes transforms converge to zero very rapidly and also have positive partial sums. Partial results for the line and for arbitary compact infinite Abelian groups are also obtained.
On the failure of the Drell-Yan parton model to account for production of the
J
/Ψ in nucleon-nucleon interactions
Authors: Adair Robert K.
Published: May 2006

We calculate the cross sections for the production of the
J
/Ψ in nucleon-nucleon interactions on the basis of a naive Drell-Yan-type parton model where the Ψ production is considered as production through the resonant or fusion interaction of quarks and antiquarks resident in the colliding nucleons. The interacting quarks are assumed to act as free point Dirac particles obeying the Bethe-Heitler description of annihilation to lepton pairs. Unitarity limits on Ψ production established by calculations conducted on this basis are shown to be much smaller than the measured cross section, indicating that such models are unsatisfactory. Similar considerations suggest that the Ψ production cannot be described by the interactions of nearly free gluons.
Fertility repression of F-like conjugative plasmids: Physical mapping of the R6-5
finO
and
finP
cistrons and identification of the
finO
protein
Authors: Timmis Kenneth N. , Andrés Isabel , Achtman Mark
Published: May 2006

The locations of the fertility inhibition genes
finO
and
finP
of the F-like conjugative multiple antibiotic-resistance plasmid R6-5 have been determined. As found previously for that of the fertility plasmid F, the
finP
gene of R6-5 is located close to the origin of DNA transfer,
oriT
, and to the promoter-proximal segment of the
tra
operon. Thus,
finP
is close to the site of action of the FinOP fertility inhibition system. In contrast, the
finO
gene is located on the other side of the
tra
operon, greater than 35 kilobases from the
finP
gene;
finO
is very close to the origin of vegetative replication,
oriV
, and to cistrons encoding functions involved in autonomous plasmid replication and plasmid incompatibility. A 4.5-kilobase fragment of R6-5 DNA containing the
finO
gene has been cloned on the high-copy amplifiable vector plasmid pBR322. This hybrid plasmid, designated pKTO31, causes severe repression of conjugal transfer of plasmid F, indicating the production of high cellular levels of finO protein. Two independent
finO
mutant derivatives were obtained after mutagenesis of the pKTO31 plasmid. Comparison of proteins synthesized by minicells carrying
finO
-
mutant plasmids with those carrying various
finO
+
plasmids enables the
finO
gene product to be tentatively identified as a 22,000-dalton protein.
Decrease in functional albumin mRNA during estrogen-induced vitellogenin biosynthesis in avian liver.
Authors: Williams D L , Wang S Y , Klett H
Published: May 2006

Translation of rooster liver RNA in a wheat germ extract is shown to yield albumin as one of the cell-free products. Quantitation of albumin mRNA by the translation assay indicates that functional albumin mRNA represents 10% of total liver mRNA activity in control roosters. After estrogen administration, this level decreases in a continuous fashion until functional albumin mRNA represents 5% of total mRNA activity at 12 days. This decrease in functional albumin mRNA was correlated with several parameters of vitellogenin induction. Functional vitellogenin mRNA increases to a maximum at 4 days after hormone treatment and returns to control levels by 12 days. A similar pattern is seen for the hormone-stimulated increase in total mRNA activity. The decrease in functional albumin mRNA, therefore, persists after the vitellogenic response of the liver has been completed. These results suggest that the decrease in hepatic albumin synthesis after hormone treatment is due to an estrogen-mediated decrease in the content of albumin mRNA.
Methionine analogs and cell division regulation in the yeast Saccharomyces cerevisiae.
Authors: Singer R A , Johnston G C , Bedard D
Published: May 2006

Methionine analogs such as ethionine, selenomethionine, and trifluoromethionine all arrest growth and division of the yeast Saccharomyces cerevisiae. One analog, ethionine, caused cells of the yeast to arrest specifically within G1; reciprocal shift experiments showed that ethionine and alpha-factor arrested cells at the same step ("start"). The major effect of ethionine on synthesis of macromolecules was to reduce both the rate of appearance of 35S ribosomal precursor RNA and the rate of production of mature rRNA. Synthesis of protein was relatively unaffected by ethionine. Selenomethionine and trifluoromethionine caused cells to arrest randomly in the cell division cycle. Although treatment of cells with either selenomethionine or trifluoromethionine also reduced the rate of total RNA synthesis, each of these analogs had other effects that presumably prohibited completion of the cell cycle. We propose that the rate of rRNA production is an important regulatory event in the cell cycle.